Sulforaphane Promotes Proliferation of Porcine Granulosa Cells via the H3K27ac-Mediated GDF8-ALK5-ERK Pathway

Follicle development, a crucial process in reproductive biology, hinges upon the dynamic proliferation of granulosa cells (GCs). Growth differentiation factor-8 (GDF8) is well-known as myostatin for inhibiting skeletal muscle growth, and it also exists in ovarian GCs and follicle fluid. However, the relationship between GCs proliferation and GDF8 remains elusive. Sulforaphane (SFN) is a potent bioactive compound, which in our study has been demonstrated to induce the expression of GDF8 in GCs. Meanwhile, we discover a novel role of SFN in promoting the proliferation of porcine GCs. Specifically, SFN enhances GCs proliferation by accelerating the progression of the cell cycle through the G1 phase to the S phase. By performing gene expression profiling, we showed that the promoting proliferative effects of SFN are highly correlated with the TGF-β signaling pathways and cell cycle. Among the ligand factors of TGF-β signaling, we identify GDF8 as a critical downstream effector of SFN, which acts through ALK5 to mediate SFN-induced proliferation and G1/S transition. In addition, we identify a noncanonical downstream pathway by which GDF8 induces the activation of MAPK/ERK to facilitate the cell cycle progression in GCs. Moreover, we reveal that the expression of GDF8 is regulated by SFN through epigenetic modifications of H3K27 acetylation. These findings not only provide mechanistic insights into the regulation of GCs proliferation but also establish a previously unrecognized role of GDF8 in follicle development, which have significant implications for developing strategies to improve female fertility.