The Hadassah Human
Embryonic Stem Cell
Research Center
Director:
Benjamin E. Reubinoff, M.D., Ph.D.
The Properties of
Human Embryonic Stem Cells
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Human Embryonic Stem Cells Research
Stem cells are immature unspecialized cells that renew themselves for long periods through cell division. Under certain conditions, they can be induced to become mature cells with special functions such as the beating cells of the heart muscle or the insulin-producing cells of the pancreas.
Human embryonic stem cells (hESCs) are derived from early surplus human embryos (5-6 days after fertilization). The embryos used to derive these stem cells were created for infertility treatment purposes through in vitro fertilization (IVF) procedures and were donated to research when they were no longer needed for that purpose.
Human ES cells are unique in the universe since they can self-renew infinitely in culture yet still retain a normal genetic pattern, and also since they have a remarkable potential to develop into all cells and tissues of the human body.
The Potential of hESCs for Transplantation Therapy
Given their unique properties, hESCs are expected to have far- reaching applications in the study of early human development, the development of new drugs, and regenerative medicine. Human ES cell lines can serve as a renewable unlimited donor source of specialized human cells for transplantation therapy.
Human ES cell-derived mature cells could potentially be transplanted to restore tissue function in a wide range of human diseases that are associated with loss of cell function.
These conditions may include neurodegenerative disorders such as Parkinson’s and Alzheimer’s diseases, Multiple Sclerosis, cerebrovascular accidents, spinal cord injuries, as well as heart failure, diabetes mellitus, and others. The number of patients that potentially could benefit from transplantation of hESCs is overwhelming. For example there are over 16 million patients worldwide with neurodegenerative disorders, and over 120 million diabetic patients. Moreover, transplantation of genetically modified hESCs may allow the transfer and expression of foreign genes in target organs in the course of gene therapy.
While the promise of hESCs for cell and gene therapy is remarkable, further extensive research and development are required to exploit their potential for regenerative medicine.
The Hadassah hESC
Research Center
To this end, The Hadassah hESC Research Center was established in 2003 within the Goldyne Savad Institute of Gene Therapy of Hadassah in collaboration with the Department of Obstetrics and Gynecology. The Center is directed by Professor Benjamin Reubinoff from the Department of Gynecology and includes a staff of seventeen technicians, scientists, PhD's and post-doctoral students.
The Goals of the Center
The major objective of the center is to develop the technologies that will eventually allow the utilization of hESCs for transplantation and gene therapy. Other roles are to stimulate and support hESC research activity in Hadassah as well as other institutions in Israel, and to put Hadassah and Israel on the scientific map as a dominant participant producing cutting-edge technology in the area of stem cell research.
The center focuses on the following scientific and academic specific aims:
A. Development of hESCs for transplantation and gene therapy
1. Development of cell lines suitable for clinical trials.
2. Improvement of the technology of stem cell expansion to create bulk cultures suitable for clinical trials.
3. Development of pure populations of differentiated cells.
4. Analysis of function of differentiated cells in animal models of diseases.
5. Development of genetically modified cells for gene therapy.
6. Resolution of safety issues surrounding the potential use of stem cells in transplantation and gene therapy.
7. Overcoming the obstacle of immunorejection.
B. Promotion of stem cell research at Hadassah and Israel
1. To serve as an institutional and national center of multidiscipline collaborative research programs.
2. To provide technical and theoretical assistance, as well as cells and reagents to scientists in Hadassah, Israel and to international collaborators.
3. To establish an educational program in the field of hESCs for students and Residents.
4. To generate new intellectual property (IP) and technology furthering and strengthening Hadassah’s and Israel’s position in the field.
Structure and Operation of the Center
The Center serves as an institutional research facility and as a base for multidiscipline collaborative research efforts. The center provides into this collaborative research effort, its experience, and knowledge in the fields of hESC biology, growth and differentiation. This is combined with specific scientific and clinical expertise in areas such as neural degenerative disorders, diabetes and others, of key scientists from various hospital departments. It is envisioned that this multidisciplinary approach will expedite the development of hESCs for regenerative medicine.
Hadassah’s Contribution to the Field of Human Embryonic Stem Cells
A. Derivation of cell lines
In a cooperative project of Hadassah University Hospital, Monash University (Australia) and the National University of Singapore, Prof Reubinoff and collaborators have developed ES cell lines from early human embryos. We were the second group in the world to develop human embryonic cell lines. Our cell lines were derived in accordance with the stringent NIH Ethical Guidelines1.
Our hESC lines are listed in the USA’s National Institute of Health registry (http://escr.nih.gov/ under ES Cell International) and qualify for research that is federally funded.
