Cardiac stem cell therapy closer to reality

Cardiac stem cell therapy closer to reality Thursday, 27 December 2007 Since the year 2000, much has been learned about the potential for using transplanted cells in therapeutic efforts to treat varieties of cardiac disorders. With many questions remaining, the current issue of CELL TRANSPLANTATION (Vol.16 No. 9), The Proceedings of the Third Annual Conference on Cell Therapy for Cardiovascular Disease, presents research aimed at answering some of them. Eleven papers were included in this issue; the four below represent a sample. Bench to Bedside “Cardiac stem cell therapy involves delivering a variety of cells into hearts following myocardial infarction or chronic cardiomyopathy,” says Amit N. Patel, MD, MS, director of cardiac cell therapy at the University of Pittsburgh Medical Center and lead author of an overview and introductory article, Cardiac Stem Cell Therapy from Bench to Bedside. “Many questions remain, such as what types of cells may be most efficacious. Questions about dose, delivery method, and how to follow transplanted cells once they are in the body and questions about safety issues need answers. The following studies, contribute to the growing body of data that will move cell transplantation for heart patients closer to reality.” According to Patel, special editor for this issue, suitable sources of cells for cardiac transplant will depend on the types of diseases to be treated. For acute myocardial infarction, a cell that reduces myocardial necrosis and augments vascular blood flow will be desirable. For heart failure, cells that replace or promote myogenesis, reverse apoptotic mechanisms and reactivate dormant cell processes will be useful. “Very little data is available to guide cell dosing in clinical studies,” says Patel. “Pre-clinical data suggests that there is a dose-dependent improvement in function.” Patel notes that the availability of autologous (patient self-donated) cells may fall short. Determining optimal delivery methods raise issues not only of dose, but also of timing. Also, assessing the fate of injected cells is “critical to understanding mechanisms of action.” Will cells home to the site of injury? Labelling stem cells with durable markers will be necessary and new tracking markers may need to be developed.

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Improved cell survival drugs Adult bone marrow-derived mesenchymal stem cells (MSCs) have shown great signalling and regenerative properties when delivered to heart tissues following a myocardial infarction (MI). However, the poor survival of grafted cells has been a concern of researchers. Given the poor vascular supply after a heart attack and an active inflammatory process, grafted cells survive with difficulty. Transmyocardial revascularisation (TMR), a process by which channels are created in heart tissues by laser or other means, can enhance oxygenated blood supply. “We hypothesized that using TMR as a scar pre-treatment to cell therapy might improve the microenvironment to enhance cell retention and long-term graft success,” said Amit N. Patel, lead author of a study titled Improved Cell Survival in Infarcted Myocardium Using a Novel Combination Transmyocardial Laser and Cell Delivery System. “TMR may act synergistically with signalling factors to have a more potent effect on myocardial remodelling.” Patel and colleagues, who used a novel delivery system to disperse cells in the TMR-generated channels in an animal model, report significant cell survival in the TMR+Cell group versus Cells or TMR alone. The researchers speculated that there was an increase in local production of growth factors that may have improved the survival of transplanted cells. Contact: Amit N. Patel, MD, MS, director of cardiac cell therapy, University of Pittsburgh Medical Center, McGowan Institute of Regenerative Medicine, 200 Lothrop Street – PUH C-700, Pittsburgh, PA 15213 TEL: 412-648-6411 Email: patelan@upmc.edu

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Stem cells depolarize Recent studies have suggested that there are stem cells in the heart. In this study, researchers engineered mesenchymal stem cells (MSC) to over express stromal cell-derived factor-1 (SDF-1), a chemokine. “Our study suggests that the prolongation of SDF-1 expression at the time of an acute myocardial infarction (AMI) leads to the recruitment of what may be an endogenous stem cell in the heart,” says Marc Penn, MD, PhD, director of the Skirball Laboratory for Cardiovascular Cellular Therapeutics at the Cleveland Clinic Foundation. “These cells may contribute to increased contractile function even in their immature stage.” In the study titled SDF-1 Recruits Cardiac Stem Cell Like Cells that Depolarize in Vivo, researchers concluded that there is a natural but inefficient stem cell-based repair process following an AMI that can be manipulated through the expression of key molecular pathways. The outcome of this inefficient repair can have a significant impact on the electrical and mechanical functions of the surviving myocardium. Contact: Marc Penn, MD, PhD, director, Skirball Laboratory for Cardiovascular Cellular Therapeutics, NE3, Departments of Cardiovascular Medicine and Cell Biology, Cleveland Clinic Foundation, 9500 Euclid Ave., Cleveland, Ohio, 44195. TEL: 216-444-7122 Email: pennmn@ccf.org

