Vitamin D receptor expression and potential role of vitamin D on cell proliferation and steroidogenesis in goat ovarian granulosa cells

This study aimed to investigate the expression of the vitamin D receptor (VDR) in goat follicles and to determine the effects of Vit D-3 supplementation on goat granulosa cells (GCs) function linked to follicular development. The results demonstrated that VDR was prominently localized in GCs, with expression increasing with follicle diameter. Addition of Vit D-3 (1 alpha,25-(OH)(2)VD3; 10 nM) to GCs caused an increase in VDR and in steroidogenic acute regulator (StAR) and 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) mRNA expression. Additionally, Vit D3 increased the cyclic adenosine monophosphate (CAMP), estradiol (E-2), and progesterone (P-4) levels, while it decreased anti-mullerian hormone receptor (AMHR) and follicle-stimulating hormone receptor (FSHR) mRNA expression (P < 0.05). Addition of FSH remarkably increased E-2, P-4, and CAMP levels (P < 0.05), and Vit D-3 further enhanced the E-2 and CAMP levels in the presence of FSH (P < 0.05). Vit D-3 significantly induced the mRNA expression of CDK4 and CyclinD1, and downregulated P21 gene expression (P < 0.05). In addition, Vit D-3 significantly decreased reactive oxygen species (ROS) production and increased the mRNA and protein expression of superoxide dismutase 2 (SOD2) and catalase (CAT) (P < 0.05). In conclusion, VDR is expressed in GCs of the goat ovaries and Vit D-3 might play an important role in GCs proliferation by regulating cellular oxidative stress and cell cycle related genes. Meanwhile, Vit D-3 enhances the E-2 and P-4 output of GCs by regulating the expression of 3 beta-HSD and StAR and the level of CAMP, which regulate steroidogenesis, supporting a potential role for Vit D-3 in follicular development. (C) 2017 Elsevier Inc. All rights reserved.