Effect of Delayed Estrogen Replacement on Vaginal Histologic Composition in Rabbit

Ahn, Kyu Youn; Park, Kwangsung; Hwang, Eu Chang; Im, Chang Min; Kim, Cheul Su; Bae, Choon Sang

Abstract

PURPOSE
A decline in the circulating levels of estrogen impairs vaginal engorgement, which leads to histopathological changes in the vaginal tissues. The aim of this study was to evaluate the effect of delayed estrogen replacement on the vagina structure in castrated rabbits.
Materials and Methods
New Zealand White female rabbits were randomly divided into three groups; two groups (the castration and castration estrogen replacement groups) were castrated: the control group underwent sham operations. Nine weeks after surgery, the estrogen replacement group received subcutaneous injections of estrogen (50microgram/kg/day) for 4 weeks. Vaginal tissue was processed for histology with Masson's trichome stain. The expressions of e-NOS and n-NOS were examined by immunohistochemistry and Western blot.
RESULTS
From the histology, marked thinning of the vaginal epithelial layers, and decreased smooth muscle content and submucosal microvasculatures were evident, but with no increase in the collagen fibers in the castrated group was noted. The vaginal tissue of the estrogen replaced animal showed similar morphological features to those in the control rabbits. From the histomorphometry, the percentage of vaginal smooth muscle in the castrated group was significantly decreased compared to those in the control and estrogen replaced groups. The expression and signal intensity of e-NOS were decreased in the vagina of the castrated animals compare to those in the control group. In the estrogen replaced group, the expression of e-NOS was normalized.
CONCLUSIONS
Delayed estrogen replacement showed structural restoration of vaginal tissues. These results suggest that delayed estrogen replacement therapy could improve the sexual function in menopausal women.