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Grafting bioartifical myocardium for myocardial assistance While the object of cell transplantation is to improve ventricular function, cardiac cell transplantation has had limited success because of poor graft viability and low cell retention. In a study carried out by a team of researchers from the Department of Cardiovascular Surgery, Pompidou Hospital, a matrix seeded with bone marrow cells (BMC) was grafted onto the infarcted ventricle to help support and regenerate post-ischemic lesions. “Our study demonstrated that bone marrow cell therapy associated with the surgical implantation onto the epicardium of a cell-seeded collagen type 1 matrix prevented myocardial wall thinning, limited post-ischemic remodelling and improved diastolic function,” says Juan Chachques, MD, PhD, lead author for Myocardial Assistance by Grafting a New Bioartificial Upgraded Myocardium (MAGNUM Clinical Trial): One year follow-up. “The use of the biomaterial appears to create a micro atmosphere where both exogenous and endogenous cells find an optimal microenvironment to repair tissues and maintain low scar production,” explains Chachques. According to Chachques, the favourable effects may be attributed to several mechanisms. The BMC seeded in the collagen matrix may be incorporated into the myocardium through epicardial channels created at the injection sites. Too, the cell-seeded matrix may help prevent apoptosis. “This biological approach is attractive because of its potential for aiding myocardial regeneration with a variety of cell types,” concluded Chachques. Those cell types include skeletal myoblasts, bone marrow-derived mesenchymal stem cells, circulating blood-derived progenitor cells, endothelial and mesothelial cells, adipose tissue stem cells and, potentially, embryonic stem cells. Contact: Juan C. Chachques, MD, PhD, Department of Cardiovascular Surgery, Pompidou Hospital, 20 rue Leblanc, 75015 Paris, France. TEL: ++33613144398 Email: j.chachques@brs.aphp.fr

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“Cardiac stem cell repair is one of the most important new areas of research today,” says Cell Transplantation editor Paul Sanberg, PhD, DSc. “This special issue illustrates important new findings and the significant efforts being taken to develop these therapies and move them from the scientist’s bench to the bedside where in clinical practice they can make a difference in the lives of patients.” 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. Contact: Paul Sanberg, PhD., DSc at psanberg@health.usf.edu ......... ZenMaster

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California Company Creates Parthenogenetic hESC Lines

