Evidence for an association between Wnt-independent -catenin intracellular localization and ovarian apoptotic events in normal and PCO-induced rat ovary

Abstract

The association of secreted frizzled related protein type 4 (Sfrp4) as an antagonist of Wnt mole-cules in apoptotic events has been reported previously. Moreover, its increased expression has been reported in the ovary of women with polycystic ovary (PCO). We have demonstrated in-creased Sfrp4 in PCO-induced rat ovary related to an increased number of apoptotic follicles showing nuclear ?catenin subcellular localization. The aims of present study were twofold 1) to ascertain nuclear ?catenin presence with apoptosis by using immunolocalization of Bax and active cleaved casapase-3, and 2) to elucidate whether Sfrp4 could be an inducer of apoptosis by using isolated rat granulosa cell culture in the presence of recombinant human SFRP4. To this end, immuno-expression of two key molecules in Wnt signaling, GSK3? and ?-catenin and apoptotic markers were investigated in normal and PCO-induced rat ovary by daily administration of testos-terone propionate (TP) for four weeks. We showed that in PCO-induced as well as in normal ova-ries there was nuclear or cytoplasmic subcellular localization of GSK3? and a weak pGSK3?ser9 immuno-staining in apoptotic granulosa cells. Interestingly, intracellular ?catenin localization was observed in Bax and active caspase-3 positive granulosa cells in normal as well as in PCO-induced rat ovary. Treatment of granulosa cells with rhSFRP4 showed co-localization of nuclear subcellu-lar ?-catenin and active caspase-3 as revealed by double immuno-fluorescence. Our results suggest that rhSFRP4 induces apoptosis and that there is an association between Wnt-independent ?-catenin nuclear subcellular localization and apoptotic events of rat ovary.