Subtypes of active cell death in the granulosa of ovarian atretic follicles in the quail (Coturnix coturnix japonica)

Follicular atresia in the ovaries of Japanese quail was studied by cytochemistry and electron microscopy. Three different types of cell death coexisted in the granulosa. A large number of cells showed signs of apoptosis. The DNA fragmentation in these cells was demonstrated in a previous study using in situ end-labeling. A second and non-negligible type of cell death consisted of extensive autophagocytosis of the cytoplasm occurring simultaneously with late nuclear alterations. Finally, a few detached cells displayed cytoplasmic disintegration and small irregular clumps of chromatin condensation indicative of primary cell necrosis. Apoptotic versus autophagic cell death revealed a different pattern of acid phosphatase activity (lysosomal versus cytoplasmic). We propose that these observations may be linked to the existence of distinct subpopulations in the granulosa as has been shown by others. This study confirms the biochemical data on granulosa cell death, but demonstrates that apoptosis is not the exclusive mode of active cell death in follicular atresia.