California Company Creates Parthenogenetic hESC Lines Thursday, 20 December 2007 Scientists at California-based International Stem Cell Corporation (ISCO) have created unique human stem cell lines that make them easily “immune matched” to human beings and could enable the creation of a bank of stem cells that could be used, without rejection, by a majority of the different people and races of the world. Akin to the concept of finding multiple “universal Type O blood donors”, the discovery is significant because it would eliminate the need for harsh immune suppression drugs currently used for cell transplant therapy. This may open the door to cell transplant therapy for diseases such as juvenile diabetes where the use of immune suppressant drugs is harmful to the patient. The findings are outlined in a scientific peer review paper entitled “HLA Homozygous Stem Cell Lines Derived from Human Parthenogenetic Blastocysts” which was announced in the December 19, 2007 online edition of Cloning and Stem Cells Journal. Of four unique human stem cell lines created, one line identified as hpSC-Hhom-4 was found to be a match with common immune types found in various races across the United States, opening the door to wide application in human therapeutics. The paper reports that for the Hhom-4 line, for example, therapeutic applications could be beneficial for tens of millions of people in the United States alone. “We are excited about this finding as it moves us closer to being able to cross-match stem cells for human transplant and build a true stem cell bank that could offer on-demand delivery of stem cells matched to a patient’s own immune system and eliminate the need for immunosuppressant drugs,” said Jeff Krstich, CEO of International Stem Cell Corporation. “Our intent is to begin clinical safety studies in animals immediately and utilize these hpSC-Hhom (or Hhom) cell lines to advance the field of regenerative medicine, as well as to commercialize our cells for cell transplant therapies.” One of the greatest risks with all transplants is immune rejection, notes Jeffrey Janus, Director of Scientific Research and co-author of the paper. “Immune suppressant drugs are usually required that result in a precarious balance that involves intentional compromise of the patient’s immune system to keep the body from rejecting the transplant, while still maintaining an immune system strong enough to defend against opportunistic infections and disease.” It is far more complicated in children, he added. “Children are more sensitive to the harsh effects of immune-suppressant drugs, thereby reducing therapeutic options and positive outcomes.” Transplant-based stem cell therapies face the same immune matching challenges as those faced by patients undergoing tissue and organ transplants. This makes ISCO’s creation of the Hhom stem cell lines a significant step toward achieving successful donor stem cell transplants. These new stem cell lines were created by ISCO lead scientist Dr. Elena Revazova using a process called “parthenogenesis”, which utilizes unfertilized human eggs and doesn’t destroy fertilized human embryos. International Stem Cell Corporation on June 27, 2007 announced that Dr. Revazova, one of the world’s leading cell biologists, had led a team in the first deliberate creation of human parthenogenetic stem lines. That breakthrough was outlined in a peer review paper entitled “Patient-Specific Stem Cell Lines Derived from Human Parthenogenetic Blastocysts”, and published in Cloning and Stem Cells Journal. That process then led to the current creation of the Hhom cell lines, which represent a “next major step” advancement of ISCO’s original parthenogenetic breakthrough. Data presented shows that the four new stem cell lines function similarly to those derived from fertilized human embryos and have the capacity to differentiate into the three germ layers of the body, meaning they have the ability to become any human cell type. Future work is focused on differentiating the Hhom cell lines into therapeutically useful cells. Although these Hhom lines are virtually animal contaminant free — a distinction likely to be critical for meeting Federal Drug Administration (FDA) approval for human clinical trials — the biggest advantage is that these parthenogenetically-derived stem cells have a simplified genetic code in the critical “HLA region” of the DNA, the region that gives a cell its immune profile to the outside world. The overall result produces a cell that is more easily matched with the immune systems of a far greater percentage of a population group. The paper reports that “with proper selection of oocyte donors according to HLA haplotype, and FDA approved manufacturing protocols, it is possible to generate a bank of cell lines whose tissue derivatives collectively could be MHC-matched with a significant number of individuals.” In explaining how the cell lines may be applied in populations worldwide, the paper notes: “It has been suggested that a panel of only ten HLA homozygous human stem cell lines selected for common types can provide a complete HLA-A, HLA-B and HLA-DR match for 37.7% of United Kingdom recipients, and a beneficial match for 67.4%.” In addressing the US population, the paper notes, “…calculations suggest that there are close to 200 common haplotypes per racial group. The hpSC-Hhom-4 line carries one of the most common haplotypes.” “We believe that Hhom lines are ideally suited for establishing a repository — a stem cell bank — of differentiated cells and tissues HLA-matched to population groups, which could be available for immediate clinical application,” added Krstich. “ISCO’s discovery significantly reduces the number of necessary stem cell lines needed to treat vast numbers of people. Moreover, the process is relatively efficient and reproducible.” The paper reports that aside from regenerative therapy, “a repository of cells and tissues derived from Hhom lines may be invaluable in the treatment of genetic disorders, “…including Alzheimer’s disease, diabetes, Graves disease, haemophilia, Huntington’s Disease, muscular dystrophy, Parkinson’s disease, sickle cell anaemia, Phenylketonuria-PKU and Severe Combined Immune Deficiency (SCID). Scientists must first change or “differentiate” the Hhom stem cells into the proper cell type to cure these diseases, but the Hhom lines should provide the best starting point for these studies. ......... See also: Chinese Groups Make Parthenogenetic hESCs Comments: More new lines of human parthenogenetic embryonic stem cells Cell Research (2008) 18:215–217. doi: 10.1038/cr.2008.19; published online 4 February 2008 ......... ZenMaster

