BIOCHEMICAL-EVIDENCE FOR AUTOCRINE PARACRINE REGULATION OF APOPTOSIS IN CULTURED UTERINE EPITHELIAL-CELLS DURING MOUSE EMBRYO IMPLANTATION IN-VITRO/

During embryo implantation, apoptosis is observed morphologically at t he implantation site of endometrium. The objectives of this study were to demonstrate biochemical evidence of apoptosis and quantitative ass essment of DNA fragmentation in uterine epithelial cells using a mouse implantation model, and to investigate the autocrine/paracrine regula tion of apoptosis in uterine epithelial cells during blastocyst outgro wth. Blastocysts from day 4 pregnant mice were cultured on uterine epi thelial cells for 96 h. Uterine epithelial cells dislodged by trophobl asts in endometrium-trophoblast unit demonstrated morphological featur es of apoptosis by Acridine Orange staining. Electrophoresis demonstra ted DNA ladder and DNA fragmentation by enzyme-linked immunosorbent as say markedly increased after 48 h period of incubation. Apoptosis incr eased in an exponential way in accordance with trophoblast outgrowth. In addition, DNA fragmentation was shown in the epithelial cells by ad ding embryo-conditioned medium (CM) and the effect of embryo CM on apo ptosis was significantly inhibited by anti-transforming growth factor (TGF)-beta antibody. Delayed outgrowth was observed after 48 h of incu bation in the blastocysts cultured with anti-TGF-beta antibody. These results suggest there is autocrine/paracrine regulation of apoptosis i n uterine epithelial cells at mouse embryo implantation and that TGF-b eta might play an important role in the occurrence of apoptosis in the endometrium-trophoblast unit.