Restoring Vision with Stem Cells

Researchers have succeed in producing photoreceptors from human embryonic stem cells

Tuesday, 06 October 2015

Age-related macular degeneration (AMRD) could be treated by transplanting photoreceptors produced by the directed differentiation of stem cells, thanks to findings published today by Professor Gilbert Bernier of the University of Montreal and its affiliated Maisonneuve-Rosemont Hospital. ARMD is a common eye problem caused by the loss of cones. Bernier's team has developed a highly effective in vitro technique for producing light sensitive retina cells from human embryonic stem cells.

"Our method has the capacity to differentiate 80% of the stem cells into pure cones," Professor Gilbert explained.

"Within 45 days, the cones that we allowed to grow towards confluence spontaneously formed organised retinal tissue that was 150 microns thick. This has never been achieved before."

In order to verify the technique, Bernier injected clusters of retinal cells into the eyes of healthy mice. The transplanted photoreceptors migrated naturally within the retina of their host.

Age-related macular degeneration could be

treated by transplanting photoreceptors

produced by the directed differentiation of stem

cells, thanks to findings published today by

Professor Gilbert Bernier of the University of

Montreal and its affiliated Maisonneuve-

Rosemont Hospital. This image illustrates the 3D

reconstruction of the tissue that was produced in

vitro and labelled with antibodies against

photoreceptor-specific proteins. Credit: G.

Bernier, Université de Montréal.

"Cone transplant represents a therapeutic solution for retinal pathologies caused by the degeneration of photoreceptor cells," Bernier explained.

"To date, it has been difficult to obtain great quantities of human cones."

His discovery offers a way to overcome this problem, offering hope that treatments may be developed for currently non-curable degenerative diseases, like Stargardt disease and ARMD.

"Researchers have been trying to achieve this kind of trial for years," he said.

"Thanks to our simple and effective approach, any laboratory in the world will now be able to create masses of photoreceptors. Even if there's a long way to go before launching clinical trials, this means, in theory, that will be eventually be able to treat countless patients."

The findings are particularly significant in the light of improving life expectancies and the associated increase in cases of ARMD. ARMD is in fact the greatest cause of blindness amongst people over the age of 50 and affects millions of people worldwide. And as we age, it is more and more difficult to avoid - amongst people over 80, this accelerated aging of the retina affects nearly one in four. People with ARMD gradually lose their perception of colours and details to the point that they can no longer read, write, watch television or even recognize a face.

ARMD is due to the degeneration of the macula, which is the central part of the retina that enables the majority of eyesight. This degeneration is caused by the destruction of the cones and cells in the retinal pigment epithelium (RPE), a tissue that is responsible for the reparation of the visual cells in the retina and for the elimination of cells that are too worn out. However, there is only so much reparation that can be done as we are born with a fixed number of cones. They therefore cannot naturally be replaced. Moreover, as we age, the RPE's maintenance is less and less effective - waste accumulates, forming deposits.

"Differentiating RPE cells is quite easy. But in order to undertake a complete therapy, we need neuronal tissue that links all RPE cells to the cones. That is much more complex to develop," Bernier explains, noting nonetheless that he believes his research team is up to the challenge.

Bernier has been interested in the genes that code and enable the induction of the retina during embryonic development since completing his PhD in Molecular Biology in 1997.

"During my post-doc at the Max-Planck Institute in Germany, I developed the idea that there was a natural molecule that must exist and be capable of forcing embryonic stem cells into becoming cones," he said.

Indeed, bioinformatics analysis led him to predict the existence of a mysterious protein: COCO, a "recombinational" human molecule that is normally expressed within photoreceptors during their development.

In 2001, he launched his laboratory at Maisonneuve-Rosemont Hospital and immediately isolated the molecule. But it took several years of research to demystify the molecular pathways involved in the photoreceptors development mechanism. His latest research shows that in order to create cones, COCO can systematically block all the signalling pathways leading to the differentiation of the other retinal cells in the eye. It's by uncovering this molecular process that Bernier was able to produce photoreceptors. More specifically, he has produced S-cones, which are photoreceptor prototypes that are found in the most primitive organisms.

Beyond the clinical applications, Professor Bernier's findings could enable the modelling of human retinal degenerative diseases through the use of induced pluripotent stem cells, offering the possibility of directly testing potential avenues for therapy on the patient's own tissues.

