Prolactin may help in liver regeneration

Thursday 17 October 2013 - 1am PST

The hormone prolactin is probably best known for its role in stimulating milk production in mothers after giving birth. But prolactin also has an important function in the liver. This organ has the highest number of prolactin receptors in the body, ports that allow this hormone to enter liver cells. There, prolactin signals these cells to multiply and new blood vessels to grow to fuel this organ's expansion.

Wondering if these properties might be useful to encourage the liver to regrow after surgery to remove part of it - sometimes necessary to treat cancer or other liver diseases, or to donate liver tissue for transplants - Carmen Clapp of the Universidad Nacional Automoma de Mexico and her colleagues worked with animal models on both ends of a prolactin spectrum: rats that overproduced the hormone, and mice specially bred to have no prolactin receptors, the equivalent of a dearth of the hormone since prolactin can't enter these animals' cells.

The researchers found that the animals with extra prolactin had larger livers, regenerated their livers faster after partial removal, and were significantly more likely to survive that liver surgery compared to the animals that couldn't process prolactin.

The article is entitled "Prolactin Promotes Normal Liver Growth, Survival, and Regeneration in Rodents." It appears in the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, published by the American Physiological Society.

Methodology

The researchers made rats overproduce prolactin by implanting two extra anterior pituitary glands - the gland that produces prolactin - in the animals' backs. To make sure the surgery itself wasn't responsible for any effects they saw, they compared these rats to others that had a sham surgery, in which they made incisions but didn't implant extra anterior pituitary glands. To confirm that prolactin itself was responsible for the effects they saw in the overproducers, the researchers injected some of the rats that had the real surgery with a drug that deactivated extra prolactin, bringing the overproducers' prolactin down to baseline levels.

As a contrast to these prolactin overproducers, the researchers also studied mice that were genetically engineered to not have prolactin receptors. Thus, even though these mice made prolactin, their bodies behaved as if they had none of the hormone because their cells couldn't process it.

The researchers measured the ratio of liver to body weight in each of the rats and mice. They tested how readily liver and liver blood vessel cells were dividing in some of the animals from each group. They also removed portions of the animals' livers, comparing how quickly animals from each group regenerated liver tissue. Additionally, they tested the animals' levels of interleukin-6 (IL-6), a chemical produced by cells and is kept in check by prolactin. IL-6 can stimulate the liver to repair itself at low levels but can hinder this self-repair at higher levels.

Results

The researchers found that rats that overproduced prolactin had larger livers in proportion to their body weight compared to rats that had normal prolactin levels and those that overproduced prolactin but received the nullifying drug. These overproducers also had significantly larger livers in proportion to their body weight compared to the mice that couldn't process prolactin. Liver cells and liver blood vessel cells were multiplying more readily in the prolactin overproducers than in animals in the other groups.

After the researchers removed portions of the animals' livers, the prolactin overproducers regenerated their livers more quickly than animals from the other groups. Mice that didn't process prolactin not only had smaller livers than the normal mice but were also significantly more likely to die in the days after surgery. Tests showed that these mice had elevated levels of IL-6, a factor that could be partially responsible for their slower healing and increased mortality.

Importance of the Findings

These findings suggest that prolactin is important both for normal liver growth and for regenerating the liver after part of it is removed, with extra prolactin providing a boost for repair mechanisms. Consequently, enhancing prolactin levels could provide a way to improve regeneration when the liver becomes damaged or diseased, or after surgery.

"The use of current medications known to increase prolactinemia (prolactin production) constitute potential therapeutic options in liver diseases, liver injuries, or after liver surgery and warrants further investigation," the study authors write.

Prolactin promotes normal liver growth, survival, and regeneration in rodents: Effects on hepatic IL-6, suppressor of cytokine signaling-3, and angiogenesis . In addition to Carmen Clapp, the study team also includes Bibiana Moreno-Carranza, Maite Goya-Arce, Claudia Vega, Norma Adan, Jakob Triebel, Fernando Lopez-Barrera, and Gonzalo Martinez de la Escalera, of the Universidad Nacional Autonoma de Mexico, Andres Quintanar-Stephano of the Universidad Autonoma de Aguascalientes, and Nadine Binart of Universite Paris-Sud. Am J Physiol Regul Integr Comp Physiol 305:R720-R726, 2013. First published 15 August 2013; doi:10.1152/ajpregu.00282.2013

American Physiological Society

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Human stem cell-derived hepatocytes regenerate liver function

Public release date: 26-Jul-2013
Contact: Vicki Cohn
vcohn@liebertpub.com
914-740-2100 x2156
Mary Ann Liebert, Inc./Genetic Engineering News

And extend survival in mice with hepatic failure

New Rochelle, NY, July 26, 2013 -- Researchers have generated functional hepatocytes from human stem cells, transplanted them into mice with acute liver injury, and shown the ability of these stem-cell derived human liver cells to function normally and increase survival of the treated animals. This promising advance in the development of cell-based therapies to treat liver failure resulting from injury or disease relied on the development of scalable, reproducible methods to produce stem cell-derived hepatocytes in bioreactors, as described in an article in Stem Cells and Development, a peer-reviewed journal from Mary Ann Liebert, Inc., publishers. The article is available free on the Stem Cells and Development website.

Massoud Vosough and coauthors demonstrate a large-scale, integrated manufacturing strategy for generating functional hepatocytes in a single suspension culture grown in a scalable stirred bioreactor. In the article "Generation of Functional Hepatocyte-Like Cells from Human Pluripotent Stem Cells in a Scalable Suspension Culture" the authors describe the method used for scale-up, differentiation of the pluripotent stem cells into liver cells, and characterization and purification of the hepatocytes based on their physiological properties and the expression of liver cell biomarkers.

David C. Hay, MRC Centre for Regenerative Medicine, University of Edinburgh, U.K., comments on the importance of Vosough et al.'s contribution to the scientific literature in his editorial in Stem Cells and Development entitled "Rapid and Scalable Human Stem Cell Differentiation: Now in 3D." The researchers "developed a system for mass manufacture of stem cell derived hepatocytes in numbers that would be useful for clinical application," creating possibilities for future "immune matched cell based therapies," says Hay. Such approaches could be used to correct mutated genes in stem cell populations prior to differentiation and transplantation, he adds.

"The elephant in the room for stem cell therapy rarely even acknowledged let alone addressed in the literature is that of scalable production of cells for translational application," says Editor-in-Chief Graham C. Parker, PhD, research professor, Carman and Ann Adams Department of Pediatrics, Wayne State University School of Medicine. "Baharvand's groups' landmark publication not only demonstrates but exquisitely describes the methodology required to scale up stem cell populations for clinical application with a rigor to satisfy necessary manufacturing standards."

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About the Journal

Stem Cells and Development is an authoritative peer-reviewed journal published 24 times per year in print and online. The Journal is dedicated to communication and objective analysis of developments in the biology, characteristics, and therapeutic utility of stem cells, especially those of the hematopoietic system. Complete tables of content and a free sample issue may be viewed on the Stem Cells and Development website.

