Reconstitution of Spermatogenesis from Testis Failure after Spermatogonial Stem Cells (Ssc) Transplantation for Male Fertility Preservation-A Transgenic Mouse Model

The production of functional male gametes is dependent on the continuous activity of germline stem cells－spermatogonial stem cells (SSCs). SSCs self-renew and produce large numbers of differentiating germ cells that become spermatozoa throughout postnatal life and transmit genetic information to the next generation. The availability of a transplantation assay system to unequivocally identify male germline stem cells has allowed them in vitro culture, cryopreservation, and genetic modification. Moreover, the system has enabled the identification of conditions and factors involved in stem cell self-renewal, the foundation of spermatogenesis, and the production of spermatozoa. The increased knowledge about these cells is also of great potential practical value, for example, for the possible cryopreservation of stem cells from boys undergoing treatment for cancer to safeguard their germ line. The aim of this research allowed SSCs in vitro culture, cryopreservation and restored fertility by transplantation assay system. Aim 1: The concentration of SSCs in the adult mouse testis is only 1 in 3,000–4,000 cells, and no morphologic or biochemical markers exist for the stem cells. Using the surface -antigenic profile of mouse SSCs, which is MHC class I- Thy-1lo/+ c-Kit- αv-integrin-/dim α6-integrin+, a highly enriched SSC population could be obtained. Aim 2: Successful cryopreservation and culture of SSCs is an important factor in guaranteeing the fertility preservation by SSCs transplantation. The aim is to evaluate the effects of varied cryopreservation and culture on SSCs survival and function. We aim to find optimal methods for cryopreservation and culture of SSCs from a fertile male mouse. Aim 3: Evaluate the effects of donor SSCs from a fertile adult or newborn mouse (FVB/N-Tg PolII-luc) and then transplanted to the seminiferous tubules of an infertile adult male mouse (FVB/N) on re-establish spermatogenesis and restore fertility. The transplantation assay system has been used to study the biology of SSCs, which made possible the identification of external factors that support in vitro self-renewal and proliferation of mouse SSCs.