GDF5 promotes proliferation and inhibits apoptosis of Hu sheep ovarian granulosa cells via the NGF pathway.

This study aimed to investigate the effects and underlying mechanisms of growth differentiation factor 5 (GDF5) in follicular development of Hu sheep. In the present study, GDF5 was prominently localized in ovarian granulosa cells (GCs), and its expression increased progressively with follicle development. In vitro studies demonstrated that GDF5 knockdown suppressed GC proliferation and promoted apoptosis by downregulating cell cycle-related genes (PCNA, CCND1 and CDK6) and upregulating apoptosis-related gene (BAX). Meanwhile, GDF5 overexpression inhibited GC apoptosis and promoted proliferation by upregulating cell cycle-related genes and downregulating the apoptosis-related genes. RNA-seq revealed that nerve growth factor (NGF) expression was significantly downregulated following GDF5 overexpression. Subsequently, we found that the expression of NGF was significantly higher in > 5 mm follicles than in smaller follicles. Functional experiments indicated that NGF knockdown enhanced GC proliferation and repressed apoptosis by upregulating PCNA and downregulating BAX, whereas NGF overexpression exerted opposite effects. Furthermore, rescue experiments confirmed that NGF knockdown reversed the effects of GDF5 knockdown, thereby restoring GC proliferation and suppressing apoptosis, while NGF overexpression attenuated the pro-proliferation and anti-apoptosis functions of GDF5 overexpression. Altogether, these results demonstrated that GDF5 regulated GC proliferation and apoptosis via the NGF pathway, providing novel insights into the regulatory network governing follicular development.