About the Publisher

Mary Ann Liebert, Inc., publishers is a privately held, fully integrated media company known for establishing authoritative peer-reviewed journals in many promising areas of science and biomedical research, including Cellular Reprogramming, Tissue Engineering, and Human Gene Therapy. Its biotechnology trade magazine, Genetic Engineering & Biotechnology News (GEN), was the first in its field and is today the industry's most widely read publication worldwide. A complete list of the firm's 70 journals, books, and newsmagazines is available on the Mary Ann Liebert, Inc., publishers website.

Mary Ann Liebert, Inc. 140 Huguenot St., New Rochelle, NY 10801-5215 Phone: (914) 740-2100 (800) M-LIEBERT Fax: (914) 740-2101 http://www.liebertpub.com

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New Liver Cell for Cellular Therapy to Aid in Liver Regeneration

Provided by ScienceDaily

June 6, 2013 — Liver transplantation is the mainstay of treatment for patients with end-stage liver disease, the 12th leading cause of death in the United States, but new research from the Icahn School of Medicine at Mount Sinai, published in the journal Cell Stem Cell today, suggests that it may one day become possible to regenerate a liver using cell therapy in patients with liver disease. Investigators discovered that a human embryonic stem cell can be differentiated into a previously unknown liver progenitor cell, an early offspring of a stem cell, and produce mature and functional liver cells.

"The discovery of the novel progenitor represents a fundamental advance in this field and potentially to the liver regeneration field using cell therapy," said the study's senior author, Valerie Gouon-Evans, PharmD, PhD, Assistant Professor, in the Department of Developmental and Regenerative Biology, Black Family Stem Cell Institute, at the Icahn School of Medicine at Mount Sinai. "Until now, liver transplantation has been the most successful treatment for people with liver failure, but we have a drastic shortage of organs. This discovery may help circumvent that problem."

In conjunction with the laboratory of Matthew J. Evans, PhD, from the Department of Microbiology at Icahn School of Medicine at Mount Sinai, investigators demonstrated the functionality of the liver cells generated from the progenitors, as the liver cells can be infected by the hepatitis C virus, a property restricted to liver cells exclusively.

A critical discovery in this research was finding that the novel progenitor has a receptor protein on its cell surface called KDR, or vascular endothelial growth factor receptor 2, which until now, was thought to be restricted to endothelial cells that form vessels, the progenitors for endothelial cells and the progenitors blood cells. The research team showed that activation of KDR on these novel liver progenitors differentiates them into mature liver cells. Additionally, work in a mouse model revealed similar cells, indicating that the progenitors are conserved from mouse to human, and therefore, they must be "important cells with promising potential for cell therapy in treating liver disease," explained Dr. Gouon-Evans.

Next, the research team will examine specifically whether these liver cells obtained from human embryonic stem cells in a dish help repair injured livers in preclinical animal models of liver disease.

Funding for this study was provided by The Black Family Stem Cell Institute, the National Institute of Diabetes and Digestive and Kidney Diseases, the Robin Chemers Neustein Postdoctoral Fellowship, the American Cancer Society, and Pew Charitable Funds.

About The Black Family Stem Cell Institute The Black Family Stem Cell Institute is Mount Sinai's foundation for both basic and disease-oriented research on embryonic and adult stem cells. The therapeutic use of stem cells is a promising area of medicine for the decades ahead and researchers are examining why stem cells function in certain types of niches, microenvironments, and pockets of activity. Investigators are working to break the code in stem cell communication by determining how stem cells signal one another and other cells. The new knowledge that will result from this research holds the promise of diagnostic and therapeutic breakthroughs.

Studies show that it is possible to reprogram adult skin cells into cells that are very similar to embryonic stem cells. Once stem cells can be grown and differentiated in a controlled way to replace degenerated cells and repair tissues, medical science may then be able to diagnose and cure many intractable diseases at their earliest stages, such as type 1 diabetes, Parkinson's disease, various cardiovascular diseases, liver disease, and cancer.

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Story Source:

The above story is reprinted from materials provided by The Mount Sinai Hospital / Mount Sinai School of Medicine, via Newswise.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

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Journal Reference:

1. Orit Goldman, Songyan Han, Marion Sourrisseau, Noelle Dziedzic, Wissam Hamou, Barbara Corneo, Sunita D’Souza, Thomas Sato, Darrell N. Kotton, Karl-Dimiter Bissig, Tamara Kalir, Adam Jacobs, Todd Evans, Matthew J. Evans, Valerie Gouon-Evans. KDR Identifies a Conserved Human and Murine Hepatic Progenitor and Instructs Early Liver Development. Cell Stem Cell, 2013; 12 (6): 748 DOI: 10.1016/j.stem.2013.04.026

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Scarring Cells Revert To Inactive State As Liver Heals

UC San Diego School of Medicine

A photomicrograph of cirrhotic liver tissue, with extensive fibrotic scarring (stained blue).

Released:5/7/2012 3:40 PM EDT
Source:University of California, San Diego Health Sciences

Research with mice reveals possible strategy to reverse fibrosis in liver and other organs

Newswise — An international team of scientists, led by researchers at the University of California, San Diego School of Medicine, report that significant numbers of myofibroblasts – cells that produce the fibrous scarring in chronic liver injury – revert to an inactive phenotype as the liver heals. The discovery in mouse models could ultimately help lead to new human therapies for reversing fibrosis in the liver, and in other organs like the lungs and kidneys.

The work is published in the May 7, 2012 online Early Edition of the Proceedings of the National Academy of Sciences.

“The take-away message is two-fold,” said David A. Brenner, MD, vice chancellor for Health Sciences, dean of the UC San Diego School of Medicine and senior author of the paper. “First, we’ve shown that liver fibrosis is markedly reversible and we now better understand how it happens. Second, we can start looking for ways to direct active myofibroblasts to stop producing scar, and become inactive. We can focus on developing drugs that promote cell change and regression. It raises the bar for prospective treatment tremendously.”

Liver fibrosis is the 12th leading cause of death in the United States. It is the result of chronic liver injury caused by such agents as the hepatitis B and C viruses, alcoholic liver disease and non-alcoholic steatohepatitis. The condition is manifested by extensive scarring of liver tissue and the organ’s progressive inability to filter body toxins. Liver fibrosis precedes the development of liver cancer. Often, the only treatment for end-stage liver fibrosis is an organ transplant.

Fibrosis begins when infectious agents or excessive alcohol consumption trigger activation of hepatic stellate cells (HSCs), which normally act as quiescent storage units for nutrients like vitamin A in the liver. Once activated, these HSCs acquire characteristics of another cell type called myofibroblasts, which are characterized by their abundant production of extracellular matrix proteins such as collagen. These proteins accumulate as scar tissue, rendering the organ progressively dysfunctional.

However, if the source of the liver injury is successfully treated or eliminated, the liver can repair itself. In part, this is due to the activated HSCs undergoing apoptosis (programmed cell death) and being removed by other cells. But UC San Diego scientists say that, in tests using a mouse model, as many as half of all activated HSCs persist. They do not die, but rather revert to an inactive phenotype during fibrotic regression.

“After one month of regression, these cells have stopped producing collagen. They’ve upregulated some of the genes associated with quiescence and returned to their normal location in the liver,” said Tatiana Kisseleva, MD, PhD, an assistant research scientist and first author of the study.

