Hormonal regulation of apoptosis in the endometrium of common marmosets (Callithrix jacchus)

Phase-dependent apoptotic changes in the human endometrium during an ovarian cycle imply a potential role of steroids in the regulation of apoptosis. The present study was undertaken to determine the direct role of hormones in endometrial apoptosis in marmosets (Callithrix jacchus), a primate species which shows similarity to humans in terms of the cycle length and pattern. Endometrial apoptosis was detected by 3'-end labeling (TUNEL) in various phases of ovarian cycle in naturally cycling healthy marmosets (n=14) and also in ovariectomized marmosets (n=13) treated with either estradiol alone (E) or progesterone alone (P) or estradiol followed by progesterone (E+P). Expressions of apoptosis associated genes such as Bcl-2 family members (Bax and Bcl-2), proliferating cell nuclear antigen (PCNA)--a proliferation marker and steroid receptors, ERalpha and PR A were analysed by immunohistochemical methods. Apoptosis was intense in the glandular epithelial cells of endometrium during the mid-luteal phase as compared to other phases in naturally cycling animals; in the E+P group as compared to other groups of ovariectomized animals (P<0.05). Pronounced apoptosis in the mid-luteal phase was accompanied by the increased expression of Bax in glandular epithelial cells; while Bcl-2 immunoreactivity remained unchanged. PCNA expression was higher in the naturally cycling animals in the follicular phase and in the E group of the ovariectomized animals as compared those in the other groups. Immunoreactive ERalpha and PR A in glandular epithelial cells were most abundant during early follicular phase in naturally cycling animals and in both E and E+P groups among the ovariectomized animals. The present study highlights the importance of apoptosis in endometrial remodeling during the ovarian cycle and secondly, the role of both estradiol and progesterone in the regulation of apoptosis.