Source: University of Montréal

Contact: William Raillant-Clark

Reference:

Differentiation of human embryonic stem cells into cone photoreceptors through simultaneous inhibition of BMP, TGFβ and Wnt signaling

Shufeng Zhou, Anthony Flamier, Mohamed Abdouh, Nicolas Tétreault, Andrea Barabino, Shashi Wadhwa and Gilbert Bernier

Development, 42, 3294-3306, October 1, 2015, doi: 10.1242/dev.125385

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Researchers Grow Cardiac Tissue on 'Spider Silk' Substrate

Researchers Grow Cardiac Tissue on 'Spider Silk' Substrate

Saturday, 11 April 2015

Genetically engineered fibres of the protein spidroin, which is the construction material for spider webs, has proven to be a perfect substrate for cultivating heart tissue cells, Moscow Institute of Physics and Technology researchers found. They discuss their findings in an article that has recently come out in the journal PLOS ONE.

These are heart tissue cells grown on a matrix,

stained with fluorescent markers. Credit: ©

Alexander Teplenin et al./PLOS ONE.

The cultivation of organs and tissues from a patient's cells is the leading edge of medical research - regenerative methods can solve the problem of transplant rejection. However, it’s quite a challenge to find a suitable frame, or substrate, to grow cells on. The material should be non-toxic and elastic and should not be rejected by the body or impede cell growth. A group of researchers led by Professor Konstantin Agladze, who heads the Laboratory of the Biophysics of Excitable Systems at MIPT, works on cardiac tissue engineering. The group has been cultivating fully functional cardiac tissues, able to contract and conduct excitation waves, from cells called cardiomyocytes. Previously, the group used synthetic polymeric nano-fibres but recently decided to assay another material – electro-spun fibres of spidroin, the cobweb protein. Cobweb strands are incredibly light and durable. They're five times stronger than steel, twice more elastic than nylon, and are capable of stretching a third of their length. The structure of spidroin molecules that make up cobweb drag lines is similar to that of the silk protein, fibroin, but is much more durable.

This is a spidroin fibre matrix captured with a

microscope. Credit: Alexander Teplenin et al./

PLOS ONE.

Researchers would normally use artificial spidroin fibre matrices as a substrate to grow implants like bones, tendons and cartilages, as well as dressings. Professor Agladze's team decided to find out whether a spidroin substrate derived from genetically modified yeast cells can serve to grow cardiac cells.

For this purpose, they seeded isolated neonatal rat cardiomyocytes on fibre matrices. During the experiment, the researchers monitored the growth of the cells and tested their contractibility and the ability to conduct electric impulses, which are the main features of normal cardiac tissue.

The monitoring, carried out with the help of a microscope and fluorescent markers, showed that within three to five days a layer of cells formed on the substrate that were able to contract synchronously and conduct electrical impulses just like the tissue of a living heart would.

"We can answer positively all questions we put at the beginning of this research project," Professor Agladze says.

"Cardiac tissue cells successfully adhere to the substrate of recombinant spidroin; they grow forming layers and are fully functional, which means they can contract co-ordinately."

Source: Moscow Institute of Physics and Technology

Contact: Stanislav Goryachev

Reference:

Functional Analysis of the Engineered Cardiac Tissue Grown on Recombinant Spidroin Fiber Meshes

Alexander Teplenin, Anna Krasheninnikova, Nadezhda Agladze, Konstantin Sidoruk, Olga Agapova, Igor Agapov, Vladimir Bogush, Konstantin Agladze

PLOS ONE, March 23, 2015, DOI:10.1371/journal.pone.0121155

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New Cells May Help Treat Diabetes

U. Iowa group creates insulin-producing cells that normalize blood-sugar levels in diabetic mice

Thursday, 29 January 2015

University of Iowa researchers reprogrammed

human skin cells to create induced pluripotent

stem cells, which were then differentiated in a

stepwise fashion to create insulin-producing cells.

When these cells were transplanted into diabetic

mice, the cells secreted insulin and reduced the

blood sugar levels of the mice to normal or near-

normal levels. The image shows the insulin-

producing cells (right) and precursor cells (left).

Credit: University of Iowa.

Starting from human skin cells, researchers at the University of Iowa have created human insulin-producing cells that respond to glucose and correct blood-sugar levels in diabetic mice. The findings may represent a first step toward developing patient-specific cell replacement therapy for type 1 diabetes.

In the new study, published Jan. 28 in the journal PLOS ONE, the UI team led by Nicholas Zavazava, MD, PhD, UI professor of internal medicine, reprogrammed human skin cells to create induced pluripotent stem (iPS) cells, which were then coaxed into forming insulin-producing cells. When these cells were transplanted into diabetic mice, the cells secreted insulin and reduced the blood sugar levels of the mice to normal or near-normal levels.

