Background: The toxicity of silver nanoparticles (AgNPs) has been proven in the female reproductive system. Thymoquinone (TQ) is a natural antioxidant and bioactive component of Nigella sativa. Objective: We evaluated the efficacy of TQ on ovarian tissue following toxicity induced by AgNPs in female mice. Materials and Methods: 24 female NMRI mice (5–6 wk, an average weight of 33 gr) were randomly divided into 4 groups (n = 6/each): control, AgNPs (500 mg/kg, gavage), TQ (2.5 mg/kg, intraperitoneal injection), and TQ+AgNPs. Mice were treated every day for 35 days. Serum levels of malondialdehyde (MDA), total antioxidant capacity (TAC), luteinizing hormone, and follicle-stimulating hormone were measured. The optical disector and stereological techniques were utilized to estimate the follicular count, their volume at different developmental stages, and the structure of ovarian tissue. Results: In the AgNPs group, the serum concentrations of TAC (p = 0.01), luteinizing hormone (p < 0.001), follicle-stimulating hormone, the volume of corpus luteum (p < 0.001), and the number of follicles decreased significantly compared to the control group. Nevertheless, AgNPs significantly increased the MDA level. In the TQ+AgNPs group compared to the AgNPs group, a significant decrease in MDA level (p < 0.001) and a significant improvement in TAC (p = 0.03), and hormonal levels, the number of primary, preantral, and antral follicles (p = 0.04), and the volume of corpus luteum (p = 0.01) were observed. Conclusion: TQ improved the number of follicles by reducing oxidative stress and lipid peroxidation in AgNPs-damaged ovarian tissue.
