<p>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 &beta;-catenin and Protein Kinase B (PKB)/AKT activity by exogenous SFRP-4 could be involved in steroidogenesis.<br /> 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 &beta;-catenin, pAKTser⁴⁷³, pGSK3&beta;ser⁹ were assessed by western blot or immuno-fluoresence.<br /> Results: In the presence of rhSFRP-4, there was 38% decreased E₂ levels compared to untreated FSH-primed cells (p&lt;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&lt;0.05). Unexpectedly, treatment with rhSFRP-4 prior to LH stimulation inhibited LH-induced P₄ secretion. Treatment with low (0.5 <em>ng/ml</em>) but not high (50 <em>ng/ml</em>) concentrations of rhSFRP-4 led to significantly increased levels of pGSK3&beta;ser⁹ (1.6-fold) and nuclear active &beta;-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&lt;0.05).<br /> Conclusion: Taken together, our results showed that rhSFRP-4 could directly induce terminal differentiation in GCs via the modulation of &beta;-catenin and PKB/AKT pathways and that it does so in a dose-dependent manner.</p>