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The Latest About Synthetic Life

Read The Latest About Synthetic Life Synthetic DNA on the Brink of Yielding New Life Forms Washington Post - Monday, December 17, 2007 ......... ZenMaster For more on stem cells and cloning, go to CellNEWS at http://www.geocities.com/giantfideli/index.html

Chinese Groups Make Parthenogenetic hESCs

Two Chinese Groups Make Parthenogenetic hESCs Thursday, 13 December 2007 Two Chinese groups report this week, in the journal Cell Research, that they have obtained homozygous human ESC lines from a parthenogenetic oocyte, a process by which an oocyte is activated to develop without fusing with a sperm. Homozygous human embryonic stem cells (hESCs) are thought to be better cell sources for hESC banking because their histocompatibility would make it much more easy of finding matches for certain populations with relatively smaller groups of cell lines. Therefore they will be an important source of histocompatible cells and tissues for cell therapy in the future. The first group is lead by Guangxiu Lu at Central South University in Changsha, China. She has for a long period of time already worked with embryonic stem cells, and even claimed to have produced cloned human embryos several years ago. The other group is Shu-zhen Huang’s at the Institute of Medical Genetics, Shanghai Jiao Tong University School of Medicine, together with Qi Zhou’s laboratory in Beijing at the State Key Laboratory of Reproductive Biology, Institute of Zoology, the Chinese Academy of Sciences. Shu-zhen Huang is known for having created human-rabbit mixed embryos some years ago. Guangxiu Lu’s groups describe one cell line, while the other group succeeded to make two different cell lines. Both groups has carefully and detailed characterized their cells and determined they are of parthenogenetic origin by several techniques. References: A highly homozygous and parthenogenetic human embryonic stem cell line derived from a one-pronuclear oocyte following in vitro fertilization procedure Ge Lin, Qi OuYang, Xiaoying Zhou, Yifan Gu, Ding Yuan, Wen Li, Gang Liu, Tiancheng Liu & Guangxiu Lu Cell Res 2007 17: 999-1007; 10.1038/cr.2007.97 Derivation of human embryonic stem cell lines from parthenogenetic blastocysts Qingyun Mai, Yang Yu, Tao Li, Liu Wang, Mei-jue Chen, Shu-zhen Huang, Canquan Zhou & Qi Zhou Cell Res 2007 17: 1008-1019; 10.1038/cr.2007.102 Comments: More new lines of human parthenogenetic embryonic stem cells Cell Research (2008) 18:215–217. doi: 10.1038/cr.2008.19; published online 4 February 2008 ......... ZenMaster

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Embryonic Stem Cells Repair Heart

