Involvement of apoptosis during deciduomal regression in pseudopregnant hamsters - Effect of progesterone

We determined whether fragmentation of genomic DNA, apoptosis, occurs durin g deciduomal regression in pseudopregnant hamsters and the effect of proges terone on the apoptotic processes. Artificially induced deciduoma were obta ined on different days of pseudopregnancy and separated into mesometrial an d antimesometrial tissues. The deciduomal cell cycle progression and popula tion profiles of both sides were compared by flow cytometry. The proportion of sub-G(1) peak, which was correlated with the apoptotic cells, were abou t 10% on day 8 and reached to 40% in both tissues on day 10. Exogenous prog esterone treatment by daily injection (2 mg; s.c.) on and after day 8 reduc ed the percentage of low molecular weight DNA in both tissues on day 10 and day 12 as compared to the nontreated control one, respectively. The appear ance of DNA ladder was also delayed at least 24 h by progesterone administr ation. The intensity of DNA fragmentation was more pronounced in antimesome trial deciduoma. In situ 3'-end labeling of apoptotic cells further substan tiated the apoptotic process. The apoptotic cells first appeared in the lum inal region in antimesometrial deciduoma on day 8 and spreaded all over the entire deciduomal tissue on day 10. Progesterone treatment stimulated deci duomal proliferating cell nuclear antigen (PCNA) expression, maintained dec iduoma until day 14 and retarded the differentiation and regeneration of th e uterine epithelium. (C) 2001 Elsevier Science Inc. All rights reserved.