Center for Stem Cell Research

Petah Tikva, Israel

Center for Stem Cell Research

Petah Tikva, Israel
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Sugimura R.,Stowers Institute for Medical Research | He X.C.,Stowers Institute for Medical Research | Venkatraman A.,Stowers Institute for Medical Research | Venkatraman A.,Center for Stem Cell Research | And 9 more authors.
Cell | Year: 2012

Wnt signaling is involved in self-renewal and maintenance of hematopoietic stem cells (HSCs); however, the particular role of noncanonical Wnt signaling in regulating HSCs in vivo is largely unknown. Here, we show Flamingo (Fmi) and Frizzled (Fz) 8, members of noncanonical Wnt signaling, both express in and functionally maintain quiescent long-term HSCs. Fmi regulates Fz8 distribution at the interface between HSCs and N-cadherin+ osteoblasts (N-cad +OBs that enrich osteoprogenitors) in the niche. We further found that N-cad+OBs predominantly express noncanonical Wnt ligands and inhibitors of canonical Wnt signaling under homeostasis. Under stress, noncanonical Wnt signaling is attenuated and canonical Wnt signaling is enhanced in activation of HSCs. Mechanistically, noncanonical Wnt signaling mediated by Fz8 suppresses the Ca2+-NFAT- IFNγ pathway, directly or indirectly through the CDC42-CK1α complex and also antagonizes canonical Wnt signaling in HSCs. Taken together, our findings demonstrate that noncanonical Wnt signaling maintains quiescent long-term HSCs through Fmi and Fz8 interaction in the niche. © 2012 Elsevier Inc.

Nambiar A.,Center for Stem Cell Research
Indian journal of medical ethics | Year: 2012

For consent in biomedical research, it is essential that research participants understand the need for research, the study protocol, the risk and benefits of participation, the freedom to participate or decline and the right to leave the study at any time. A structured questionnaire was used to assess understanding and knowledge among nursing trainees participating in a cohort study investigating exposure and latent tuberculosis at a tertiary care hospital. Data were collected for 138 participants. While 97% were aware of their enrollment into a research protocol, only 78% could state that it was a study on tuberculosis. Approximately two-thirds were aware of plans for blood collection, but not all of them knew the timings or number of samples. The majority (59%) participants had consulted others before making the decision to participate, and only 73% felt that their participation was completely voluntary. Even among healthcare trainees, emphasis needs to be placed on testing both the knowledge and understanding of participants to ensure the principle and practice of truly informed consent.

Selot R.S.,Center for Stem Cell Research | Hareendran S.,Center for Stem Cell Research | Jayandharan G.R.,Center for Stem Cell Research | Jayandharan G.R.,Christian Medical College
Current Pharmaceutical Biotechnology | Year: 2014

Gene therapy has become a clinical reality as demonstrated by remarkable benefits seen in Phase I/II clinical trials for hemophilia B, lipoprotein lipase deficiency and Leber's congenital amarousis. The choice of, and the improved understanding in vector characteristics have contributed significantly to this success. The adeno-associated virus (AAV) vectors used in these trials have been long known to be relatively safe and efficacious. However, certain factors, most notably host immunity to the vector, prevent their widespread use. In patients who have pre-existing antibodies to AAV, these vectors will be rapidly cleared. Administration of a relatively high initial dose of vector to achieve and sustain a higher margin of therapeutic benefit is limited by concerns of vector dose-dependent T cell response. Frequent vector administration necessitated by the non-integrating nature of the virus is difficult due to the variable, yet significant host immunological memory. Thus generation of AAV vectors that are immunologically inert is pivotal for the long-term success with this promising vector system. Several strategies, that aim targeted disruption of antigenic sites or those that chemically modify the vectors have been proposed for host immune evasion. While these approaches have been successful in the pre-clinical model systems, this continues to be a field of intense experimentation and constant improvisation due to limited information available on vector immunology or data from human studies. This review forms a comprehensive report on current strategies available to generate immunologically inert AAV vectors and their potential in mediating longterm gene transfer. © 2013 Bentham Science Publishers.