It’s not clear why these myofibroblasts survive. Also, scientists note the reverted myofibroblasts do not completely return to their original quiescent state. “They’re still more susceptible to repetitive injury than original quiescent HSCs,” said Kisseleva, who noted future tests will investigate whether additional reversion occurs with more time.

Kisseleva suggested the findings present another avenue for treating liver fibrosis, especially in possibly reverting fibrosis and cirrhosis, which accounts for roughly 27,000 deaths in the United States annually.

Fibrosis occurs in other organs as well, such as the kidneys and lungs, with comparable deadly effect. Recent studies indicate fibrotic reversibility in these organs as well. “Our findings are applicable to other fibrosing organs,” said Kisseleva. “Instead of killing damaged cells, we might be able to de-activate them and revert them to healthy originals.”

Co-authors of the study are Min Cong, Chunyan Jiang, Keiko Iwaisako, Brian Scott and Wolfgang Dillmann, Department of Medicine, UC San Diego; YongHan Paik, Department of Medicine, UC San Diego and Department of Medicine, Sungkyunkwan University School of Medicine, Seoul, South Korea; David Scholten, Department of Medicine, UC San Diego and Department of Medicine III, University Hospital Aachen, Germany; Thomas Moore-Morris and Sylvia M. Evans, Skaggs School of Pharmacy and Pharmaceutical Science, UC San Diego; Hidekazu Tsukamoto, Keck School of Medicine, University of Southern California.

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EASL 2012: Gallbladder shown as potential stem cell source for regenerative liver and metabolic disease

Posted On: April 19, 2012 - 9:31am

A new study presented today at the International Liver Congress™ 2012 indicates the potential for gallbladder tissue (which is routinely discarded from organ donors and surgical interventions) to be a highly available candidate source for multipotential stem cells.(1)

Biliary tree stem/progenitor cells (BTSCs) have previously been identified in the glands of normal adult human extrahepatic bile ducts and been shown to generate in vitro and in vivo mature cells of the hepato-biliary and pancreatic endocrine lineages.

The study found both normal and pathological gallbladders contained easily isolable cells with the phenotype and biological properties of BTSCs. Interestingly, in an animal model, these cells were able to repopulate the injured liver and to improve synthetic functions.

These data open novel perspectives for the collection and use of multipotent stem cells in regenerative therapies of liver, bile duct, and pancreatic diseases including diabetes

Source: European Association for the Study of the Liver

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Turning Lymph Nodes Into Liver-Growing Factories

If your liver fails, having 40 small but functional livers scattered around your body might be the next best thing.

by Adam Piore

From the March 2012 issue; published online April 11, 2012

For people suffering from advanced liver disease, the prognosis is bleak. In many patients, such as those with cirrhosis, the liver becomes so clogged with scar tissue that healthy cells are choked off, preventing it from fulfilling its role of filtering toxins. The only cure is a liver transplant. Yet with just 6,000 available organs for some 100,000 patients each year, chances of winning the liver lottery are slim. And if you’re elderly or suffering from another disease, the chances are closer to zero.

But a surprising new technique under development by University of Pittsburgh stem cell researcher Eric Lagasse may radically improve those odds. Lagasse, based at Pitt’s McGowan Institute for Regenerative Medicine, has discovered how to turn any one of the body’s 500 lymph nodes—the small, oval-shaped organs where immune cells gather to fight invading pathogens—into an incubator that can grow an entirely new liver. Creating a whole set of miniature new livers might take as little as obtaining liver cells from healthy donors and placing them inside the lymph nodes of patients suffering from liver disease.

The concept was born in 2007, while Lagasse was pondering how to overcome a major roadblock to liver regeneration—in those with liver disease, the organ forms scar tissue that destroys its ability to heal. But then he noticed emerging evidence that transplanted liver cells could survive in unusual areas of the body, for instance under the renal capsule, a fibrous layer that protects the kidney from trauma. Lagasse reasoned that if he could implant liver cells away from the diseased organ, instead of succumbing they just might multiply and thrive.

So he set to work trying to grow liver cells outside the dying organ. As his test tube, he used mice with end-stage liver disease, implanting liver cells, or hepatocytes, from another mouse into their kidney capsules, under the skin, and into the spleen. Most of the mice died within eight weeks, the usual prognosis for end-stage liver failure in mice. But that changed when Lagasse injected cells into the belly: The mice gained weight, recovered energy, and within weeks appeared healthy.

After watching those mice thrive for several months, Lagasse repeated the experiment using fluorescent markers to trace the path of the liver cells. To his surprise, they had migrated to lymph nodes, where they grew to form large nodules that, in aggregate, reached a mass capable of keeping the animal alive.

It actually made sense. In many ways, lymph nodes are ideal bioreactors for growing new livers. They have an unusual capacity to expand, allowing them to accommodate an entire organ. They have ready access to the bloodstream, which nurtures new cells with nutrients as well as hormones and signaling agents needed for growth. And since the body has many lymph nodes, some can sacrifice their traditional duties to grow livers. The injections were so successful, Lagasse realized, because the belly provided enough space for cells to migrate.

Further experimentation showed Lagasse that if he injected hepatocytes directly into the lymph nodes, the cells picked up signaling proteins (essentially SOS signals to grow) released into the bloodstream from the dying liver. “There is communication between the new and a diseased liver,” Lagasse says. “They share some functions. We don’t totally understand the signaling mechanism, but we don’t need to if it works.”

Using his technique in mice, Lagasse has already succeeded in growing 20 to 40 small livers that gradually pick up the slack as the central liver fades. Together the mini-livers add up to 70 percent the size of a normal liver.

So far, Lagasse has not seen adverse reactions in his experimental mice. Rejection is not a problem because the animals were genetically engineered to share identical DNA, eliminating the risk that the immune system would attack foreign hepatocytes. In humans, Lagasse is banking on immunosuppressant drugs to prevent rejection. Further ahead, he is looking to an emerging technology known as induced pluripotent stem cells (iPSCs), in which adult cells are reprogrammed to be like embryonic stem cells so they can transform into any type of cell. Doctors could then collect blood or skin cells from a patient and turn them into healthy liver cells, enabling patients to be their own donors.

Even if rejection can be controlled, patients gravely ill from end-stage liver disease might succumb to surgery itself. To address this, Lagasse has injected hepatocytes into lymph nodes in peripheral parts of a mouse’s body—under the knee or arm—because that requires less invasive surgery. Growing a liver behind a knee is not ideal; in humans it might cause a bump weighing more than a pound in an inconvenient spot. But cultivating a liver in these peripheral areas could allow a very sick patient to survive long enough to recover the strength to undergo implantation in a more practical location.

Next Lagasse plans to replicate his experiments in pigs and hopes to implant human patients within the next few years. In principle, there’s no reason the approach should be limited to livers. “We’re talking about bioreactors that could grow any number of tissues inside the body,” Lagasse says. “This could work for any organ that secretes things or produces cells.” The thymus and pancreatic cells may be future candidates.

