Expression of BMP Receptors in Porcine Granulosa Cells (GCs) and Their Regulation by Luteinizing Hormone (LH)

Abstract

Bone morphogenetic proteins (BMPs) play critical roles in follicle growth and development. BMPs initiate signaling by assembling BMP receptors and activating Smads, which in turn alter expression of target genes. The mechanism underlying the regulation of the expression of BMP receptors and Smads during follicle development in pigs is still unknown. By quantitative real-time PCR, the mRNA expression of BMP receptors and Smads in granulosa cells (GC) was investigated. Cells were obtained from small porcine follicles (SF; <3 mm diameter) and dominant follicles (DF; >6 mm diameter); ActR1A and BMPR2 mRNA levels in DF were significantly higher ( P<0.05) than that in SF, whereas BMPR1B, Smad4 and Smad7 expression tended to decrease ( P>0.05). The levels of BMPR1A, ActR2, Smad1, Smad5, and Smad8 mRNA did not differ between DFs and SFs. To investigate the effect of LH on BMP receptors in GC, cells obtained from porcine DFs were cultured in medium supplemented with different doses of luteinizing hormone (LH). High doses of LH (4 IU mL −1) significantly decreased the concentration of estradiol (E2) and progesterone (P4) in medium and the expression of Cyp19a1 (P450 aromatase, P450arom) and Cyp11a1 (cholesterol side-chain cleavage enzyme P450, P450scc), while significantly increased viable cell numbers and up-regulated expression of cyclin dependent kinase-4 (CDK4) and cyclin D2. However, LH had no effect on the expression of BMP receptor genes. Thus, the present study indicates that the expression of members of the BMP signaling pathway in porcine GC is regulated during follicle development and the expression of BMP receptors are not regulated by LH in porcine GCs.