Scientists overcome obstacles to embryonic stem cell heart repair Thursday, 13 December 2007 Scientists funded by the Biotechnology and Biological Sciences Research Council (BBSRC) at Imperial College London have overcome two significant obstacles on the road to harnessing stem cells to build patches for damaged hearts. Presenting the research at a UK Stem Cell Initiative conference today (13 December) in Coventry, research leader Professor Sian Harding will explain how her group have made significant progress in maturing beating heart cells (cardiomyocytes) derived from embryonic stem cells and in developing the physical scaffolding that would be needed to hold the patch in place in the heart in any future clinical application. From the outset the Imperial College researchers have been aiming to solve two problems in the development of a stem cell heart patch. The first is undesirable side effects, such as arrhythmia, that can result from immature and undeveloped cardiomyocytes being introduced to the heart. The second is the need for a scaffold that is biocompatible with the heart and able to hold the new cardiomyocytes in place while they integrate into the existing heart tissue. Matching the material to human heart muscle is also hoped to prevent deterioration of heart function before the cells take over. Professor Harding will tell the conference that the stem cell team, led by Dr Nadire Ali, co-investigator on the grant, have managed to follow beating embryonic stem cell-derived cardiomyocytes for up to seven months in the laboratory and demonstrate that these cells do mature. In this period the cells have coordinated beating activity, and they adopt the mature controls found in the adult heart by approximately four months after their generation from embryonic stem cells. These developed cardiomyocytes will then be more compatible with adult heart and less likely to cause arrhythmias. The team have also overcome hurdles in the development of a biocompatible scaffold. Working closely with a group of biomaterial engineers, led by Dr Aldo Boccaccini and Dr Qizhi Chen, co-investigators on the grant, in the Department of Materials, Imperial College London, they have developed a new biomaterial with high level of biocompatibility with human tissue, tailored elasticity and programmable degradation. The latter quality is important as any application in the heart needs to be able to hold cells in place long enough for them to integrate with the organ but then degrade safely away. The researchers have found that their material, which shares the elastic characteristics of heart tissue, can be programmed to degrade in anything from two weeks upwards depending on the temperatures used during synthesis. Professor Harding said: “Although we are still some way from having a treatment in the clinic we have made excellent progress on solving some of the basic problems with stem cell heart therapies. The work we have done represents a step forward in both understanding how stem cell-derived developing heart cells can be matured in the laboratory and how materials could be synthesised to form a patch to deliver them to damaged areas of the heart.” “A significant amount of hard work and research remains to be done before we will see this being used in patients but the heart is an area where stem cell therapies offer promise. We know that the stem cell-derived cardiomyocytes will grow on these materials, and the next step is to see how the material and cell combination behave in the long term.” Professor Nigel Brown, BBSRC Director of Science and Technology, commented: “This research shows that although embryonic stem cell therapies are still some way away from the clinic, progress is being made on the basic biological developments. As with all new biomedical applications, an understanding of the underpinning fundamental science is essential to successfully moving forward.” Note: An image of human embryonic stem cell derived cardiomyocytes and video footage of beating heart stem cells in culture are available to download from BBSRC’s website. ......... ZenMaster

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Stem cells for Duchenne muscular dystrophy?

Reprogrammed human adult stem cells rescue diseased muscle in mice Wednesday, 12 December 2007 Scientists report that adult stem cells isolated from humans with muscular dystrophy can be genetically corrected and used to induce functional improvement when transplanted into a mouse model of the disease. The research, published by Cell Press in the December issue of Cell Stem Cell, represents a significant advance toward the future development of a gene therapy that uses a patient’s own cells to treat this devastating muscle-wasting disease. Duchenne muscular dystrophy (DMD) is a hereditary disease caused by a mutation in the gene that codes for a muscle protein called dystrophin. Dystrophin is a key structural protein that helps to keep muscle cells intact. DMD is characterized by a chronic degeneration of skeletal muscle cells that leads to progressive muscle weakness. Although intense research has focused on finding a way to replace the defective dystrophin protein, at this time there is no cure for DMD. A research group led by Dr. Yvan Torrente from the University of Milan used a combination of cell- and gene-based therapy to isolate adult human stem cells from DMD patients and engineer a genetic modification to correct the dystrophin gene. “Use of the patient’s own cells would reduce the risk of implant rejection seen with transplantation of normal muscle-forming cells,” explains Dr. Torrente. Muscle stem cells, identified by expression of the CD133 surface marker, were isolated from normal and dystrophic human blood and skeletal muscle. The isolated human muscle progenitors were implanted into the muscles of mice and were successfully recruited into muscle fibers. As expected, the CD133+ cells isolated from DMD patients expressed the mutated gene for dystrophin and gave rise to muscle cells that resembled muscle fibers in DMD patients. The researchers then used a sophisticated genetic technique to repair the mutated dystrophin gene in the isolated DMD CD133+ cells so that dystrophin synthesis was restored. Importantly, intramuscular or intra-arterial delivery of the genetically corrected muscle cell progenitors resulted in significant recovery of muscle morphology, function, and dystrophin expression in a mouse model of muscular dystrophy. “These data demonstrate that genetically engineered blood or muscle-derived CD133+ cells represent a possible tool for future stem cell-based autograft applications in humans with DMD,” says Dr. Torrente. The authors caution that significant additional work needs to be done prior to using this technology in humans. “Additional research will substantially enhance our understanding of the mechanisms underlying this effect and may lead to the improvement of gene and cell therapy strategies for DMD.” ......... ZenMaster