Stem cell expert Robert Lanza, who heads scientific research at Advanced Cell Technology in Massachusetts, calls the research an “exciting, novel idea.” But he sounds notes of caution. Liver cells carry out hundreds of different functions, only some of which Lagasse has tested in mice, and it is unlikely that transplanted cells could fulfill all of them in humans. “Also, you can envision all sorts of locations where it would not be good to have these cells,” he says. “What if they migrate to the lungs or brain?”

Lagasse concedes the many hurdles that lie ahead, not the least of which is convincing people that his bizarre transplantation technique might work. “This is such a wild idea, we need to demonstrate it could actually be used on a patient,” Lagasse says. “Still, I’ve spoken to many surgeons who are very excited about it.”

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Breakthrough could lead to cure for chronic liver disease

By Steve Connor

Monday March 05 2012

MEDICAL scientists have taken an important step towards understanding how the diseased liver can repair itself in a breakthrough that could eventually lead to the development of new treatments for chronic liver illnesses, which at present can only be cured by organ transplants.

The researchers have worked out how to stimulate the production of vital liver cells known as hepatocytes which are lost when the liver is attacked by potentially fatal conditions such as cirrhosis or chronic hepatitis.

Liver disease is the fifth biggest killer in Britain and is the only major cause of death that has seen a continual year-on-year increase over the past 40 years – more than twice as many people die of liver disease now compared with 20 years ago.

About 16,000 people in the UK died last year of liver disease, and the number of people on the waiting list for organ transplants has increased from about 300 five years ago to nearly 500 now.

The latest research, published in the journal Nature Medicine, has unravelled the network of complex biochemical signals that trigger the regeneration of cells within the liver, the body's main organ for filtering harmful toxins from the bloodstream.

Although the human liver has remarkable powers of natural regeneration, this often results in the replacement of the wrong kind of liver cells. Instead of hepatocytes, the damaged liver tends to make to many bile duct cells, the scientists said.

The scientists were able to shift the balance towards making more hepatocytes by altering the expression of certain genes at the earliest stages of liver cell development. The discovery could lead to the development of drugs that perform the same function in patients, they said.

Luke Boulter of the Medical Research Council's Centre for Regenerative Medicine at Edinburgh University, and lead author of the study, said that understanding how new liver cells are regenerated is key to finding ways of repairing damaged liver tissue.

"This research helps us to know how to increase numbers of cells that are needed for healthy liver function and could pave the way to finding drugs that help liver repair," Dr Boulter said.

Professor Stuart Forbes, associate director of the Centre for Regenerative Medicine, said such studies are needed to tackle the increase in demand for liver transplants. "But the supply of donated organs is not keeping pace with the demand. If we can find ways to encourage the liver to heal itself then we could ease the pressure on waiting lists."

- Steve Connor

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Boosting cell production could help treat liver disease

Public release date: 4-Mar-2012

Contact: Catriona Kelly
Catriona.Kelly@ed.ac.uk
44-131-651-4401
University of Edinburgh

Scientists have shed light on how the liver repairs itself with research that could help develop drugs to treat liver disease

Scientists have shed light on how the liver repairs itself with research that could help develop drugs to treat liver disease.

Researchers at the Medical Research Council (MRC) Centre for Regenerative Medicine at the University of Edinburgh have discovered how to enhance the production of key cells needed to repair damaged liver tissue.

The study, published in the journal Nature Medicine, could help heal livers affected by diseases such as cirrhosis or chronic hepatitis.

Scientists were able to unpick the process of how different cells in the liver are formed.

When the liver is damaged it produces too many bile duct cells and not enough cells called hepatocytes, which the liver needs to repair damaged tissue.

They found they could increase the number of hepatocyte cells – which detoxify the liver – by encouraging these cells to be produced instead of bile duct cells.

Understanding how liver cells are formed could help to develop drugs to encourage the production of hepatocytes to repair liver tissue. This could eventually ease the pressure on waiting lists for liver transplants.

Professor Stuart Forbes, Associate Director at the MRC Centre for Regenerative Medicine at the University of Edinburgh, who is a consultant hepatologist and was the academic leader of the study, said: "Liver disease is on the increase in the UK and is one of the top five killers. Increasing numbers of patients are in need of liver transplants, but the supply of donated organs is not keeping pace with the demand. If we can find ways to encourage the liver to heal itself then we could ease the pressure on waiting lists for liver transplants."

Liver disease is the fifth biggest killer in the UK. There are almost 500 people waiting for a liver transplant, compared to just over 300 five years ago.

The production of hepatocyte cells was increased by altering the expression of certain genes in early stage liver cells.

Dr Luke Boulter, of the University of Edinburgh's MRC Centre for Regenerative Medicine and first author on the paper, said: "This research helps us know how to increase numbers of cells that are needed for healthy liver function and could pave the way for finding drugs that help liver repair. Understanding the process in which cells in the liver are formed is key in looking at ways to repair damaged liver tissue."

Dr Rob Buckle, Head of Regenerative Medicine at the MRC, said: "Liver transplants have saved countless lives over the years, but demand will inevitably outstrip supply and in the long term we need to look beyond replacing damaged tissues to exploiting the regenerative potential of the human body. The MRC continues to invest heavily across the breadth of approaches that might deliver the promise of regenerative medicine, and this study opens up the possibility of applying our increasing knowledge of stem cell biology to stimulate the body's own dormant repair processes as a basis for future therapy."

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The study was carried out in collaboration with the University's MRC Centre for Inflammation Research, the Beatson Institute for Cancer Research in Glasgow and the K.U. Leuven in Belgium.

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Research could solve donor liver shortage

16/12/2011 03:49:00

Research from Curtin University could see bio-engineered liver tissue used instead of donor tissue for liver transplants.

The research aims to address the increasing burden of liver disease and shortage of donor organs occurring in all Western countries.

Dr Nina Tirnitz-Parker, research fellow at Curtin’s School of Biomedical Sciences, has spent the past eight years developing a method of bio-engineering liver cells, or hepatocytes, to replace tissue lost to disease or injury.

“More and more people die while on the waiting list for donor livers,” Dr Tirnitz-Parker said.

“So there’s an urgent need to develop new treatments for liver diseases and avoid the need of a liver transplant.”

Her research is based on the liver’s ability to restore itself with stem cell-like liver progenitor cells (LPCs) in chronic liver injury conditions such as alcoholic liver disease or hepatitis C virus infection.

LPCs contribute to liver regeneration by moving to injury sites where there is a loss of functional liver mass, and then differentiating into required hepatocytes and bile duct cells.

However, there are good and bad aspects to LPCs.

“LPCs interact with cells that drive scarring of the liver, which is known as liver fibrosis,” Dr Tirnitz-Parker said.

“We need to understand how we make these cells secrete the right signals that prevent fibrosis from occurring, which may in turn stop the onset of liver cirrhosis and liver cancer.”

Dr Tirnitz-Parker’s ongoing investigations include the role of LPCs in hepatitis C patients after liver transplantation, and the relationship of LPCs to cancer stem cells.

“Our research aims are twofold. Firstly, we want to develop a safe method of liver tissue engineering using LPCs and secondly, we would like to understand the role of LPCs in the carcinogenic pathway, including how to regulate their growth and prevent tumours developing,” Dr Tirnitz-Parker said.

