PROGESTERONE WITHDRAWAL AND RU-486 TREATMENT STIMULATE APOPTOSIS IN SPECIFIC UTERINE DECIDUAL CELLS

Progesterone secretion is required for the growth and differentiation of endometrial stromal cells to form decidual cells, For many cells wh ere a growth factor supports cell growth and proliferation, withdrawal of the growth factor initiates apoptosis. This study determined the t ime course and tissue location of apoptosis in deciduomal tissue after withdrawal of progesterone or injection of the antiprogestin, RU-486. Total DNA was isolated from decidual tissues at intervals after exper imental treatments and separated electrophoretically. internucleosomal DNA fragmentation characteristic of apoptosis was measured by quantit ating levels of the 200 bp fragment. Apoptotic cells in tissue section s were detected by direct immunoperoxidase detection of digoxigenin-la beled DNA. Decidual apoptosis reached maximal levels at 12h after with drawal of progesterone or injection of RU-486. Increased concentration s of apoptotic cells were observed at the periphery of the growing dec iduoma and in the antimesometrial deciduoma near the luminal epitheliu m after both treatments. These results suggest the withdrawal of proge stin initiates apoptosis in cells at the early stages of decidualizati on.