333 GENERATION OF OOCYTE-LIKE STRUCTURE FROM OVARIAN SURFACE EPITHELIAL STEM CELLS OF GOAT

Abstract

Stem cells have potential for therapeutic application. Continuous repair of ovarian surface epithelium following folliculogenesis and ovarian carcinoma suggests the presence of stem cells in ovarian epithelial cells. In vitro gametogenesis in livestock will result in large numbers of oocytes production from a single ovary, resulting in faster multiplication of superior germplasm of livestock species, treatment of infertile animals, and conservation of endangered species. The present study was conducted with the objective of in vitro differentiation of putative ovarian surface epithelial stem cells into oocyte-like structures in goat model. Ovary samples of 1- to 2-year-old goats were collected from slaughterhouse. The surface of the ovary was gently scraped using sterile blunt scraper to isolate ovarian surface epithelial stem cells. These scraped cells were cultured in DMEM/F12 supplemented with 20% FBS for 3 weeks in 5% CO₂ at 37°C with maximum humidity_. The cultured stem cells were characterised for stemness by RT-PCR and immunostaining for Oct4, Sox2, and Nanog genes after 3 weeks. These putative stem cells were in vitro differentiated spontaneously to oocyte-like structures in DMEM/F12 medium and characterised for premeiotic markers by RT-PCR and immunostaining for VASA, DAZL, and STELLA genes. Results of this study provide evidence for the presence of putative stem cells with pluripotent characteristics in the ovarian surface epithelium. The cultured cells were found to be round in shape, with a high nucleus to cytoplasm ratio under inverted microscope, and found positive for stem cell markers of Oct4, Sox2, and Nanog genes. A total of 66 oocyte-like structures were produced from 12 ovaries. These oocyte-like structures were nearly similar to oocytes produced in vivo, both morphologically and in molecular gene expression. The oocyte-like structures were also found positive for premeiotic markers of VASA, DAZL, and STELLA genes by RT-PCR and immunostaining. From this study, we concluded that the ovarian surface epithelial cells have putative stem cells which can be in vitro differentiated into oocyte-like structures in goat. These oocyte-like structures need further characterisation of their surface membrane, more molecular markers, and following their developmental potential. These oocytes can help for multiplication of elite germplasm, curing infertile animals, and saving endangered species.