Effects of Inhibin A on Apoptosis and Proliferation of Bovine Granulosa Cells

SIMPLE SUMMARY: The ovarian granulosa cells play a crucial role in oocyte nourishing, secreting hormones that create functional bidirectional crosstalk with the oocyte. During follicle development, granulosa cells replicate, secrete hormones, and provide a critical microenvironment for follicular growth. Proliferation and differentiation of granulosa cells are essential for normal follicular growth, development of the oocyte, ovulation, and luteinization. Inhibins negatively regulate the production and secretion of follicle-stimulating hormone from the anterior pituitary, controlling ovarian follicle development. This study was aimed to explore the cellular and molecular adaptation of bovine granulosa cells under different concentrations of inhibin A. For instance, several physiological traits (cell viability, apoptosis, mitochondrial membrane potential, and cell proliferation) were assessed under different concentrations (0, 20, 50, and 100 ng/mL) of inhibin A. Results depicted that high doses of inhibin A boosted cell viability, mitochondrial membrane integrity, and cell proliferation, while inhibiting apoptotic rate in bovine granulosa cells. ABSTRACT: Inhibin A is well known for its inhibitory properties against follicle-stimulating hormone (FSH), released through a pituitary–gonadal negative feedback loop to regulate follicular development. Ovarian folliculogenesis, hormonal biosynthesis, and gametogenesis are dependent on inhibins, playing vital roles in promoting or inhibiting cell proliferation. The present study explored the physiological and molecular response of bovine granulosa cells (GCs) to different concentrations of inhibin A in vitro. We treated the primary GCs isolated from ovarian follicles (3–6 mm) with different levels of inhibin A (20, 50, and 100 ng/mL) along with the control (0 ng/mL) for 24 h. To evaluate the impact of inhibin A on GCs, several in vitro cellular parameters, including cell apoptosis, viability, cell cycle, and mitochondrial membrane potential (MMP) were detected. Besides, the transcriptional regulation of pro-apoptotic (BAX, Caspase-3) and cell proliferation (PCNA, CyclinB1) genes were also quantified. The results indicated a significant (p < 0.05) increase in the cell viability in a dose-dependent manner of inhibin A. Likewise, MMP was significantly (p < 0.05) enhanced when GCs were treated with high doses (50, 100 ng/mL) of inhibin A. Furthermore, inhibin A dose (100 ng/mL) markedly improved the progression of the G1 phase of the cell cycle and increased the cell number in the S phase, which was supported by the up-regulation of the proliferating cell nuclear antigen PCNA (20, 50, and 100ng/mL) and CyclinB (100 ng/mL) genes. In addition, higher doses of inhibin A (50 and 100 ng/mL) significantly (p < 0.05) decreased the apoptotic rate in GCs, which was manifested by down regulating BAX and Caspase-3 genes. Conclusively, our study presented a worthy strategy for the first time to characterize the cellular adaptation of bovine GCs under different concentrations of inhibin A. Our results conclude that inhibin A is a broad regulatory marker in GCs by regulating apoptosis and cellular progression.