The RNF8/OPTN/KDM6A axis controls macrophage polarization to maintain testicular microenvironment homeostasis

Dysregulated immune responses may erroneously target normal reproductive tissues, thereby compromising the proper functioning of the reproductive system. Macrophages are the most abundant immune cells in the testes, however, the role of macrophages in spermatogenic function is not yet clear. This study indicated that the increase of pro-inflammatory macrophages impaired the development of spermatogenic cells, and the deficiency of RNF8 led to a proinflammatory state in the testicular microenvironment and diminished sperm production in mice. RNF8 mainly assembled K63-branched ubiquitin chains on autophagy receptor OPTN at K448 thus causing OPTN activation. The increased ubiquitination of OPTN promoted degradation of KDM6A via the autophagy-lysosome pathway, thereby inhibiting macrophage polarization towards the pro-inflammatory type and maintaining an immune privilege state in the testicular microenvironment. This homeostasis could be collapsed once the RNF8-OPTN-KDM6A axis was abnormal, subsequently resulting in remodeling of the testicular microenvironment. This study reveals the underlying mechanism of RNF8 on male reproduction, and the pro-inflammatory microenvironment resulting from RNF8 deficiency hindered spermatogenic cell differentiation, thereby impairing spermatogenic function.