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More 'functional' DNA in genome than previously thought

More 'functional' DNA in genome than previously thought Tuesday, 11 December 2007 Surrounding the small islands of genes within the human genome is a vast sea of mysterious DNA. While most of this non-coding DNA is junk, some of it is used to help genes turn on and off. As reported online this week in Genome Research, Hopkins researchers have now found that this latter portion, which is known as regulatory DNA and contributes to inherited diseases like Parkinson’s or mental disorders, may be more abundant than we realize. By conducting an exhaustive analysis of the DNA sequence around a gene required for neuronal development, Andrew McCallion, Ph.D., an assistant professor in the McKusick-Nathans Institute of Genetic Medicine, and his team found that current computer programs that scan the genome looking for regulatory DNA can miss more than 60 percent of these important DNA regions. The current methods find regulatory sequences by comparing DNA from distantly related species, under the theory that functionally important regions will appear more similar in sequence than non-functional regions. “The problem with this approach, we have discovered,” says McCallion, “is that it’s often throwing the baby out with the bath water. So while we believe sequence conservation is a good method to begin finding regulatory elements, to fully understand our genome we need other approaches to find the missing regulatory elements.” McCallion had suspected that using sequence conservation would overlook some regulatory DNA, but to see how much, he set up a small pilot project looking at the phox2b gene; he chose this gene both because of its small size and his interest in nerve development (phox2b is involved in forming part of the brain associated with stress response as well as nerves that control the digestive system). The researchers created what they call a “tiled path,” cutting up the DNA sequence around the phox2b gene into small pieces, then inserted each piece into zebrafish embryos along with a gene for a fluorescent protein. If a phox2b fragment was a regulatory element, then it would cause the protein to glow. By watching the growing fish embryos - which have the advantage of being transparent - the researchers could see which pieces were regulators. They uncovered a total of 17 discrete DNA segments that had the ability to make fish glow in the right cells. The team then analyzed the entire region around the phox2b gene using the five commonly used computer programs that compute sequence conservation; these established methods picked up only 29 percent to 61 percent of the phox2b regulators McCallion identified in the zebrafish experiments. “Our data supports the recent NIH encyclopaedia of DNA elements project, which suggests that many DNA sequences that bind to regulatory proteins are in fact not conserved,” says McCallion. “I hope this pilot shows that these types of analyses can be worthwhile, especially now that they can be done quickly and easily in zebrafish.” McCallion is now planning a larger study of other neuronal genes. “I think we are only starting to realize the importance and abundance of regulatory elements; by regulating the gene activity in each cell they help create the diverse range of cell types in our body.” ......... ZenMaster

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Reprogrammed adult cells treat sickle-cell anaemia in mice

