Exogenous Secreted Frizzledrelated Protein4 Modulates Steroidogenesis of Rat ‎Granulosa Cells Through Wnt/Bcatenin and Pi3k/Akt Signaling Pathways‎

Background: it has been reported that secreted frizzled-related protein-4 known as an antagonist of wnt signaling pathway plays a role in luteinization process of rodent granulosa cells. the purpose of this study was twofold: 1) to determine whether recombinant human secreted frizzled-related protein-4 (rhsfrp-4) could directly induce terminal differentiation of rat granulosa cells (gcs) and 2) to understand how the modulation of β-catenin and protein kinase b (pkb)/akt activity by exogenous sfrp-4 could be involved in steroidogenesis. methods: gcs were firstly stimulated with follicle-stimulating hormone (fsh) named as fsh-primed cells then were treated with luteinizing hormone (lh). then estradiol (e2) and progesterone (p4) production levels were assessed in the absence or presence of rhsfrp-4 treatment. the expression levels of activated -catenin, paktser473, pgsk3ser9 were assessed by western blot or immuno-fluoresence. results: in the presence of rhsfrp-4, there was 38% decreased e2 levels compared to untreated fsh-primed cells (p<0.05), and p4 production subsequently decreased. however, in gcs pre-treated with rhsfrp-4 prior to addition of fsh, p4 levels increased 2-fold compared with untreated cells (p<0.05). unexpectedly, treatment with rhsfrp-4 prior to lh stimulation inhibited lh-induced p4 secretion. treatment with low (0.5 ng/ml) but not high (50 ng/ml) concentrations of rhsfrp-4 led to significantly increased levels of pgsk3βser9 (1.6-fold) and nuclear active β-catenin (2.8-fold) in gcs compared with untreated cells. interestingly, pre-treating gcs with rhsfpr4 prior to lh stimulation resulted in a 38% decrease in paktser473 levels compared with those in lh-treated cells (p<0.05). conclusion: taken together, our results showed that rhsfrp-4 could directly induce terminal differentiation in gcs via the modulation of β-catenin and pkb/akt pathways and that it does so in a dose-dependent manner.