B. Development of differentiated cells
The utilization of hESCs in transplantation therapy depends on the capability of the stem cells to differentiate in culture into more specialized cells that make up the human body. Our group documented for the first time that under specific culture conditions, hESCs could be induced to differentiate into a mixture of mature cells including muscle and nerve cells1.
For cell based therapies and scientific research, the development of cultures enriched for one cell type rather then a mixture of various cells is required. We were the first (with an American group publishing simultaneously in the same issue of the journal) to develop methods that allow the derivation of near homogenous populations of developmentally-competent proliferating immature nerve cells (neural precursors). Following transplantation to the brain of newborn mice, the neural precursors responded to host brain cues and signals, migrated extensively, participated in the processes of host brain development, and could construct nerve lineages2.
The neural precursors that we have developed from hESCs may pave the way for the development of more specialized nerve cells for the treatment of various neurologic disorders such as Parkinson’s disease or multiple sclerosis. Indeed, with regard to Parkinson’s disease, we have recently shown for the first time that transplantation of hESC-derived neural precursor cells induces functional recovery in an animal model of the disease11.
C. Genetic modification of hESCs
Genetic modification of hESCs may have broad applications in basic scientific research and cell-based therapies. We have recently reported on the development of a highly effective method for stable genetic modification of hESCs by viral vectors3.
Our scientific accomplishments and contribution to the field are well recognized worldwide. We have authored or co-authored nine papers that were published in distinguished scientific journals 1-9. Our significant contribution to the field was recently reviewed in an editorial article in the prestigious journal Science10.
The Center’s Research Activity
To accomplish the key goal of the center, we are focusing on promoting the developments that are essential to exploit the clinical potential of hESCs:
A. Development of hESCs in quality and sufficient quantity for transplantation and therapy
The existing hESC lines worldwide, were developed for research purposes and are probably not suitable for clinical transplantation. These cell lines have not been established under the appropriate quality assurance conditions.
A second problem is that the cells have been derived and cultivated on mouse embryonic fibroblasts and therefore potentially may transfer mouse pathogens to human recipients. In a collaborative research effort with the Department of Gynecology, we have initiated efforts to develop new, animal product free cell lines that will be suitable for clinical transplantation.
Hadassah is an ideal center for this purpose since it comprises a large IVF facility as a source of embryos, a hESC research center, and a Current Good Manufacturing Production (cGMP) facility designed for the development of products for clinical trials. The Israeli Ministry of Health Supreme Ethical Committee approved the development of new hESC lines eligible for transplantation therapy, at Hadassah.
In addition to the derivation of new cell lines, we need also to focus on the development of the technology that will allow the culture of hESCs in bulk. At present hESCs are propagated at a low scale, most commonly on a layer of supportive feeder cells. To exploit their potential we have to develop culture systems that will not depend on the feeders and will facilitate the generation of large quantities of pure stem cell populations.
B. Derivation of pure cultures of mature functional cells for transplantation
Human ES cells differentiate in culture into a mixture of various types of mature cells. To allow the utilization of hESCs for transplantation, directing the process of differentiation into a pure culture of a single cell type such as cardiac cell, insulin producing cell or neuron is required.
At present, our program is mainly focusing, in collaboration with the department of Endocrinology and Neurology, on the development of hESC derived progeny for transplantation in diabetes mellitus and Parkinson’s disease, for the following reasons.
The two illnesses are extremely common with 120 millions patients world-wide suffering from diabetes, and over one million patients in the USA with Parkinson’s disease.
Both disorders result from the degeneration and death of a specific type of cell, the insulin producing cells in diabetes and a discrete cluster of brain cells known as dopaminergic neurons in Parkinson’s disease.
In both conditions there is proof of clinical therapeutic benefit following cell transplantation and replenishment of the patients’ degenerated cells.
Limited availability of cells for transplantation is the major obstacle for widespread use of cell therapy in these disorders, while hESCs may serve as an unlimited donor source of dopaminergic neurons and insulin producing cells to treat these disorders.
In the area of cell transplantation for neurological conditions, we are also focusing in collaboration with the department of Neurology on the development of hESC based therapy for multiple sclerosis (MS). Multiple sclerosis is a common cause of chronic neurological disability in the young population, affecting primarily women.
In this condition the patient's own immune system attacks oligodendrocytes, which are the specialized cells that produce myelin sheaths for the nerves in the brain. Without myelin, the nerves are unable to transmit information efficiently and eventually degenerate, leading to irreversible disabilities, such as paralysis, blindness and incontinence.
