GRANULOSA CELLS APOPTOSIS PREDISPOSES TO FOLLICULAR ATRESIA.
In the cow, as known, up to 80 Follicles in 2-3 Waves of folliculogenesis go into atresia in one estrous cycle. Before atresia, membrana granulosa and thecal cells enter into apoptosis or what is called programmed cell death, cell falling or suicide. Events leading to apoptosis are centered on hormonal, growth peptide factors and apoptosis inducers. These inducers require membrane receptor interaction, activalion 01 caspases, PARP( a DNA repair enzyme) cleaved by caspase and PS (phosphatidyle serine) externalization. These events result in DNA fragmentation (laddering) or repair predisposing to cancer, plasma membrane asymmetry and leakage. This is important for macrophage recognition of apoptotic cell. Moreover, mitochondria swell up and rupture with resultant cell shrinkage. Apoptosis differs from necrosis which is due to exposure of the cell to toxic or physical agents in that during necrosis cells swell up, lyse or burst with release of cytotoxins. Diagnosis of apoptosis includes determination of changes in nuclear DNA (DNA index) of the cells using flow-cytometry, Annexin -V- conjugate to detect membrane apoptosis either using fluorescence or using flow cytometry while detection of DNA laddering is done using fluorescent microscopy or flow-cytometry.