Circular RNA circCSNK1G3 induces Leydig cells proliferation and promotes testosterone production through the miR-29b/IGF1 axis

Research has demonstrated the essential functions of circular RNAs (circRNAs) in testosterone production and spermatogenesis across various ruminant species. Nevertheless, the expression dynamics and biological activities of circRNAs in Leydig cells (LCs) are still not well understood. Herein, we identified a circular RNA that mediates LCs proliferation and testosterone synthesis, circCSNK1G3, and elucidated its underlying mechanisms. Multiple functional assays were performed to determine the biological functions of circCSNK1G3 and miR-29b in vitro. Furthermore, the relationship between circCSNK1G3 and miR-29b was confirmed using RNA pull-down analysis, fluorescence in situ hybridization (FISH), and dual-luciferase reporter experiments. Functionally, circCSNK1G3 increased testosterone levels by promoting LCs proliferation and stimulating testosterone production. Mechanistically, circCSNK1G3 operates mechanistically as an endogenous sponge for miR-29b in the cytoplasm of LCs, leading to enhanced expression of IGF1. By acting as a competitive endogenous RNA, circCSNK1G3 stimulates the biosynthesis of testosterone and the growth of LCs via the miR-29b/IGF1 axis, which may provide a potential basis for using circRNAs as target drugs to treat orchitis and azoospermia.