Dr Tirnitz-Parker is working closely with Professor John Olynyk, a renowned clinical gastroenterologist at Fremantle Hospital and deputy director of the Western Australian Institute for Medical Research (WAIMR), and Professor George Yeoh, Head of WAIMR’s laboratory for Liver Disease and Carcinogenesis.

The research into the therapeutic potential of LPCs is progressing from the WAIMR team’s discovery that a protein known as TWEAK stimulates the growth of LPCs.

In addition to Professor Olynyk, who is also an Adjunct Professor within the Curtin Health Innovation Research Institute (CHIRI), the research collaboration includes researchers from the University of Western Australia, the Queensland Institute of Medical Research, the University of Sydney and Loma Linda University, in California.

As part of this work Dr Tirnitz-Parker, Professor Olynyk and Associate Professor Grant Ramm from the Queensland Institute for Medical Research were also recently awarded $600,000 in nationally competitive research funding from the National Health and Medical Research Council Australia to investigate “The Role Of Hepatic Stellate Cell And Liver Progenitor Cell Interactions In The Regulation Of Wound Healing And Liver Regeneration”

Contact:

Dr Nina Tirnitz-Parker, Research Fellow, School of Biomedical Sciences, Curtin University

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Liver Regeneration Boosted by Blocking Cell-Specific Serotonin Receptor

GEN News Highlights: Nov 28, 2011

Blocking activity of the 5-HT_2B serotonin receptor on fibrogenic hepatic stellate cells (HSCs) in the liver may provide a new approach to boosting liver regeneration in injury and disease, scientists suggest. They report on research demonstrating that scar-causing hepatic stellate cells (HSCs) in the liver are negative regulators of hepatocyte regeneration, and that this negative regulatory activity requires stimulation of the 5-hydroxytryptamine 2B receptor (5-HT_2B) on HSCs by serotonin.

The studies, which were led by the Newcastle University’s Institute of Cellular Medicine, showed that selective antagonism of 5-HT_2B on HSCs enhanced hepatocyte growth in rodent models of acute and chronic liver injury. Similar effects were also seen in mice lacking 5-HT_2B. The findings are reported in Nature Medicine in a paper titled “Stimulating healthy tissue regeneration by targeting the 5-HT_2B receptor in chronic liver disease.”

Liver disease is characterized by reduced hepatocyte regeneration, which is accompanied by fibrogenesis and the development of liver cirrhosis and cancer, the authors explain. Unfortunately, the complexity of pathways that regulate hepatocyte proliferation, including the contribution of fibrogenic HSCs, is not well understood.

What has been shown, however, is that in the diseased liver HSCs transdifferentiate into activated myofibroblasts that drive fibrogenesis and secrete soluble factors such as hepatocyte growth factor, TGF-β1, and interleukin-6 (IL-6), which might impact on hepatocyte proliferation.

To investigate the role of HSCs in hepatocyte regeneration the team first evaluated the effects of triggering selective apoptosis-mediated depletion of HSCs on hepatocyte proliferation in bile duct-ligated (BDL) mice, a well-established rodent model of extrahepatic cholestasis. To effect selective apoptosis, HSCs were targeted using a single-chain antibody, C1-3, conjugated to gliotoxin. This mycotoxin is specific to synaptophysin, an antigen expressed on myofibroblasts positive for α-smooth muscle actin (α-SMA+ myofibroblasts), which are specifically derived from the transdifferentation of HSCs.

Treatment of BDL mice using C1–3 gliotoxin resulted in marked but not complete, deletion of hepatic α-SMA+ cells in mice ( α-SMA+ myofibroblasts derived from other cell types weren’t affected) and the stimulation of hepatocyte proliferation. Importantly, there was no accompanying change in the expression of the hedgehog target gene Gli2, which indicated that stimulation of hepatocyte growth after HSC depletion wasn’t due to activation of the hedgehog pathway, the authors note.

The team’s previous work had identified functional 5-HT_2B serotonin receptors on activated HSCs in liver disease. Hence, they next looked at whether paracrine signaling between HSCs and hepatocytes might explain the antiregenerative properties of HSCs. To investigate the influence of 5-HT_2B on hepatocyte regeneration during liver injury the researchers used a drug called SB-204741, which is a highly specific 5-HT_2B antagonist but has negligible effects on the 5-HT_2A and 5-HT_2C receptor subtypes.

Studies in the experimental mice showed that administration of SB-204741 stimulated hepatocyte proliferation in progressive BDL-induced liver injury and in liver damage induced by acute carbon tetrachloride (CCl₄) administration. These results indicated a specific antiregenerative role for 5-HT_2B signal, a notion supported by studies in 5-HT_2B knockout mice (Htr2b^-/-).

Partial hepatectomy (PHX) in these knockout animals led to elevated hepatocyte proliferation. Levels of IL-6 and TNF-α, which are primers of hepatocyte regeneration and expressed transiently shortly after surgery, were modestly increased in 5-HT_2B knockout mice at four hours of PHX. Crucially, though, the production of TGF-β1, which is induced in the end stage of liver regeneration and acts to repress hepatocyte proliferation, was evident in the livers of wild-type mice at 36 hours after PHX but not in the livers of 5-HT_2B knockout animals.

Interestingly, the investigators report, the liver-to-bodyweight ratios of wild-type mice treated using SB-204741 increased after PHX, indicating that selective antagonism of 5-HT_2B results in sustained stimulation of liver regeneration.

5-HT_2B is expressed on HSCs in diseased liver but at lower levels on cholangiocytes and Kupffer cells, the researchers continue. Studies indicated that 5-HT_2B was induced in HSCs after PHX, but its expression was reduced in hepatocytes. Treatment with C1-3-gliotoxin increased hepatocyte proliferation after PHX, and this was associated with reduced hepatic expression of TGF-β1.

Thus far, it appeared that HSC depletion and 5-HT_2B antagonism had similar effects on hepatocyte proliferation in models of liver damage, but what wasn’t known was whether they acted through independent mechanisms. If so, then additive effects should be observed when combining HSC depletion with 5-HT_2B antagonism. However, while the combination of HSC depletion and SB-204741 treatment in CCl₄-injured mice enhanced hepatocyte proliferation and inhibited TGF-β1 expression, there were no additive effects.

The investigators next designed chromatin immunoprecipitation studies to identify the intracellular signaling pathways through which serotonin and 5-HT_2B exert their antiregenerative effects. They found that either antagonism of 5-HT_2B or treatment using the ERK inhibitor PD98059 suppressed serotonin-induced recruitment of JunD, which is one half of the heterodimer making up the AP-1 transcription factor that controls transcription of TGFβ1. Likewise serotonin-induced phosphorylation of JunD was also suppressed on administration of PD98059 or SB-204741.

“On the basis of these data, we propose that phosphorylation and activation of JunD by ERK mediates the stimulation of TGF-β1 transcription by serotonin and 5-HT_2B in HSCs,” the authors conclude. “If this pathway operates in the context of the injured liver, then JunD would be predicted to function as a transcriptional repressor of hepatocyte proliferation.”

In confirmation of this, the team found that compared with wild-type mice, JunD-knockout mice recovering from CCl₄ injury demonstrated higher numbers of mitotic hepatocytes, which was associated with reduced TGF-β1 expression.