Kaminitz A.,Center for Stem Cell Research | Mizrahi K.,Center for Stem Cell Research | Askenasy N.,Center for Stem Cell Research
Autoimmunity | Year: 2014

Immune profiling of non-obese diabetic (NOD) is a widely employed tool to assess the mechanisms of inflammatory insulitis. Our analysis of the female NOD colony revealed similar distribution of lymphoid lineages to wild type mice, and at various ages of prediabetic and diabetic mice. The profiles of mesenteric and pancreatic lymph nodes differ and often change reciprocally due to directed migration of T cells towards the site of inflammation. Significant events in our colony include early decline in CD4+CD25+CD62L + Treg, accompanied by gradual increase in CD4+CD25 +FoxP3+ Treg in peripheral lymphoid organs and pancreatic infiltrates. Impressively, aged euglycemic mice display significant transient rise in CD4+CD25-FoxP3+ Treg in the thymus, pancreas and draining lymph nodes. A significant difference was superior viability of effector and suppressor cells from new onset diabetics in the presence of high interleukin-2 (IL-2) concentrations in vitro as compared to cells of prediabetic mice. Overall, we found no correlation between FoxP3 + Treg in the pancreatic lymph nodes and the inflammatory scores of individual NOD mice. CD25-FoxP3+ Treg are markedly increased in the pancreatic infiltrates in late stages of inflammation, possibly an effort to counteract destructive insulitis. Considering extensive evidence that Treg in aged NOD mice are functionally sufficient, quantitative profiling evolves as an unreliable tool to assess mechanism and causes of inflammation under baseline conditions. Immune profiles are modulated by thymic output, cell migration, shedding of markers, proliferation, survival and in-situ evolution of regulatory cells. © 2014 Informa UK Ltd. All rights reserved.

Mizrahi K.,Center for Stem Cell Research | Askenasy N.,Center for Stem Cell Research
Blood | Year: 2014

Secretion of ligands of the tumor necrosis factor (TNF) superfamily is a conserved response of parenchymal tissues to injury and inflammation that commonly perpetuates elimination of dysfunctional cellular components by apoptosis. The same signals of tissue injury that induce apoptosis in somatic cells activate stem cells and initiate the process of tissue regeneration as a coupling mechanism of injury and recovery. Hematopoietic stem and progenitor cells upregulate the TNF family receptors under stress conditions and are transduced with trophic signals. The progeny gradually acquires sensitivity to receptor-mediated apoptosis along the differentiation process, which becomes the major mechanism of negative regulation of mature proliferating hematopoietic lineages and immune homeostasis. Receptor/ligand interactions of the TNF family are physiological mechanisms transducing the need for repair, which may be harnessed in pathological conditions and transplantation. Because these interactions are physiological mechanisms of injury, neutralization of these pathways has to be carefully considered in disorders that do not involve intrinsic aberrations of excessive susceptibility to apoptosis. © 2014 by The American Society of Hematology.

Hareendran S.,Center for Stem Cell Research | Balakrishnan B.,Christian Medical College | Sen D.,Christian Medical College | Kumar S.,Center for Stem Cell Research | And 4 more authors.
Reviews in Medical Virology | Year: 2013

SUMMARY: AAV-based gene transfer protocols have shown remarkable success when directed to immune-privileged sites such as for retinal disorders like Lebers congenital amaurosis. In contrast, AAV-mediated gene transfer into liver or muscle tissue for diseases such as hemophilia B, α1 anti-trypsin deficiency and muscular dystrophy has demonstrated a decline in gene transfer efficacy over time. It is now known that in humans, AAV triggers specific pathways that recruit immune sensors. These factors initiate an immediate reaction against either the viral capsid or the vector encoded protein as part of innate immune response or to produce a more specific adaptive response that generates immunological memory. The vector-transduced cells are then rapidly destroyed due to this immune activation. However, unlike other viral vectors, AAV is not immunogenic in murine models. Its immunogenicity becomes apparent only in large animal models and human subjects. Moreover, humans are natural hosts to AAV and exhibit a high seroprevalence against AAV vectors. This limits the widespread application of AAV vectors into patients with pre-existing neutralising antibodies or memory T cells. To address these issues, various strategies are being tested. Alternate serotype vectors (AAV1-10), efficient expression cassettes, specific tissue targeting, immune-suppression and engineered capsid variants are some approaches proposed to minimise this immune stimulation. In this review, we have summarised the nature of the immune response documented against AAV in various pre-clinical and clinical settings and have further discussed the strategies to evade them. © 2013 John Wiley & Sons, Ltd.

Balakrishnan B.,Christian Medical College | Jayandharan G.R.,Christian Medical College | Jayandharan G.R.,Center for Stem Cell Research
Current Gene Therapy | Year: 2014

Adeno-associated virus (AAV) based vectors have emerged as important tools for gene therapy in humans. The recent successes seen in Phase I/II clinical trials have also highlighted the issues related to the host and vector-related immune response that preclude the universal application of this promising vector system. A fundamental insight into the biological mechanisms by which AAV infects the host cell and a thorough understanding of the immediate and long-lived cellular responses to AAV infection is likely to offer clues and help design better intervention strategies to improve the therapeutic efficiency of AAV vectors. This article reviews the biology of AAV-host cellular interactions and outlines their application in the development of novel and improved AAV vector systems. © 2014 Bentham Science Publishers.

