The research focus of the Department is primarily on pluripotent stem cells and their applications in reproductive biology and regenerative medicine. The other major research focus of the group is on fertility issues of cancer patients/survivors.
Embryonic stem cells
Two human embryonic stem cell lines (KIND1 and KIND2) derived on human feeders are available with our Department and they have recently also been adapted to feeder-free state. Feeder fibroblasts were found to differentiate into myofibroblasts to support continuous proliferation of embryonic stem cells in vitro. Both cell lines have good propensity to differentiate into mesoderm and endoderm. These cell lines have been differentiated into tripotent cardiac and pancreatic progenitors. Studies are ongoing to delineate epigenetic status of ES cells during their differentiation into various lineages. Procedures to generate autologous human embryonic stem cell lines by somatic cell nuclear transfer (SCNT) have been standardized using sheep eggs. Further establishment of these technologies in humans is not felt necessary any longer since pluripotent stem cells (see below) exist in various adult body organs.
Very small embryonic-like stem cells (VSELs)
Novel pluripotent stem cells termed very small embryonic-like stem cells (VSELs) in cord blood, adult testis and ovary and pancreas have been detected in our laboratory. Being quiescent by nature- VSELs persist in the mouse gonads after treatment with busulphan and cyclophosphamide and may be later targeted to regenerate the chemoablated gonads and thereby restore fertility. Recently we also reported that VSELs are implicated during pancreas regeneration after partial pancreatectomy in mice.
The ovarian cortical tissue pieces (besides being a source of primordial follicles) are a good source of stem cells in vitro. These stem cells during spontaneous differentiation into oocyte-like structures exhibit presence of germ cell nests, Balbiani body and cyclosis– processes that are well studied during fetal ovarian development. Also PMSG treatment to adult mice results in augmented neo-oogenesis and follicular assembly.
Novel action of FSH on VSELs
FSH receptors (FSHR) expression on the VSELs present in both adult mammalian ovary and testis has been observed by our group. Besides the well-known action of FSH on granulosa cells in ovary and Sertoli cells in testis, VSELs are stimulated by FSH, undergo self-renewal followed by differentiation (gametogenesis). Interesting this action is mediated through a novel FSHR transcript termed FSHR3 which has a putative exon 11 and lacks exon 10.
Thus besides showing presence of stem cells in adult ovary – our group has also provided the mechanism whereby the stem cells are involved in neo-oogenesis and follicle assembly in adult ovary. This is newly emerging understanding against the existing concepts that ovary has fixed number of eggs at birth and initial follicle growth is independent of FSH. We also recently put forth a hypothesis to explain why mutations in FSHR have not yet been reported world-wide in cases of pre-mature ovarian failure and cancers. We have also provided stem cell basis for menopause and ovarian cancer (http://www.ncbi.nlm.nih.gov/pubmed/25269615).
Better potential of VSELs compared to ES/iPS cells for regenerative medicine
Several groups across the world are attempting to make gametes from pluripotent stem cells (embryonic or induced pluripotent) but the field is stuck at the step to convert these stem cells into primordial germ cells (PGCs). Thus the aim to obtain synthetic gametes from stem cells still remains a distant dream. We have observed that VSELs have the ability to spontaneously differentiate into gametes and thus are best option to obtain ‘synthetic gametes’. The reason for better ability of VSELs to spontaneously form gametes is because they are indeed PGCs which survive in adult tissues (http://www.ncbi.nlm.nih.gov/pubmed/25421462).
Compared to ES/iPS cells which give rise to their fetal counterparts, VSELs show the ability to regenerate both acinar cells and islets in adult mouse pancreas.