Proof of principle for therapeutic use of induced pluripotent stem cells Friday, 07 December 2007 Mice with a human sickle-cell anaemia disease trait have been treated successfully in a process that begins by directly reprogramming their own cells to an embryonic-stem-cell-like state, without the use of eggs. This is the first proof-of-principle of therapeutic application in mice of directly reprogrammed “induced pluripotent stem” (iPS) cells, which recently have been derived in mice as well as humans. The research, reported in Science Express online on December 6, was carried out in the laboratory of Whitehead Member Rudolf Jaenisch. The iPS cells were derived using modifications of the approach originally discovered in 2006 by the Shinya Yamanaka laboratory at Kyoto University. The scientists studied a therapeutic application of iPS cells with the sickle-cell anaemia model mouse developed by the laboratory of Tim Townes of the University of Alabama at Birmingham. Sickle-cell anaemia is a disease of the blood marrow caused by a defect in a single gene. The mouse model had been designed to include relevant human genes involved in blood production, including the defective version of that gene. To create the iPS cells, the scientists started with cells from the skin of the diseased mice, explains lead author Jacob Hanna, a postdoctoral researcher in the Jaenisch lab. These cells were modified by a standard lab technique employing retroviruses customized to insert genes into the cell’s DNA. The inserted genes were Oct4, Sox2, Lif4 and c-Myc, known to act together as master regulators to keep cells in an embryonic-stem-cell-like state. iPS cells were selected based on their morphology and then verified to express gene markers specific to embryonic stem cells. To decrease or eliminate possible cancer in the treated mice, the c-Myc gene was removed by genetic manipulation from the iPS cells. Next, the researchers followed a well-established protocol for differentiating embryonic stem cells into precursors of bone marrow adult stem cells, which can be transplanted into mice to generate normal blood cells. The scientists created such precursor cells from the iPS cells, replaced the defective blood-production gene in the precursor cells with a normal gene, and injected the resulting cells back into the diseased mice. The blood of treated mice was tested with standard analyses employed for human patients. The analyses showed that the disease was corrected, with measurements of blood and kidney functions similar to those of normal mice. “This demonstrates that iPS cells have the same potential for therapy as embryonic stem cells, without the ethical and practical issues raised in creating embryonic stem cells,” says Jaenisch. While iPS cells offer tremendous promise for regenerative medicine, scientists caution that major challenges must be overcome before medical applications can be considered. First among these is to find a better delivery system, since retroviruses bring other changes to the genome that are far too random to let loose in humans. “We need a delivery system that doesn’t integrate itself into the genome,” says Hanna. “Retroviruses can disrupt genes that should not be disrupted or activate genes that should not be activated.” Potential alternatives include other forms of viruses, synthesized versions of the proteins created by the four master regulator genes that are modified to enter the cell nucleus, and small molecules, Hanna says. Despite the rapid progress being made with iPS cells, Jaenisch emphasizes that this field is very young, and that it’s critical to continue full research on embryonic stem cells as well. “We wouldn’t have known anything about iPS cells if we hadn’t worked with embryonic stem cells,” says Jaenisch. “For the foreseeable future, there will remain a continued need for embryonic stem cells as the crucial assessment tool for measuring the therapeutic potential of iPS cells.” Reference: Treatment of Sickle-Cell Anaemia Mouse Model with iPS Cells Generated from Autologous Skin Science Express online, December 6, 2007 ......... ZenMaster

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Replacing the Cells Lost in Parkinson Disease

Replacing the Cells Lost in Parkinson Disease Wednesday, 05 December 2007 Parkinson disease (PD) is caused by the progressive degeneration of brain cells known as dopamine (DA) cells. Replacing these cells is considered a promising therapeutic strategy. Although DA cell–replacement therapy by transplantation of human foetal mesencephalic tissue has shown promise in clinical trials, limited tissue availability means that other sources of these cells are needed. Now, Ernest Arenas and colleagues at the Karolinska Institute, together with Olle Lindvall’s group at the Wallenberg Neuroscience Center in Lund, Sweden, have identified a new source for DA cells that provided marked benefit when transplanted into mice with a PD-like disease. In the study, DA cells were derived from ventral midbrain (VM) neural stem cells/progenitors by culturing them in the presence of a number of growth factors — FGF2, sonic hedgehog, and FGF8 — and engineering them by transfection to express Wnt5a. This protocol generated 10-fold more DA cells than did conventional FGF2 treatment. These cells exhibited the transcriptional and biochemical profiles and intrinsic electrophysiological properties of midbrain DA cells. Further analysis revealed that these cells initiated substantial cellular and functional recovery when transplanted into mice with PD-like disease. Importantly, the mice did not develop tumours, a potential risk that has precluded the clinical development of embryonic stem cells as a source of DA cells. These data led the authors to suggest that Wnt5a-treated neural stem cells might be an efficient and safe source of DA cells for the treatment of individuals with PD. Reference: Wnt5a-treated midbrain neural stem cells improve dopamine cell replacement therapy in parkinsonian mice J Clin Invest. Published online 2007 December 3. doi: 10.1172/JCI32273. ......... ZenMaster

