Materials and Methods: All 25 mice were divided into five groups control, CTX group received CTX (150 mg/kg), quercetin + CTX group received IP injections of quercetin (75 mg/kg /daily) for 14 days, and CTX (150 mg/kg), CTX + bone marrow mesenchymal stem cells (BMMSCs) also received CTX and, 24 hours after the administration of CTX, approximately 1 × 106 BMMSCs were injected carefully into each testis of mice. Quercetin + CTX + BMMSCs group received quercetin and CTX (as in group quercetin + CTX), and BMMSCs were injected into each testis of the animals. Thirty-five days after the last injection of BMMSCs, blood samples were taken to gain serum and assess the testosterone level, and histopathological, biochemical, and sperm parameters analyses were performed.

Results: CTX led to testicular tissue damage and reduced the Johnson score and diameters of the seminiferous tube in the CTX group (P < 0.05). Also, the level of Antioxidant enzyme and testosterone was notably reduced in the CTX group (P < 0.05). The count and sperm quality were decreased significantly in the CTX group (P < 0.05). Administration of quercetin led to an increase in the level of testosterone and antioxidant enzymes and improved sperm parameters.

Conclusions: The present study shows the administration of quercetin can protect the testicle against CTX-related damage and improve oxidative stress damage and sperm parameters.