The calcium-dependent cell adhesion molecules, cadherins, regulate intercellular junction formation, cell sorting, and the establishment of cell polarity. Their important role in tissue remodeling suggests an involvement in ovarian cellular rearrangements throughout postnatal development. The ovary has a complex topology, and the ovarian follicle undergoes significant cellular rearrangements during its development. Cadherins have been detected previously in whole ovaries and in ovarian cells and cell lines with some immunolocalization in fetal and adult ovaries. This study examines the expression and localization of N- and E-cadherin throughout prepubertal ovarian and follicular development in the rat. We analyzed ovarian cadherin expression in rats from Day 19-20 of gestation to 25 days postpartum, during which follicle formation and folliculogenesis are the dominant ovarian events. Reverse transcriptase polymerase chain reaction detected N- and E-cadherin mRNA expression in the ovaries at all the ages examined. Semiquantification of Western blots of whole ovary extracts confirmed the presence of ovarian N- and E-cadherin protein at all ages with both showing peak expression at 7 days of age. Immunostaining revealed N- and E-cadherin expression in follicular and extrafollicular cell types, but only E-cadherin showed follicle-stage-dependent expression. The changes in cadherin expression, concurrent with ovarian growth and folliculogenesis, suggest a function for cadherins in the morphological and functional development of the prepubertal rat ovary.

Classical and atypical cadherins mediate calcium-dependent cell adhesion and play an important role in morphogenetic processes. We have shown, previously, N- and E-cadherin expression in the rat ovary. This expression, however, was not associated with specific follicle-restructuring events such as antrum formation and segregation of mural from cumulus granulosa cells suggesting that other cadherins may serve this function. In this study, RT-PCR and immunostaining techniques showed that three other cadherins are expressed throughout prepubertal ovarian development in the rat: one classical (P-) cadherin, and two atypical (K- and OB-) cadherins. RT-PCR analysis of isolated ovarian tissue compartments (granulosa cells and the residual ovarian tissue) agreed with the immunostaining results. Immunostaining showed P- and K-cadherin expression by granulosa, as well as thecal/interstitial cells, and also in oocytes of primordial follicles. P-cadherin expression was absent in oocytes of follicles in later stages of development compared to K-cadherin, which was found in oocytes at all stages of folliculogenesis. P-, K-, and OB-cadherin were expressed by the ovarian surface epithelial cells of neonatal animals but only P- and OB-cadherin expression were maintained in these cells in 25 day-old animals. Cellular OB-cadherin staining was absent in follicles at all stages of development and its expression was restricted to the ovarian hilar region and portions of the stroma. In summary, cadherin expression and distribution profiles changed during ovarian growth and folliculogenesis suggesting a role for cadherins in organizational and morphogenetic processes within the developing rat ovary.