Cell-free MSC secretome therapy ameliorates diabetic testicular injury via antioxidant mechanisms.

Diabetes mellitus is a metabolic disorder characterized by persistent hyperglycaemia that may impair male reproductive function. Mesenchymal stem/stromal cell-derived conditioned medium (MSC-CM) has emerged as a promising cell-free therapeutic approach for diabetes-associated complications. This study investigated the effects of CM obtained from MSCs cultured under normoxic (N-CM) or deferoxamine (DFX)-induced hypoxia-mimetic conditions (DFX-CM) on diabetes-related testicular dysfunction in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in Sprague Dawley rats using a single intraperitoneal injection of STZ (55 mg/kg). Diabetic rats received intraperitoneal administration of N-CM or DFX-CM for 3 weeks. Serum reproductive hormones were analysed by ELISA. Histological and histomorphometric evaluations were performed using haematoxylin and eosin staining, while ultrastructural alterations were examined by transmission electron microscopy (TEM). Oxidative stress markers and antioxidant enzyme activities were also assessed in testicular tissue. Diabetes reduced serum follicle-stimulating hormone (FSH), gonadotropin-releasing hormone, and luteinizing hormone levels, although only FSH showed a significant decrease. Histological analyses revealed mild impairment of spermatogenesis in diabetic rats without significant morphometric alterations. TEM demonstrated marked ultrastructural abnormalities in diabetic testes, including Sertoli cell degeneration and disrupted spermatogenic cell morphology. Both CM treatments attenuated these alterations, with improved ultrastructural organization observed particularly in Sertoli cells. Diabetes also induced oxidative stress, evidenced by reduced catalase and superoxide dismutase activities and elevated malondialdehyde and H2O2 levels. N-CM treatment showed the strongest antioxidant effects. These findings suggest that MSC-CM, particularly N-CM, may alleviate diabetes-induced testicular damage by restoring oxidative balance and preserving seminiferous tubule ultrastructure.