Transplanted human p75-positive stem Leydig cells replace disrupted Leydig cells for testosterone production.

Previous studies have demonstrated that rodent stem Leydig cell (SLC) transplantation can partially restore testosterone production in Leydig cell (LC)-disrupted or senescent animal models, which provides a promising approach for the treatment of hypogonadism. Here, we isolated human SLCs prospectively and explored the potential therapeutic benefits of human SLC transplantation for hypogonadism treatment. In adult human testes, p75 neurotrophin receptor positive (p75) cells expressed the known SLC marker nestin, but not the LC lineage marker hydroxysteroid dehydrogenase-3β (HSD3β). The p75 cells which were sorted by flow cytometry from human adult testes could expand in vitro and exhibited clonogenic self-renewal capacity. The p75 cells had multi-lineage differentiation potential into multiple mesodermal cell lineages and testosterone-producing LCs in vitro. After transplantation into the testes of ethane dimethane sulfonate (EDS)-treated LC-disrupted rat models, the p75 cells differentiated into LCs in vivo and secreted testosterone in a physiological pattern. Moreover, p75 cell transplantation accelerated the recovery of serum testosterone levels, spermatogenesis and reproductive organ weights. Taken together, we reported a method for the identification and isolation of human SLCs on the basis of p75 expression, and demonstrated that transplanted human p75 SLCs could replace disrupted LCs for testosterone production. These findings provide the groundwork for further clinical application of human SLCs for hypogonadism.