Current treatment in MS is primarily directed at inhibiting or modulating the injurious immune attack. However, state of the art therapy is unable to alter the natural course of disease in most cases. It has been shown that stem cell transplantation can improve the clinical symptoms of experimental animal models of MS.
We are therefore examining the effect of transplantation of hESC-derived neural precursors and oligodendrocyte in these models. Initial data are encouraging and show that grafted neural precursors migrate towards the inflamed brain areas and survive in the brain for prolonged periods of time. We are evaluating now whether the transplanted cells ameliorate the clinical signs of the experimental disease.
Our program includes also the development of hESC derived mature cells for the potential treatment of several other conditions such as retinal degeneration, familial dysotonomia, and liver failure.
C. The development of genetically modified hES cells for gene therapy.
A key obstacle in the implementation of gene therapy treatments is the need to develop an efficient vehicle that will carry and express genes of interest in target organs. Genetically modified transplanted hESCs may serve as vectors for the transfer and expression of genes in target organs. We are developing methods for genetic modification of hESCs and recently reported our results with lentiviral vectors3. We have demonstrated the potential of genetically modified hESCs to express transgenes after transplantation. We are now studying the clinical effect of transplanted genetically modified hESCs in animal models of neurological disorders.
D. Coping with the potential problem of immune rejection
The grafting of mature cells or tissues between two genetically unrelated individuals almost invariably results in graft rejection. It is possible that grafting of hESC- derived mature progeny will also induce rejection. We are studying the immune response that is provoked by hESCs as the basis for the development of strategies to avoid immunological rejection of hESC-derived tissues.
In addition we have recently established a somatic cell nuclear transfer system in the mouse model, as a basis for future potential application with human oocytes. The transfer of a patient’s somatic nucleus into a donated oocyte may facilitate the production of ES cells genetically identical to the patient and will allow autologus transplantation of differentiated progeny from these cells without rejection.
This system will also allow the generation of hESC lines after the transfer of somatic nuclei from patients with various disorders. These cell lines will serve as an ideal model to study in culture the pathogenesis of the disorders of the patients from which they have been derived, and will be an invaluable tool for the development of new drugs to treat these conditions.
References
1. Reubinoff BE Pera MF, Fong CY, Trounson A, Bongso A. Embryonic stem cell lines from human blastocysts: somatic differentiation in vitro. Nature Biotechnol 2000; 18: 399-405.
2. Reubinoff BE, Itsykson P, Turetsky T, Pera MF, Reinhartz E, Itzik A, Ben-Hur T. Neural progenitors from human embryonic stem cells. Nat Biotechnol 2001; 19: 1134-1140.
3. Gropp M, Itsykson P, Singer O, Ben-Hur T, Reinhartz E, Galun E, Reubinoff BE. Stable genetic modification of human embryonic stem cells by lentiviral vectors. Molecular Therapy 2003; 7: 281-287.
4. Drukker M, Katz G, Urbach A, Schuldiner M, Markel G, Itskovitz-Eldor J, Reubinoff B, Mandelboim O, Benvenisty N. Characterization of the expression of MHC proteins in human embryonic stem cells. Proc Natl Acad Sci USA 2002; 99: 9864-9869.
5. Goldstein RS, Drukker M, Reubinoff BE, Benvenisty N. Integration and differentiation of human embryonic stem cells transplanted to the chick embryo. Developmental Dynamics 2002; 225: 80-86.
6. Cooper S, Bennett W, Andrade J, Reubinoff BE, Thomson J, Pera MF. Biochemical properties of a keratan sulphate/chondroitin sulphate proteoglycan expressed in primate pluripotent stem cells. J Anat 2002; 200(Pt 3): 259-265.
7. Pera MF, Andrade J, Houssami S, Reubinoff BE, Trounson A, Stanley EG, Ward-van Oostwaard D, Mummery C. Regulation of human embryonic stem cell differentiation by BMP-2 and its antagonist noggin. J Cell Sci. 2004;117:1269-1280.
8. Reubinoff BE, Pera M, Vajta G, Trounson AO. Effective cryopreservation of human embryonic stem cells by the open pulled straw (OPS) vitrification method. Human Reproduction 2001; 16: 2187-2194.
9. Pera MF, Reubinoff BE, Trounson A. Human embryonic stem cells. J Cell Science 2000;113: 5-10.
10 Vogel G. Stem cells. In the Mideast, pushing back the stem cell frontier. Science 2002; 295: 1818-1820.
11. Ben-Hur T, Idelson M, Khaner H, Pera M, Reinhartz E, Itzik A, and Reubinoff BE. Human embryonic stem cell-derived neural progenitors correct behavioral deficits in a Parkinson rat model. Stem Cells 2004; 22(7):1246-1255. |