Absence of colony-stimulating factor-1 in osteopetrotic (csfm(op)/csfm(op)) mice results in male fertility defects

Previous studies have shown that the mononuclear phagocyte growth factor, colony-stimulating factor-1 (CSF-1), has an important role in female reproduction. Mating experiments with osteopetrotic (csfm(op)/csfm(op)) mice, which possess an inactivating mutation in the CSF-1 gene, suggested that there are male, as well as female, reproductive defects. In the present study, we have shown that male csfm(op)/csfm(op) mice have a sevenfold lower concentration of circulating testosterone (T) and a significantly lower intratesticular T concentration than wild-type mice. These lowered T concentrations were associated with a reduction in mating capability and a reduction in the number of viable sperm. Reconstitution of male csfm(op)/csfm(op) mice with either circulating T in the adult or circulating CSF-1 throughout the postnatal period completely restored viable sperm numbers and significantly restored sexual behavior. These observations, coupled with the close association of Leydig cells with testicular macrophages and the proposed function of these macrophages in the regulation of Leydig cell steroidogenesis, suggest that CSF-1-regulated testicular macrophages play an important role in male reproduction.