Morphological, Histological and Immunohistochemical Study of the Rabbit Uterus during Pseudopregnancy

Abstract

Ten mature virgin rabbit does (4-5 months old) with mean weight of 2.4 kg were induced to ovulate; by intramuscular injection of HCG (50-70 IU). The day of induction was considered 0 days. Uteri were obtained from 14 h, 3, 7, 18 days post induction. At first stage of pseudopregnancy; the two uteri became hyperemic and slightly swollen. The uterine epithelium and endometrial glands epithelium were of columnar type with oval basal nuclei. The endometrial glands were few in number and small in size. The endometrial glands showed apocrine activity. The uterus had six longitudinal folds and the uterine epithelium form crypts. The endometrium had slight vascularization. At middle stage of pseudopregnancy, the two uteri became hyperemic and more swollen. This stage characterized by; mucosal folding, glandular formation, epithelial proliferation and thickening of the uterine wall. At last stage of pseudopregnancy; the two uteri became flaccid and more swollen. This stage characterized by dramatic changes in the uterine architecture in the form of: increased epithelial proliferation and crypt formation increase the complexity of luminal folding, increase in length, size and abundance of the uterine endometrial glands, increase in the uterine micro vascular development (increased abundance of the large microvessels and development of subepithelial capillary plexuses). Tunica vascularis could be demonstrated between the inner circular and outer longitudinal smooth muscle fibers of the myometrium at the all stages of psedopregnancy. Telocytes with its characteristic morphology could be demonstrated in the myometrium of the rabbit uterus during pseudopregnancy. Cell-specific immuno-localization of progesterone receptors alpha (PRA) in the rabbit uterus during pseudopregnancy revealed that, there were mild, moderate and strong nuclear PRA immunostaining in the endometrial epithelial cells, endometrial glands and in the smooth muscles fibers of the myometrium of the first, middle and last stages of pseudopregnancy respectively. The present study revealed that the morphological, histological and immunohistochemical changes in the rabbit uterus during pseudopregnancy resembled that occurred during early stage of pregnancy. These changes were characterized by dramatic changes in the uterine architecture in the form of: increased epithelial proliferation and crypt formation increase the complexity of luminal folding, increase in length, size and abundance of the uterine endometrial glands, increase in the uterine microvascular development. These uterine changes were accompanied with PRA immunolocalization in the uterine tissues.