The researchers finally moved on to evaluate whether 5-HT_2B antagonism would have an antifibrogenic effect in mouse models of progressive liver disease in which both fibrogenesis and regeneration result in remodeling of the hepatic architecture. Experimental animals were given CCl₄ injections over three weeks to establish fibrotic disease, and then CCl₄ treatment was continued either with or without treatment with SB-204741.

“Treatment with SB-204741 significantly reduced the number of hepatic α-SMA+ fibrogenic cells, fibrotic matrix, hepatic expression of TGF-β1, and expression of the fibrogenic genes encoding TIMP-1 and pro-collagen I, confirming an antifibrogenic effect at the molecular level,” they write.

Moreover, SB-20741 administration was linked with a higher rate of cellular apoptosis in the fibrotic matrix. Administration of SB-20471 in the model of progressive BDL-induced liver disease also resulted in a protective antifibrotic effect as well as improvements in liver function.

The overall results demonstrate that the negative regulation of hepatocyte regeneration by HSCs in the liver requires stimulation of the 5-HT_2B receptor on HSCs by serotonin, which activates expression of TGF-β1 through signaling by ERK1 and the transcription factor JunD, the authors conclude.

“5-HT_2B is selectively expressed by activated human HSCs and the signaling pathway we describe here is conserved in human HSCs. Potent and selective antagonists of 5-HT_2B are already available and have been reported as being safe for clinical use in humans. This class of drug may therefore have therapeutic potential in liver disease, both as stimulants of hepatocyte regeneration and as anti-fibrotic agents.”

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Adult Stem Cells Treat End-Stage Liver Disease

by David Prentice
January 26, 2011

A team of researchers in California and in Egypt report therapeutic benefit treating end-stage liver disease patients with adult stem cells A total of 48 patients were treated with their own adult stem cells–36 patients with chronic, end-stage hepatitis C-induced liver disease, and 12 patients with end-stage autoimmune liver disease. Researchers used the factor G-CSF, commonly used to mobilize bone marrow adult stem cells into the circulation, to obtain the cells from each patient. The CD34+ stem cells were then isolated, amplified to increase numbers of cells, partially differentiated in culture, then re-injected into each patient via their hepatic artery or portal vein. The results were published in Cell Transplantation

According to co-author Dr. Mark A. Zern of University of California-Davis Medical Center:

“This enabled us to transplant as many as one billion of these cells per patient. For all patients there was a statistically significant decrease in peritoneal cavity fluid, or ‘ascites’. There was also clinical and biochemical improvement in a large percentage of patients who received the transplantation. The finding of improvement in ascites in a significant number of patients is impressive and somewhat surprising, suggesting that cell transplantation might be clinically significant beyond the improvement in laboratory parameters.”

The mechanism by which the infusion of CD34+ adult stem cells improves liver function is still unclear. As to whether any partial differentiation into liver cells was needed for the therapeutic results, Dr. Stephen Strom at the University of Pittsburgh and section editor for Cell Transplantation, noted:

“Other research groups are now showing similar results with cells without any hepatic characteristics, including fractionated and unfractionated bone marrow and mesenchymal stem cells. Taken together, these data suggest that the positive effects these researchers find may be the result of paracrine effects from factors secreted by the donor cells.

Published data in 1999 suggested that some bone marrow adult stem cells could form liver hepatocytes. Others reported similar results in 2000 using mice, by observing liver cells of human bone marrow adult stem cell transplant patients, and in experiments showing regeneration of liver in mice. However, some published evidence also indicates that the regenerative capacity of bone marrow adult stem cells is due to paracrine effects, i.e., secreted factors.

No matter what the mechanism, various clinical trials are investigating use of adult stem cells for liver diseases. Published results from earlier trials show therapeutic benefit of adult stem cells for liver repair and regeneration.

In a published 2010 report, a Korean group found some improvement in liver cirrhosis patients using their own adult stem cells.

In 2006 a U.K. group reported improvement in patients with liver insufficiency treated with their own adult stem cells, and the same group reported in 2008 the long-term improvement of chronic liver disease patients, using the patients’ own adult stem cells in a trial similar to the current Egyptian trial.

Also in 2006, a German group reported increased liver regeneration in liver cancer patients using adult stem cells, and a Japanese team found improved liver function in cirrhosis patients after using the patients’ own bone marrow adult stem cells.

Adult stem cells continue to provide ethical and successful results for patients.

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Cell Transplantation reports a success in treating end-stage liver disease

Public release date: 11-Jan-2011

Contact: David Eve
celltransplantation@gmail.com
Cell Transplantation Center of Excellence for Aging and Brain Repair

Tampa, Fla. (Jan. 10, 2011) – Transplanting their own (autologous) bone marrow-derived stem cells into 48 patients with end-stage liver disease resulted in therapeutic benefit to a high number of the patients, report researchers publishing in the current issue of Cell Transplantation (19:11). Yet, the mechanism by which the infusion of CD34+ stem cells improves liver function remains elusive, they say.

The study, carried out by a team of researchers in California and in Egypt, is now freely available on-line at http://www.ingentaconnect.com/content/cog/ct/

According to the study's corresponding author, Dr. Mark A. Zern of the University of California Davis Medical Center, Sacramento, CA, patients with end-stage liver failure in Egypt have few treatment options but for transplantation. A shortage of donors and cost factors make that strategy unrealistic. Accordingly, this study sought to evaluate the safety and efficacy of transplanting autologous bone marrow-derived CD34+ stem cells in 48 patients, 36 of whom had chronic, end-stage hepatitis C-induced liver disease, and 12 with end-stage autoimmune liver disease.

"For all patients there was a statistically significant decrease in peritoneal cavity fluid, or 'ascites,'" said Dr. Zern. "There was also clinical and biochemical improvement in a large percentage of patients who received the transplantation."

The researchers reported that they obtained "reasonable numbers of CD34+ cells" that were then "amplified and partially differentiated into hepatocyte precursor cells."

"This enabled us to transplant as many as one billion of these cells per patient," explained Dr. Zern. "The finding of improvement in ascites in a significant number of patients is impressive and somewhat surprising, suggesting that cell transplantation might be clinically significant beyond the improvement in laboratory parameters."

They also report using granulocyte-colony stimulating factor (G-CSF) to "mobilize…CD34+ stem cells into peripheral circulation." The researchers anticipated that G-CSF would likely enhance a variety of circulating bone marrow-derived cells, producing growth factors which could "positively affect liver regeneration and perhaps have a positive effect on portal hypertension."

The team also reported that prior to transplantation, the cells were already beginning to develop a hepatocyte phenotype while in culture, suggesting that the cells may have acted as hepatocyte-like cells following engraftment. The researchers plan to compare routes of infusion to determine if peripheral infusion of transplanted cells will be adequate.

"The use of peripheral infusion would dramatically reduce both costs and risks for this cell transplantation, thus making the treatment an even more viable option in Egypt and throughout the world," concluded Dr. Zern.