Although the cells were not as effective as pancreatic cells in controlling blood sugar levels, Zavazava says that the results are an "encouraging first step" toward the goal of generating effective insulin-producing cells that can be used to potentially cure type 1 diabetes.

"This raises the possibility that we could treat patients with diabetes with their own cells," says Zavazava, who also is a member of the Fraternal Order of Eagles Diabetes Research Center at the UI.

"That would be a major advance, which will accelerate treatment of diabetes."

In type 1 diabetes, a person's immune system attacks and destroys the pancreatic beta cells that produce insulin. Although it is possible to treat type 1 diabetes with pancreas transplants from deceased donors, the demand for transplants far exceeds the availability of donated organs.

Zavazava's team is among several groups aiming to create an alternative source of insulin-producing pancreatic cells that can be transplanted into patients with type 1 diabetes. However, the UI study is the first to use human iPS cells to create the insulin-producing cells. Creating these cells from a patient's own cells would not only eliminate the need to wait for a donor pancreas, but would also mean patients could receive transplants without needing to take immunosuppressive drugs. Using iPS cells rather than embryonic stem cells as a starting point also avoids the ethical concerns some people have with using embryonic stem cells.

In the mouse study, the insulin-producing cells were placed under the kidney capsule - a thin membrane layer that surrounds the kidney - where they developed into an organ-like structure with its own blood supply. This new "organ" secreted insulin and gradually corrected the blood sugar levels in the diabetic mice over a period of several months. In addition, after the mice became normoglycemic, the glucose levels stayed steady.

By developing the cells in a stepwise fashion, the UI team was able to collect and use only those cells that would develop into pancreatic cells. This meant they were able to remove very immature (undifferentiated) cells that could form tumours. None of the mice developed tumours from the transplanted cells.

Source: University of Iowa

Contact: Jennifer Brown

Reference:

Human iPS Cell-Derived Insulin Producing Cells Form Vascularized Organoids under the Kidney Capsules of Diabetic Mice

Raikwar SP, Kim E-M, Sivitz WI, Allamargot C, Thedens DR and Nicholas Zavazava

PLoS ONE 10(1): e0116582 (2015), doi:10.1371/journal.pone.0116582

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Mammalian Heart Regenerative Capacity Depends on Severity of Injury

Full recovery and normal function restored in mouse models following mild injury

Friday, 23 January 2015

This is a neonatal mouse heart showing basal

level of proliferating cardiomyocytes. (Red-

cardiomyocytes; Green- proliferating

cardiomyocytes; RV-right ventricle; LV-left

ventricle.) Credit: The Saban Research Institute

of Children's Hospital Los Angeles. 

A new study by researchers at Children's Hospital Los Angeles has shown that neonatal mouse hearts have varying regenerative capacities depending upon the severity of injury. Using cryo-injury - damaging the heart through exposure to extreme cold in order to mimic cellular injury caused by myocardial infarction - investigators found that neonatal mouse hearts can fully recover normal function following a mild injury, though fail to regenerate after a severe injury.

Published online by the journal Developmental Biology, the study suggests that cardiac regeneration strategies should be based on the type and severity of heart injury.

"Using models such as zebrafish and neonatal mice that regenerate their hearts naturally, we can begin to identify important molecules that enhance heart repair," said Ellen Lien, PhD, of The Saban Research Institute of Children's Hospital Los Angeles. Lien, who was senior author on the paper, is also an assistant professor at the Keck School of Medicine of the University of Southern California.

New born mice have shown the capacity for heart regeneration, but it is rapidly lost by seven days after birth. Approaches to extend this regenerative capacity in a mammalian model, from the neonatal period to the juvenile or adult period, could help identify new treatment options for humans.

Acute myocardial infarction, commonly known as a heart attack, can be classified according to the extent of damage to the heart muscle. Severe, or trans-mural injury, is associated with a blood supply blockage to the full thickness of the heart. Non-trans-mural injury indicates a blockage that penetrates only partially through the heart muscle. The investigators were able to develop models for both types of injury.

In addition to differences in regenerative capacity, the investigators also found an indicator of tissue fibrosis or "scarring", profibrotic marker PAI-1, was markedly elevated only after trans-mural injury. In both models post-injury, the cells that form heart muscle, cardiomyocytes, did not increase significantly. However, responses to cardiac injury repair in the outer layer of the heart (epicardium) and blood vessels (revascularization) - were present.

"If we can figure out how to activate this youthful type of myocardial regeneration program in humans, it will be a major clinical breakthrough," said David Warburton, OBE, DSc, MD, director of Developmental Biology and Regenerative Medicine at The Saban Research Institute of CHLA. Warburton is also a professor at the Keck School of Medicine of USC and was co-author on the paper.

