Apoptosis in the uterus of mice with pregnancy loss

PROBLEM: The mechanisms mediating pregnancy loss induced by various agents are far from being understood. Thus, we investigated the possible involvement of one such mechanism, the apoptotic process, in pregnancy loss induced by lipopolysaccharide (LPS) or cyclophosphamide (CP) as well as the associated changes in the apoptosis-regulating gene products p53 and bcl-2. METHOD OF STUDY: Pregnancy loss was induced by LPS or CP on days 9 or 12 of pregnancy, respectively. LPS- or CP-associated apoptosis was assessed by the TdT mediated dUTP-biotin nick end labeling (TUNEL) method as well as by DNA fragmentation analysis, while p53 or bcl-2 expression was evaluated by immunohistochemistry. RESULTS: Lipopolysaccharide treatment initiated a resorption process that was accompanied by the appearance of apoptotic cells in the uterus, which increased in number by 24 hr after treatment. Induction of pregnancy loss with CP resulted in the appearance of some apoptotic cells in the uterus, reaching a peak at 72 hr after treatment. DNA fragmentation analysis revealed a DNA ladder at 24 hr after LPS as well as 72 hr after CP treatment. Immunohistochemical analysis demonstrated a continuous p53 expression in the uterus of LPS- or CP-treated mice, which was somewhat elevated at the peak of the apoptotic process. On the other hand, bcl-2 expression in LPS-treated mice could be reciprocally correlated with the apoptotic process, appearing only at its initiation or completion, while in CP-treated mice it was continuously expressed except for some elevation at the completion of the apoptotic process. CONCLUSIONS: Our results suggest a possible role for the apoptotic process in mechanisms mediating pregnancy loss and indicate an involvement of p53 and bcl-2 in its regulation.