The process of apoptosis in follicular epithelial cells in the rabbit ovary, with special reference to involvement by macrophages.

Using rabbit ovaries, this study investigated the fate of follicular epithelial cells undergoing apoptosis in follicle atresia, especially in atretic Graafian follicles. This is the first report to apply the TUNEL method and histochemistry for acid phosphatase in order to demonstrate macrophages immigrating into the follicles to eliminate the apoptotically dead epithelial cells. At initial stages of atresia, a few epithelial cells solitarily revealed the condensation of nuclear chromatin characteristic of apoptosis, simultaneously reacting positive to the TUNEL method. At advanced stages, chromatin condensation and separation as well as cytoplasmic fragmentation spread to the entire follicular epithelium. In such an advanced atretic follicle, large round cells appeared in the follicular lumen; these could be identified as macrophages by their morphologies and positive reactions for acid phosphatase. These macrophages were adhering to and internalizing apoptotic epithelial cells and their fragments until the lumen became completely free of dead cells and fragments.