Source: Children's Hospital Los Angeles

Contact: Jennifer Jing

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Researchers Grow Functional Tissue-engineered Intestine from Human Cells

Regenerative medicine technique brings surgeons one step closer to helping patients

Thursday, 08 January 2015

This is the principal investigator Tracy C.

Grikscheit of The Saban Research Institute of

Children's Hospital Los Angeles. Credit:

Children's Hospital Los Angeles. 

A new study by researchers at Children's Hospital Los Angeles has shown that tissue-engineered small intestine grown from human cells replicates key aspects of a functioning human intestine. The tissue-engineered small intestine they developed contains important elements of the mucosal lining and support structures, including the ability to absorb sugars, and even tiny or ultra-structural components like cellular connections.

Published online January 8 by the American Journal of Physiology: GI & Liver, the work brings surgeons one step closer to helping human patients using this regenerative medicine technique.

Tissue-engineered small intestine (TESI) grows from stem cells contained in the intestine and offers a promising treatment for short bowel syndrome (SBS), a major cause of intestinal failure, particularly in premature babies and newborns with congenital intestinal anomalies. TESI may one day offer a therapeutic alternative to the current standard treatment, which is intestinal transplantation, and could potentially solve its largest challenges - donor shortage and the need for lifelong immunosuppression.

Tracy C. Grikscheit, MD, a principal investigator in The Saban Research Institute of CHLA and its Developmental Biology and Regenerative Medicine program, is also a pediatric surgeon at Children's Hospital Los Angeles and an assistant professor of surgery at the Keck School of Medicine of the University of Southern California.

Grikscheit aims to help her most vulnerable young patients, including babies who are born prematurely and develop a devastating disease called necrotizing enterocolitis (NEC), where life-threatening intestinal damage requires removal of large portions of the small intestine. Without enough intestinal length, the babies are dependent on intravenous feeding, which is costly and may cause liver damage. NEC and other contributors to intestinal failure occur in 24.5 out of 100,000 live births, and the incidence of SBS is increasing. Nearly a third of patients die within five years.

CHLA scientists had previously shown that TESI could be generated from human small intestine donor tissue implanted into immunocompromised mice. However, in those initial studies - published in July 2011 in the biomedical journal Tissue Engineering, Part A - only basic components of the intestine were identified. For clinical relevance, it remained necessary to more fully investigate intact components of function such as the ability to form a healthy barrier while still absorbing nutrition or specific mechanisms of electrolyte exchange.

The new study determined that mouse TESI is highly similar to the TESI derived from human cells, and that both contain important building blocks such as the stem and progenitor cells that will continue to regenerate the intestine as a living tissue replacement. And these cells are found within the engineered tissue in specific locations and in close proximity to other specialized cells that are known to be necessary in healthy human intestine for a fully functioning organ.

"We have shown that we can grow tissue-engineered small intestine that is more complex than other stem cell or progenitor cell models that are currently used to study intestinal regeneration and disease, and proven it to be fully functional as it develops from human cells," said Grikscheit.

"Demonstrating the functional capacity of this tissue-engineered intestine is a necessary milestone on our path toward one day helping patients with intestinal failure."

Source: Children's Hospital Los Angeles

Contact: Debra Kain

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Reprogramming Cells, Long Term

Positive finding could have major implications for diabetes treatment

Tuesday, 18 November 2014

Harvard Stem Cell Institute (HSCI) researchers, representing five Harvard departments and affiliated institutions as well as the Massachusetts Institute of Technology (MIT), have demonstrated that adult cells, reprogrammed into another cell type in a living animal, can remain functional over a long period.

Joe Zhou is a Harvard Stem Cell Institute

Principal Faculty Member and an Associate

Professor in Harvard's Department of Stem Cell

and Regenerative Biology. Zhou and colleagues

have demonstrated that cells reprogrammed in

vivo can survive, thrive, and be therapeutically

useful. Credit: B. D. Colen/Harvard University.

The work by Joe Zhou, an associate professor in Harvard's Department of Stem Cell and Regenerative Biology, and his collaborators is an important advance in the effort to develop cell-based therapies for tissue repair, and specifically in the effort to develop improved treatment for diabetes.

The researchers used a combination of genes to change pancreatic exocrine cells – one of the main forms of cells in the pancreas – in adult mice that have diabetes into insulin-producing beta cells that appeared to cure about a third of the mice of the metabolic disease, and improved insulin production in most of the other mice. A report on the work was published today in the journal Nature Biotechnology.