Sabapathy V.,Center for Stem Cell Research | Sundaram B.,Center for Stem Cell Research | Vm S.,Vellore Institute of Technology | Mankuzhy P.,Center for Stem Cell Research | Kumar S.,Center for Stem Cell Research
PLoS ONE | Year: 2014

Human mesenchymal stem cells (MSCs) are a promising candidate for cell-based transplantation and regenerative medicine therapies. Thus in the present study Wharton's Jelly Mesenchymal Stem Cells (WJ-MSCs) have been derived from extra embryonic umbilical cord matrix following removal of both arteries and vein. Also, to overcome the clinical limitations posed by fetal bovine serum (FBS) supplementation because of xenogeneic origin of FBS, usual FBS cell culture supplement has been replaced with human platelet lysate (HPL). Apart from general characteristic features of bone marrow-derived MSCs, wharton jelly-derived MSCs have the ability to maintain phenotypic attributes, cell growth kinetics, cell cycle pattern, in vitro multilineage differentiation plasticity, apoptotic pattern, normal karyotype-like intrinsic mesenchymal stem cell properties in long-term in vitro cultures. Moreover, the WJ-MSCs exhibited the in vitro multilineage differentiation capacity by giving rise to differentiated cells of not only mesodermal lineage but also to the cells of ectodermal and endodermal lineage. Also, WJ-MSC did not present any aberrant cell state upon in vivo transplantation in SCID mice and in vitro soft agar assays. The immunomodulatory potential assessed by gene expression levels of immunomodulatory factors upon exposure to inflammatory cytokines in the fetal WJ-MSCs was relatively higher compared to adult bone marrow-derived MSCs. WJMSCs seeded on decellularized amniotic membrane scaffold transplantation on the skin injury of SCID mice model demonstrates that combination of WJ-MSCs and decellularized amniotic membrane scaffold exhibited significantly better wound-healing capabilities, having reduced scar formation with hair growth and improved biomechanical properties of regenerated skin compared to WJ-MSCs alone. Further, our experimental data indicate that indocyanin green (ICG) at optimal concentration can be resourcefully used for labeling of stem cells and in vivo tracking by near infrared fluorescence non-invasive live cell imaging of labelled transplanted cells, thus proving its utility for therapeutic applications. © 2014 Sabapathy et al.

Jayandharan G.,Center for Stem Cell Research | Srivastava A.,Florida College | Srivastava A.,Center for Stem Cell Research
Seminars in Thrombosis and Hemostasis | Year: 2012

Despite significant advancements, state-of-the-art care remains inaccessible to patients with hemophilia, especially those from developing countries. Thus, innovative approaches in the management of this condition are needed to improve their quality of life. In this context, genetic studies in hemophilia have contributed to the better understanding of its biology, the detection of carriers, and prenatal diagnosis, and even fostering newer therapeutic strategies. This article reviews the applications of molecular genetics in hemophilia, in general, and how such techniques can be useful for optimizing patient care, in particular.© 2012 by Thieme Medical Publishers, Inc.

Mizrahi K.,Center for Stem Cell Research | Mizrahi K.,Tel Aviv University | Stein J.,Bone Marrow Transplant Unit | Yaniv I.,Tel Aviv University | And 2 more authors.
Stem Cells | Year: 2013

Tumor necrosis factor-α (TNF-α) has been suggested to exert detrimental effects on hematopoietic progenitor function that might limit the success of transplants. In this study, we assessed the influences of TNF-α and its two cognate receptors on the function of fresh umbilical cord blood (UCB) and cryopreserved mobilized peripheral blood (mPB). CD34+ progenitors from both sources are less susceptible to spontaneous apoptosis than lineage-committed cells and are not induced into apoptosis by TNF-α. Consequently, the activity of UCB-derived severe combined immune deficiency (SCID) reconstituting cells and long-term culture-initiating cells is unaffected by this cytokine. On the contrary, transient exposure of cells from both sources to TNF-α stimulates the activity of myeloid progenitors, which persists in vivo in UCB cell transplants. Progenitor stimulation is selectively mediated by TNF-R1 and involves activation of caspase-8, without redundant activity of TNF-R2. Despite significant differences between fresh UCB cells and cryopreserved mPB cells in susceptibility to apoptosis and time to activation, TNF-α is primarily involved in tropic signaling in hematopoietic progenitors from both sources. Cytokine-mediated tropism cautions against TNF-α neutralization under conditions of stress hematopoiesis and may be particularly beneficial in overcoming the limitations of UCB cell transplants. © AlphaMed Press.

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