"It would be very interesting to determine if the differentiation to hepatic precursors was a necessary step for this treatment," said Dr. Stephen Strom, a professor of pathology in the Department of Pathology at the University of Pittsburgh and section editor for Cell Transplantation. "Other research groups are now showing similar results with cells without any hepatic characteristics, including fractionated and unfractionated bone marrow and mesenchymal stem cells. Taken together, these data suggest that the positive effects these researchers find may be the result of paracrine effects from factors secreted by the donor cells. I look forward to reading about the outcome of future studies to determine the optimal route of administration and dose of these cells, as well as more long term follow up."

###

Contact: Dr. Mark A. Zern, UC Davis Medical Center, 4635 Second Ave. Ste. 1001, Sacramento, CA
Tel: (916) 734-8063; Fax: (916) 734-8097
Email: mazern@ucdavis.edu

Citation: Salama, H.; Zekri, A-R..; Zern, M.; Bahnassy, A.; Loutfy, S.; Shalaby, S.; Vigen, C.; Burke, W.; Mostafa, M.; Medhat, E.; Alfi, O.; Huttinger, E. Autologous Hematopoietic Stem Cell Transplantation in 48 Patients With End-Stage Chronic Liver Diseases. Cell Transplant. 19(11):1475-1486; 2010.

The editorial offices for CELL TRANSPLANTATION are at the Center of Excellence for Aging and Brain Repair, College of Medicine, the University of South Florida and the Diabetes Research Institute, University of Miami Miller School of Medicine. Contact, David Eve, PhD. at celltransplantation@gmail.com or Camillo Ricordi, MD at ricordi@miami.edu

News Release by Randolph Fillmore, Florida Science Communications, http://www.sciencescribe.net/

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EHSI Secures Rights to Use NASA Developed Stem Cell Technology in China

December 30, 2010 09:12 AM Eastern Time

NASA Developed Bioreactor Could be Huge Boost for Company’s Celulas Genetica Subsidiary

HOUSTON--(BUSINESS WIRE)--Emerging Healthcare Solutions, Inc. (PinkSheets:EHSI) revealed today that their new License Agreement with Regenetech specifically allows the Company to use NASA’s Intrifuge Rotary Cell Culture System in The People’s Republic of China. EHSI has been granted a sub-license for the NASA Intrifuge Rotary Cell Culture System from Regenetech in the License Agreement. What differentiates the NASA technology is the addition of simulated weightlessness in the Rotary Cell Culture System or “bioreactor”. Cell cultures, including stem cells, grown inside the bioreactor look and function much closer to human cells grown within the body than cell cultures grown in Petri dishes. EHSI has also purchased an Intrifuge Rotary Cell Culture System.

This new license is essential to new stem cell research planned by Celulas Genetica, EHSI’s biotech division, including its current endeavor to develop a revolutionary new cure for liver disease known as the Rutherford Procedure. Celulas Genetica is currently planning to test this new procedure in China.

The Rutherford Procedure is a groundbreaking organ regeneration treatment that utilizes proton-beam technology to destroy diseased organ tissue for regeneration using adult stem cells. During the procedure, proton therapy will be used to destroy scar-tissue cells in the liver using high-energy proton beams, a non-invasive treatment proven to minimize damage to healthy tissues and to eliminate the side effects (including nausea) of traditional radiation therapy. As the scar tissue is systematically destroyed by the proton therapy, a catheter will deliver the patient’s own cultured stem cells directly to the patient’s liver through the bloodstream. As more and more diseased tissue is destroyed, these cultured stem cells could help regenerate the patient’s damaged, cirrhotic liver into a healthy, functioning organ once more.

Celulas Genetica purchased a license to develop and market the Rutherford Procedure earlier this month, a day before EHSI announced the company’s acquisition. Celulas Genetica is only the latest outpost in Emerging Healthcare Solutions’ global footprint. In addition to its Houston headquarters, the company also maintains business offices in Frankfurt, Germany and Warsaw, Poland.

See more about Celulas Genetica at: http://www.thestemcellgroup.com/

EHSI invests in technology developed to compete in the medical research industry alongside Amyris Inc. (NASDAQ:AMRS), Quest Diagnostics Inc. (NYSE:DGX), Laboratory Corporation of America (NYSE:LH) and Amgen (NASDAQ:AMGN).

About Emerging Healthcare Solutions, Inc.

Emerging Healthcare Solutions, Inc. invests in and participates in the profits of emerging breakthrough medical technologies. The Company believes the secret of leveraging future value for its shareholders is the proper timing of its investment in promising new medical technologies. EHSI aims to capture future profits of promising new medical technologies by investing in these technologies at the inflection point of product development. We believe this model will deliver long-term positive results for our investors.

For more information about EHSI, please visit http://www.emerginghealthcaresolutionsinc.com/.

Safe Harbor Statement under the Private Securities Litigation Reform Act of 1995: This news release contains forward-looking information within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, including statements that include the words "believes," "expects," "anticipate" or similar expressions. Such forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause the actual results, performance or achievements of the company to differ materially from those expressed or implied by such forward-looking statements. In addition, description of anyone's past success, either financial or strategic, is no guarantee of future success. This news release speaks as of the date first set forth above and the company assumes no responsibility to update the information included herein for events occurring after the date hereof.

Contacts
Emerging Healthcare Solutions, Inc.
Cindy Morrissey, 713-821-1486
President and CEO

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Specialized Blood Vessels Jumpstart and Sustain Liver Regeneration

ScienceDaily (Nov. 11, 2010) — The liver's unique ability among organs to regenerate itself has been little understood. Now Weill Cornell Medical College scientists have shed light on how the liver restores itself by demonstrating that endothelial cells -- the cells that form the lining of blood vessels -- play a key role.

The results of their study are published Nov. 10 in the online edition of the journal Nature, with a companion study in the Oct. 24 issue of Nature Cell Biology describing how endothelial cells are activated to initiate organ regeneration.

It has long been known that endothelial cells passively conduct blood, passing oxygen, nutrients and metabolic waste to and from tissues through capillary walls. However, in studies published in recent years, the Weill Cornell researchers have demonstrated that endothelial cells actively influence the self-renewal of certain stem cell populations and the regeneration of tissue. Now, these scientists have uncovered the endothelial cells' "instructive role" in liver regeneration. Further, the researchers believe that in the coming years it will be possible to facilitate healing damaged livers by transplanting certain types of endothelial cells with liver cells.

"We have found that specialized blood vessel cells in the liver -- a specific type of sinusoidal endothelial cell -- initiate and sustain liver regeneration by producing growth factors that we have identified. This finding will open the door for designing new therapies to treat damaged livers," says the study's senior author, Dr. Shahin Rafii, who is the Arthur B. Belfer Professor in Genetic Medicine and co-director of the Ansary Stem Cell Institute at Weill Cornell Medical College and a Howard Hughes Medical Institute investigator.

The liver performs many physiological functions, including converting nutrients into essential blood components; storing vitamins and minerals; producing bile for digesting fats; regulating blood clotting; and metabolizing and detoxifying substances that would otherwise be harmful. When the liver malfunctions, the consequences can be grave. Liver failure, due to cirrhosis, various forms of hepatitis, and other diseases, kills some 60,000 Americans per year. But the liver's capacity for regeneration is amazing.