The new findings are a major advance in work by HSCI co-director Doug Melton and Zhou, who in 2008 reported having converted exocrine cells into functional beta cells in mice. At that time, however, it was not known how long, and how well, the repurposed cells would function.

"The efficiency of reprogramming has always been an issue," Zhou said.

"Until now, the new cells have either dropped dramatically in number or disappeared completely," he said, noting that since his work with Melton in 2008 there have been reports published in other programing systems that question whether the reprogrammed cells could be stable enough ultimately to be useful.

"What we have demonstrated is that yes, the reprogrammed cells can be useful, and for that to happen you have to create a niche environment in which the cells can survive," Zhou continued.

"We have improved the reprogramming efficiency to a point where one can create a large enough number of the new cells that the new cells create their own niche environment."

Zhou said that the researchers studied the mice for up to about 13 months, approximately half their normal life span, and found that "the cells are still there, and fairly robust. These are diabetic animals, and we were able to, I wouldn't use the word 'cure' because that's a very freighted word for me to use, but they became highly glycaemic animals – though not every animal became normal. That may be because to completely control the glucose level of the animal, you not only need beta cells, you need about a quarter of a million functional beta cells. If you are short of this number, even if the beta cells are perfectly normal," they can't completely control blood sugar levels, Zhou said.

When discussing the implications of the study for the field of cellular reprogramming, Zhou cautioned that the pancreas has a particularly simple cellular organization and structure, and thus findings in the pancreas might not necessarily apply to other organs.

Diabetes is a metabolic disease that is seen in two basic forms.

Type 1 diabetes is an autoimmune disease affecting about 3 million Americans, in which the patient's immune system ultimate destroys all the insulin-producing beta cells in the pancreas, and the patient has to inject insulin in order to regulate blood glucose levels.

Type 2 diabetes, which is now at epidemic prevalence rates in the United States and around the world, is usually caused by being overweight, lack of proper exercise, and improper diet, and can make a patient insulin-resistant, so the insulin the body produces is not sufficient to control blood glucose levels.

If the kind of treatment approach suggested by the new study were to succeed in humans – and that is a question to be answered with further animal, and eventually human, studies – it could be useful in treating both forms of diabetes.

One drawback to the current form of the new approach is that the cellular reprogramming is done with genes, and there might ultimately be unwanted effects on the cells. Zhou said the goal would be to replace the genes with chemicals or, perhaps, RNAs.

"I've talked to many clinicians about whether our approach could be used in humans," Zhou said.

"And the opinion is divided. Some say this could be developed into a human treatment, and some say it should be improved. But there seems to be general agreement that it could potentially be useful."

Source: Harvard University

Contact: B. D. Colen

Reference:

Long-term persistence and development of induced pancreatic beta cells generated by lineage conversion of acinar cells

Weida Li, Claudia Cavelti-Weder, Yinying Zhang, Kendell Clement, Scott Donovan, Gabriel Gonzalez, Jiang Zhu, Marianne Stemann, Ke Xu, Tatsu Hashimoto, Takatsugu Yamada, Mio Nakanishi, Yuemei Zhang, Samuel Zeng, David Gifford, Alexander Meissner, Gordon Weir & Qiao Zhou

Nature Biotechnology (2014), doi:10.1038/nbt.3082

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Salk Scientists Discover a Key to Mending Broken Hearts

Researchers regenerate and heal mouse hearts by using the molecular machinery the animals had all along

Friday, 07 November 2014

Researchers at the Salk Institute have healed injured hearts of living mice by reactivating long dormant molecular machinery found in the animals’ cells, a finding that could help pave the way to new therapies for heart disorders in humans.

An injured zebrafish heart showing proliferating

cells in the wounded area of the heart (red) and

cardiac muscle cells (green). Credit: Courtesy of

the Salk Institute for Biological Studies. 

The new results, published November 6, 2014 in the journal Cell Stem Cell, suggest that although adult mammals don’t normally regenerate damaged tissue, they may retain a latent ability as a holdover, like their distant ancestors on the evolutionary tree. When the Salk researchers blocked four molecules thought to suppress these programs for regenerating organs, they saw a drastic improvement in heart regeneration and healing in the mice.

The findings provide proof-of-concept for a new type of clinical treatment in the fight against heart disease, which kills about 600,000 people each year in the United States – more than AIDS and all cancer types combined, according to the U.S. Centers for Disease Control and Prevention.

“Organ regeneration is a fascinating phenomenon that seemingly recapitulates the processes observed during development. However, despite our current understanding of how embryogenesis and development proceeds, the mechanisms preventing regeneration in adult mammals have remained elusive,” says the study’s senior author Juan Carlos Izpisua Belmonte, a professor in the Gene Expression Laboratory at Salk and holder of the Roger Guillemin Chair.

