Ovariectomy increases squamous metaplasia of the uterine horns and survival of SENCAR mice fed a vitamin A-deficient diet

Background: Retinoic acid is necessary for the growth and differentiation o f organisms and exerts its molecular actions by binding to specific nuclear receptors that belong to the thyroid-steroid hormone receptor superfamily. Steroids and retinoids control the differentiation of the female reproduct ive epithelia: estrogen maintains the squamous differentiation of vaginal a nd ectocervical epithelia, whereas retinoic acid maintains the simple colum nar endocervical and uterine epithelia. These lining epithelia transform in to a squamous metaplastic phenotype in vitamin A-deficient animals. Further more, mortality due to vitamin A deficiency is usually attributed to infect ion resulting in part from dysfunction of the protective epithelia. Objective: Our objective was to test the hypothesis that estrogen depletion might change the squamous metaplastic response to vitamin A deficiency and affect animal survival. Design: We used female SENCAR mice maintained on a purified vitamin A-defic ient diet containing either 0 or 3 mu g retinoic acid/g diet. Mice were eit her ovariectomized or intact. Squamous cells arising in the normally simple columnar epithelium of the endocervix and uterine cavity were monitored by keratin 5 expression with immunohistochemistry. Results: Ovariectomy did not change the time to onset of vitamin A deficien cy. It increased the number of squamous metaplastic cells and prolonged sur vival in mice consuming a vitamin A-deficient diet by as much as 40%. Conclusions: Factors other than epithelial differentiation per se control s urvival outcome of vitamin A-deficient mice. The results also show a signif icant increase in longevity of vitamin A-deficient mice when ovariectomized .