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Human embryonic stem cells mend massive skull injury

Human embryonic stem cells mend massive skull injury in mice Sunday, 02 December 2007 Broken skulls can be repaired using cells from human embryos, scientists have shown. Researchers were able to plug holes in the skulls of mice by transplanting human embryonic stem cells (hESCs), which grew into new bone tissue. Although at an early stage, the experiment indicated one way that hESCs, or cells like them, might be used in practical treatments. Healing critical-size defects (defects that would not otherwise heal on their own) in intramembraneous bone, the flat bone type that forms the skull, is a vivid demonstration of new techniques devised by researchers at John Hopkins University to use hESCs for tissue regeneration. Using mesenchymal precursor cells isolated from hESCs, the Hopkins team steered them into bone regeneration by using “scaffolds,” tiny, three-dimensional platforms made from biomaterials. Physical context, it turns out, is a powerful influence on cell fate. Nathaniel S. Hwang, Jennifer Elisseeff, and colleagues at Whitaker Biomedical Engineering Institute, Department of Biomedical Engineering, at John Hopkins demonstrated that by changing the scaffold materials, they could shift mesenchymal precursor cells into either of the body’s osteogenic pathways: intramembraneous, which makes skull, jaw, and clavicle bone; or endochondral, which builds the “long” bones and involves initial formation of cartilage, which is then transformed into bone by mineralization. Mesenchymal precursor cells grown on an all-polymer, biodegradable scaffold followed the endochondral lineage. Those grown on a composite scaffold made of biodegradable polymers and a hard, gritty mineral called hydroxyapatite went to the intramembraneous side. Biomaterial scaffolds provide a three-dimensional framework on which cells can proliferate and differentiate, secrete extracellular matrix, and form functional tissues, says Hwang. In addition, their known composition allowed the researchers to characterize the extracellular micro-environmental cues that drive the lineage specification. The promise of pluripotent embryonic stem cells for regenerative medicine hangs on the development of such control techniques. Left to themselves, hESCs in culture differentiate wildly, forming a highly mixed population of cell types, which is of little use for cell-based therapy or for studying particular lineages. Conventional hESC differentiation protocols rely on growth factors, co-culture, or genetic manipulation, say the researchers. The scaffolds offer a much more efficient method. As a proof of principle, Hwang and colleagues seeded hESC-derived mesenchymal cells onto hydroxyapatite-composite scaffolds and used the resulting intramembraneous bone cells to successfully heal large skull defects in mice. The Hopkins researchers believe that this is the first study to demonstrate a potential application of hESC-derived mesenchymal cells in a musculoskeletal tissue regeneration application. (Presented at American Society for Cell Biology's 47th Annual Meeting in Washington, D.C., Abstract B312 Biomaterials-directed In Vivo Commitment of Mesenchymal Cells Derived from Human Embryonic Stem Cells. N. S. Hwang, S. Varghese, J. Elisseeff; Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA) ......... ZenMaster

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ESCs produced from fibroblasts without oncogenes

Japanese group make induced pluripotent stem cells from fibroblasts without oncogenes Saturday, 01 December 2007 The Japanese journal Yomiuri Shimbun report that Prof. Shinya Yamanaka from A Kyoto University now have produced induced pluripotent stem cells, or iPS cells, from skin cells of humans and mice without using cancer-causing oncogene c-Myc. The team, led by Prof. Shinya Yamanaka, says its research shows iPS cells produced by their new method are less likely to develop cancer-inducing properties. The group's paper will be published online Saturday by scientific journal Nature Biotechnology. Read more: Stem cell breakthrough made at Kyoto U. The Yomiuri Shimbun - 01 December 2007 Reference: Generation of induced pluripotent stem cells without Myc from mouse and human fibroblasts Nature Biotechnology 30 November 2007 doi:10.1038/nbt1374 ......... ZenMaster

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