Within the genomes of every cell in our bodies, we have what information we need to generate an organ. Izpisua Belmonte’s group has for many years focused on elucidating the key molecules involved in embryonic development as well as those potentially underlying healing responses in regenerative organisms such as the zebrafish.

From left: Alejandro Ocampo, Concepcion

Rodriguez Esteban, Juan Carlos Izpisua

Belmonte, Ignacio Sancho-Martinez, Tomoaki

Hishida and Eric Vazquez. Credit: Courtesy of

the Salk Institute for Biological Studies. 

Indeed, back in 2003, Izpisua Belmonte’s laboratory first identified the signals preceding zebrafish heart regeneration. And in a 2010 Nature paper, the researchers described how regeneration occurred in the zebrafish. Rather than stem cells invading injured heart tissue, the cardiac cells themselves were reverting to a precursor-like state (a process called ‘dedifferentiation’), which, in turn, allowed them to proliferate in tissue.

Although in theory it might have seemed like the next logical step to ask whether mammals had evolutionarily conserved any of the right molecular players for this kind of regenerative reprogramming, in practice it was a scientific risk, recalls Ignacio Sancho-Martinez, a postdoctoral researcher in Izpisua Belmonte’s lab.

“When you speak about these things, the first thing that comes to peoples’ minds is that you’re crazy,” he says.

“It’s a strange sounding idea, since we associate regeneration with salamanders and fish, but not mammals.”

Most other studies have looked to the hearts of neonatal mammals for molecular clues about proliferation, to no avail.

“Instead, we thought, ‘If fish know how to do it, there must be something they can teach us about it,’” says the study’s first author Aitor Aguirre, a postdoctoral researcher in Izpisua Belmonte’s group.

In a dish, heart muscle cells return to a precursor-

like state after pro-regenerative treatment with

microRNA inhibitors. Green shows a

disorganized cardiomyocyte cytoskeleton

indicative of cell dedifferentiation; red shows

mitochondrial organization. Credit: Courtesy of

the Salk Institute for Biological Studies. 

The team decided to focus on microRNAs, in part because these short strings of RNA control the expression of many genes. They performed a comprehensive screen for microRNAs that were changing in their expression levels during the healing of the zebrafish heart and that were also conserved in the mammalian genome.

Their studies uncovered four molecules in particular – MiR-99, MiR-100, Let-7a and Let-7c – that fit their criteria. All were heavily repressed during heart injury in zebrafish and they were also present in rats, mice and humans.

However, in studies of mammalian cells in a culture dish and studies of living mice with heart damage, the group saw that the levels of these molecules were high in adults and did not decline with injury. So the team used adeno-associated viruses specific for the heart to target each of those four microRNAs, suppressing their levels experimentally.

Injecting the inhibitors into the hearts of mice that had suffered a heart attack triggered the regeneration of cardiac cells, improving numerous physical and functional aspects of the heart, such as the thickness of its walls and its ability to pump blood. The scarring caused by the heart attack was much reduced with treatment compared to controls, the researchers found.

The improvements were still obvious three and six months after treatment – a long time in a mouse’s life.

“The good thing is that the success was not limited to the short term, which is quite common in cardiac regenerative biology,” Sancho-Martinez says.

The new study focused only on a handful of 70 some microRNA candidates that turned up in the group’s initial screen. These other molecules will likely also play a part in heart cell proliferation, healing scars and promoting the formation of new blood vessels – all processes critical for heart repair, Sancho-Martinez says. The data are available so that other research groups can focus on molecules that interest them.

The next step for Izpisua Belmonte’s team is to move into larger animals and see whether “regenerative reprogramming” can work in larger hearts, and for extended periods after treatment, says Sancho-Martinez. And, although the virus packaging disappeared from the animals’ bodies by 2 weeks after treatment, the scientists are working on a new way to deliver the inhibitors to avoid the need for viruses altogether.

Source: Salk Institute

Reference:

In vivo reprogramming with conserved regenerative effectors promotes robust mammalian heart regeneration

Authors: Aitor Aguirre, Nuria Montserrat, Serena Zachiggna, Emmanuel Nivet, Tomoaki Hishida, Marie Nicole Krause, Leo Kurian, Alejandro Ocampo, Eric Vazquez-Ferrer, Concepcion Rodriguez-Esteban, Sachin Kumar, James J. Moresco, John R. Yates III, Josep Maria Campistol, Ignacio Sancho-Martinez, Mauro Giacca and Juan Carlos Izpisua Belmonte

Cell Stem Cell, Volume 15, Issue 5, p589–604, 6 November 2014, DOI: http://dx.doi.org/10.1016/j.stem.2014.10.003

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New Technique Allows Scientists to Find Rare Stem Cells within Bone Marrow

New Technique Allows Scientists to Find Rare Stem Cells within Bone Marrow

Tuesday, 07 October 2014

Deep within the bone marrow resides a type of cells known as mesenchymal stem cells (MSCs). These immature cells can differentiate into cells that produce bone, cartilage, fat, or muscle — a trait that scientists have tried to exploit for tissue repair.

