The Role of Proteins in Apoptosis of Somatic and Germ Cells in the Mouse Ovary

In this study, to determine the mechanisms of cell death in developing follicles, we investigated whether expression of Bcl-2, p53 and Bax play a role throughout the growth of follicles in the mice. Ovarian tissues and oocytes were obtained from 30 Mus Musculus type mouse. The immunostaining of ovarian tissue sections and oocytes was performed using anti-Bcl-2, anti-Bax and anti-p53 antibodies and terminal deoxynucleotidyl transfrase (TdT) assay (TUNEL) were also used for detection of internucleosomal DNA fragmentation. In ovarian tissue section evaluation, granulosa cells in antrum of secondary and Graaf follicles were positive with TUNEL staining. Immunoreactivity of Bcl-2 was moderate in primary and secondary follicles of granulosa cells. While immunostaining of p53 was moderate in granulosa cells of Graaf follicles, Bax immunoreactivity was moderate and strong in secondary and Graaf follicles, respectively. When granulosa cells were break off from zona pellucida, there were TUNEL positive cells. In unfertilised oocytes evaluation, TUNEL positive cells were observed in the granulosa cells which were free from zona pellucida. When the granulosa cells were attached with zona pellucida, they were TUNEL negative. While immunoreactivity of Bcl-2 was detected in both oocytes and granulosa cells which were attached with zona pellucida, immunostaining of p53 were only detected in granulosa cells which break off from zona pellucida. In conclusion, regulation of apoptosis in granulosa cells may be controlled by Bax expression and when the granulosa cells were not attached with zona pellucida, they may go into the apoptotic cascade. Therefore; we suggest that, the death of granulosa cells may control signals from intrinsic pathways in the Graaf follicule or from extrinsic pathways after ovulation. However, we consider of further studies to be necessary.