"Until our study, the molecular and cellular pathways that would initiate and maintain liver regeneration were not known," says Dr. Bi-Sen Ding, the study's first author and a senior postdoctoral fellow in Dr. Rafii's lab. "Attempts to transplant hepatocytes [liver cells] directly into the liver led to very limited success. But now we have identified liver sinusoidal endothelial cells (LSECs) -- that, when activated, are critical to liver regeneration and may enable proper engraftment when hepatocytes are implanted into the injured liver."

Dr. Rafii's team determined the mechanism by which LSECs regulate liver regeneration by studying this process in genetically engineered mice whose livers were 70 percent removed. Through a series of experiments involving strategic endothelial cell implantation, the team found that only those LSECs whose genes were producing the angiocrine growth factors Id1 or Wnt2 and "hepatocyte growth factor" (HGF) would initiate and sustain liver regeneration. It is thought that Wnt2 and HGF work together in initiating regeneration, and that the LSECs and the liver cells must be next to each other for successful regeneration were key findings.

"Therefore, to regenerate a long-lasting liver, we may need to co-transplant hepatocytes with the properly activated endothelium, which produces the right growth factors for the hepatocytes to attach, grow and connect with other parts of the liver. Co-transplantation of primed activated endothelium with liver cells may be an important step to design future therapies to regenerate the liver," says Dr. Ding.

Despite these new insights, Dr. Rafii points to an unsolved enigma: How do endothelial cells sense the loss of liver tissue and initiate the regeneration process? "Change of blood flow might be one of the possibilities," suggests Dr. Sina Rabbany, study co-senior author, who is an adjunct professor at Weill Cornell and professor of bioengineering at Hofstra University. "It is well known that endothelial cells can sense subtle changes in the flow of blood because they are located at the interface between the blood flow and vessel wall. The loss of a liver lobe will inevitably alter the local blood flow patterns and resulting shear stresses that are redirected into the remaining lobes. This alteration in the biomechanical transduction process is part of a complex system likely to 'activate' endothelial cells to produce hepatocyte-active growth factors."

Dr. David Lyden, a co-author on the paper and the Stavros Niarchos Associate Professor in Pediatric Cardiology at Weill Cornell Medical College, says, "This is an important study. By targeting endothelial-specific genes such as Id1, as identified in this research, I hope that it will facilitate the design of new therapies to treat people with liver disease, whether due to infection, cancer, or acute or long-term damage."

Earlier this year, Rafii's team developed a new technique and described a novel mechanism for turning human embryonic and pluripotent stem cells into plentiful, functional endothelial cells, which are critical to the formation of blood vessels. The new approach allows scientists to generate virtually unlimited quantities of durable endothelial cells -- more than 40-fold the quantity possible with previous approaches. "These embryonic-derived endothelial cells may provide a useful platform to expand liver and blood stem cells for therapeutic transplantation," states Dr. Zev Rosenwaks, who is a co-author in this study and director and physician-in-chief of the Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, as well as the director of the Tri-Institutional Stem Cell Initiative Derivation Unit at Weill Cornell Medical College.

"One of the most remarkable findings of our studies is the realization that endothelial cells within each organ are functionally different, and once activated produce a unique set of growth factors," states Dr. Rafii. "The challenge that lies ahead is to discover the organ-specific growth factors produced by the endothelial cells that initiate the regeneration of that particular organ. Then, these factors could be exploited therapeutically to induce selective regeneration of one organ without affecting others."

Additional co-authors include Daniel J. Nolan, Jason M. Butler, Daylon James, Alexander O. Babazadeh and Koji Shido, all of the Ansary Stem Cell Institute in the Department of Genetic Medicine, Weill Cornell Medical College, and the Howard Hughes Medical Institute; Dr. Vivek Mittal, Department of Surgery, Weill Cornell Medical College; and Dr. Thomas N. Sato, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Nara, Japan.

How Vascular Endothelial Cells Renew Blood Stem Cells and Control Stem Cells' Differentiation

Another study by the same group, published in the Oct. 24 issue of Nature Cell Biology, examines how a similar type of sinusoidal endothelial cells that promote liver regeneration also are activated to renew blood stem cells and control their differentiation into various types of blood cells within the bone marrow. The findings may be used to create mass quantities of stem cells following trauma to the bone marrow's microenvironment.

Following injury from therapeutic radiation or chemotherapy, stem cells in the bone marrow are injured, hampering blood cell production. Some patients experience severe and potentially irreversible trauma to their ability to produce blood cells. Until now it has been unclear how the body signals these stem cells to regenerate and to differentiate into cells that form blood cells.

Dr. Rafii and his lab have shown that endothelial cells release specific angiocrine growth factors into the environment of the bone marrow, telling the body to produce more stem cells. The researchers showed that the Akt-pathway is activated in the endothelial cells, which turns on expression of a group of growth factors that induces the bone marrow to produce more stem cells. Following the activation of the Akt-pathway, the MAP kinase pathway is activated, which stimulates the production of angiocrine factors that control the differentiation of the stem cells into various cells needed to make up blood.

Results from the study show a 10-fold increase of stem cell production in mouse models that express higher levels of Akt selectively in endothelial cells, when compared with control mice. If proven applicable in humans, the findings may lead to a new way of treating patients suffering from bone marrow deficiencies.

"You are essentially creating a cell culture bioreactor capable of producing large numbers of stem cells as well as mature blood cells, which can restore bone marrow following trauma," says Dr. Jason Butler, who along with Dr. Hideki Kobayashi is the study's co-first author and senior postdoctoral fellows in Dr. Rafii's lab.

"Using properly activated organ-specific endothelial cells to propagate enough stem and progenitor cells, such as those of bone marrow and liver, so they can be used clinically has broad therapeutic implications not only for regenerative medicine, but also for the study of genetic diseases," concludes Dr. Rafii.

Additional co-authors include Mariko Kobayashi, Bi-Sen Ding, Bryant Bonner, Vi Chiu, Daniel Nolan, Koji Shido, all from Weill Cornell; and Laura Benjamin and Rebekah O'Donnell, from the Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Mass.

The Nature and Nature Cell Biology studies were both supported by grants from the Howard Hughes Medical Institute, the Ansary Stem Cell Institute, the National Institutes of Health, Qatar National Priorities Research Program, the Anbinder Foundation, Newman's Own Foundation, the Empire State Stem Cell Board, and the New York State Department of Health.

Journal References:

1. Hideki Kobayashi, Jason M. Butler, Rebekah O'Donnell, Mariko Kobayashi, Bi-Sen Ding, Bryant Bonner, Vi K. Chiu, Daniel J. Nolan, Koji Shido, Laura Benjamin, Shahin Rafii. Angiocrine factors from Akt-activated endothelial cells balance self-renewal and differentiation of haematopoietic stem cells. Nature Cell Biology, 2010; 12 (11): 1046 DOI: 10.1038/ncb2108

2. Bi-Sen Ding, Daniel J. Nolan, Jason M. Butler, Daylon James, Alexander O. Babazadeh, Zev Rosenwaks, Vivek Mittal, Hideki Kobayashi, Koji Shido, David Lyden, Thomas N. Sato, Sina Y. Rabbany, Shahin Rafii. Inductive angiocrine signals from sinusoidal endothelium are required for liver regeneration. Nature, 2010; DOI: 10.1038/nature09493

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