MIT and SMART researchers have developed a

way to isolate mesenchymal stem cells based on

physical traits such as stiffness. Credit: Image

courtesy of the researchers. 

In a new study that should make it easier to develop such stem-cell-based therapies, a team of researchers from MIT and the Singapore-MIT Alliance in Research and Technology (SMART) has identified three physical characteristics of MSCs that can distinguish them from other immature cells found in the bone marrow. Based on this information, they plan to create devices that could rapidly isolate MSCs, making it easier to generate enough stem cells to treat patients.

Until now, there has been no good way to separate MSCs from bone marrow cells that have already begun to differentiate into other cell types, but share the same molecules on the cell surface. This may be one reason why research results vary among labs, and why stem-cell treatments now in clinical trials are not as effective as they could be, says Krystyn Van Vliet, an MIT associate professor of materials science and engineering and biological engineering and a senior author of the paper, which appears in the Proceedings of the National Academy of Sciences this week.

"Some of the cells that you're putting in and calling stem cells are producing a beneficial therapeutic outcome, but many of the cells that you're putting in are not," Van Vliet says.

"Our approach provides a way to purify or highly enrich for the stem cells in that population. You can now find the needles in the haystack and use them for human therapy."

Lead authors of the paper are W.C. Lee, a former graduate student at the National University of Singapore and SMART, and Hui Shi, a former SMART postdoc. Other authors are Jongyoon Han, an MIT professor of electrical engineering and biological engineering, SMART researchers Zhiyong Poon, L.M. Nyan, and Tanwi Kaushik, and National University of Singapore faculty members G.V. Shivashankar, J.K.Y. Chan, and C.T. Lim.

Physical markers

MSCs make up only a small percentage of cells in the bone marrow. Other immature cells found there include osteogenic cells, which have already begun the developmental path toward becoming cartilage- or bone-producing cells. Currently, researchers try to isolate MSCs based on protein markers found on the cell surfaces. However, these markers are not specific to MSCs and can also yield other types of immature cells that are more differentiated.

"Conventional cell-surface markers are frequently used to isolate different types of stem cells from the human bone marrow, but they lack sufficient 'resolution' to distinguish between subpopulations of mesenchymal stromal cells with distinct functions," Lee says.

The researchers set out to find biophysical markers for multipotency — the ability to become many different cell types. They first suspected that cell size might be a factor, because foetal bone marrow stem cells, which tend to have a higher percentage of MSCs, are usually small in diameter.

To test this hypothesis, the researchers used a device Han had previously developed to capture circulating tumour cells based on their size. They isolated bone marrow cells based on size and found that while none of the larger cells were multipotent, not all of the smaller cells were multipotent, so size alone cannot be used to distinguish MSCs.

After measuring several other physical traits, the researchers found two that could be combined with size to completely distinguish MSCs from other stem cells: stiffness of the cell, and the degree of fluctuation in the cell's nuclear membrane.

"You don't need more than these three, but you also can't use fewer than these three," Van Vliet says.

"We now have a triplet of characteristics that identifies populations of cells that are going to be multipotent versus populations of cells that are only going to be able to become bone or cartilage cells."

These features appear to correspond to what is already known about stem cells, Van Vliet says. Compared with cells that have already committed to their final fate, immature cells have genetic material that moves around inside the nucleus, producing more fluctuations of the nuclear cell membrane. Stem cells also have a less rigid cytoskeletal structure than those of highly differentiated cells, at least when adhered to materials such as glass, making those attached cells seem less stiff.

Better regeneration

The researchers then tested the regenerative abilities of the isolated MSCs in mice. They found that these cells could help repair both muscle and bone injuries, while cells identified as osteogenic stromal cells were able to repair bone but not muscle.

"We have provided the first demonstration that subpopulations of mesenchymal stromal cells can be identified and highly enriched for bone growth and muscle repair," Lee says.

"We envision that this approach would also be important in the selection and purification of bone marrow-derived stem cells for tissue repair in human patients suffering from a range of tissue-degenerative diseases."

