Studies On Cell Apoptosis Of Porcine Fetal Ovary At Early Stage

Apoptosis plays an important role in the development of multicellular organism and normal cellular regeneration,as well as in keeping the tissues in normal structure and function.It could keep the organs,tissues and cells in balance through eliminating unneccesary,useless,abnormally-developed and harmful cells,or those which had accomplished their missions.Oogenesis is an important physiological event in the process of embryonic development.Under physical conditions,not all the oogonium/oocytes could develope to meiophase and most of them unergo atresia and degeneration afer apoptosis. Even those oocytes that initiate their meiosis would go apoptosis in developping follicle (atresia) in a relative large amount.For porcine oogenesis,33-61 days after gestation was a pivotal period.And in order to elucidate apoptosis change and its charicteristics in oocytes and granulosa cells,the ovaries of porcine fetuses were studied in the present study and the fluorescent staining was utilized to invesigate apoptosis of oogoniums and granulosa cells during the period.The localization of Bax and Bcl-2,two key proteins involved in apoptosis,was examined by immunohistochemical assay.The results showed that:â‘ The apoptosis of oogoniums and primordial germ cells was found in the ovary of porcine fetus since 33 days of gestation.As the gestation went on, the apoptosis rate of oogonium increasd,and it was 3.13%,4.32%,5.50%,9.43%and 11.10%respectively at 33th,40th,47th,54th and 61st d of gestation And the apoptosis rate of granulosa cells was 8.89%,12.45%,14.74%,17.96%and 22.81%respectively.â‘¡The positive staining for Bax was detected in epithelial cells,oocyte,oogonium,vascular epithelial cells,necrotic oocyte and oogonium.There was heavy staining at 54th day of gestation.Degenerated oogonium and oocyte showed strong staining for Bax and the cytoplasm was heavily stained.Bcl-2 was localized in epithelial cells,oocyte,oogonium, vascular epithelial cells,necrotic oocyte and oogonium,and cytoplasma of these cells was yellow or brown-yellow under microscope.There was heavy staining at the 61th day of gestation.Degenerated oocyte and oogonium had strong expression of Bax and cytoplasm was heavily stained,especially in symplasm.The results indicate that apoptosis of oogonium and granulosa cells happens and increases at the early stage of porcine fetus ovary.In this process,Bax and Bcl-2 are expressed in the porcine fetus ovary.They may be corrdinated in the adjustment of apoptosis of ovarian cells.Such findings might be the indications for further understanding of the oogenesis.