The team is now working on high-speed methods for separating MSCs. Creating more pure populations of such cells should lead to more effective stem-cell treatments for tissue injuries, Van Vliet says.

"Instead of putting in 30 percent of the cells that you want, and 70 percent filler, you're putting in 100 percent of the cells that you want," she explains.

"That should lead to more reliable patient outcomes, because you're not going to have this variability from batch to batch, or patient to patient, in how many of each cell population are present."

Van Vliet and Poon also hope to begin a clinical trial of the osteogenic cells isolated in this study, which could prove useful for treating bone injuries.

Source: Massachusetts Institute of Technology

Contact: Sarah McDonnell

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ZenMaster

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For more on stem cells and cloning, go to CellNEWS at

http://cellnews-blog.blogspot.com/

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Stem Cells Show Promise for Stroke Treatment in Pilot Study

Stem Cells Show Promise for Stroke Treatment in Pilot Study

Saturday, 09 August 2014

A stroke therapy using stem cells extracted from patients' bone marrow has shown promising results in the first trial of its kind in humans.

Five patients received the treatment in a pilot study conducted by doctors at Imperial College Healthcare NHS Trust and scientists at Imperial College London.

The therapy was found to be safe, and all the patients showed improvements in clinical measures of disability.

The findings are published in the journal Stem Cells Translational Medicine. It is the first UK human trial of a stem cell treatment for acute stroke to be published.

The therapy uses a type of cell called CD34+ cells, a set of stem cells in the bone marrow that give rise to blood cells and blood vessel lining cells. Previous research has shown that treatment using these cells can significantly improve recovery from stroke in animals. Rather than developing into brain cells themselves, the cells are thought to release chemicals that trigger the growth of new brain tissue and new blood vessels in the area damaged by stroke.

The patients were treated within seven days of a severe stroke, in contrast to several other stem cell trials, most of which have treated patients after six months or later. The Imperial researchers believe early treatment may improve the chances of a better recovery.

A bone marrow sample was taken from each patient. The CD34+ cells were isolated from the sample and then infused into an artery that supplies the brain. No previous trial has selectively used CD34+ cells, so early after the stroke, until now.

Although the trial was mainly designed to assess the safety and tolerability of the treatment, the patients all showed improvements in their condition in clinical tests over a six-month follow-up period.

Four out of five patients had the most severe type of stroke: only four per cent of people who experience this kind of stroke are expected to be alive and independent six months later. In the trial, all four of these patients were alive and three were independent after six months.

Dr Soma Banerjee, a lead author and Consultant in Stroke Medicine at Imperial College Healthcare NHS Trust, said:

"This study showed that the treatment appears to be safe and that it's feasible to treat patients early when they might be more likely to benefit. The improvements we saw in these patients are very encouraging, but it's too early to draw definitive conclusions about the effectiveness of the therapy. We need to do more tests to work out the best dose and timescale for treatment before starting larger trials."

Over 150,000 people have a stroke in England every year. Survivors can be affected by a wide range of mental and physical symptoms, and many never recover their independence.

Stem cell therapy is seen as an exciting new potential avenue of treatment for stroke, but its exact role is yet to be clearly defined.

Dr Paul Bentley, also a lead author of the study, from the Department of Medicine at Imperial College London, said:

"This is the first trial to isolate stem cells from human bone marrow and inject them directly into the damaged brain area using keyhole techniques. Our group are currently looking at new brain scanning techniques to monitor the effects of cells once they have been injected."

Professor Nagy Habib, Principal Investigator of the study, from the Department of Surgery and Cancer at Imperial College London, said:

"These are early but exciting data worth pursuing. Scientific evidence from our lab further supports the clinical findings and our aim is to develop a drug, based on the factors secreted by stem cells, which could be stored in the hospital pharmacy so that it is administered to the patient immediately following the diagnosis of stroke in the emergency room. This may diminish the minimum time to therapy and therefore optimise outcome. Now the hard work starts to raise funds for this exciting research."

Source: Imperial College London 

Contact: Sam Wong

Reference:

Intra-arterial immunoselected CD34+ stem cells for acute ischemic stroke

Soma Banerjee, Paul Bentley, Mohammad Hamady, Stephen Marley, John Davis, Abdul Shlebak, Joanna Nicholls, Deborah A. Williamson, Steen L. Jensen, Myrtle Gordon, Nagy Habib, Jeremy Chataway

Stem Cells Translational Medicine, 2014;3:1-9. http://dx.doi.org/10.5966/sctm.2013-0178

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ZenMaster

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For more on stem cells and cloning, go to CellNEWS at

http://cellnews-blog.blogspot.com/

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