Abstract: Objective To investigate the effect of quercetin in cryoprotectant on the activity of follicles after cryopreservation of ovarian tissues. Methods Cortical pieces of 36 sexually mature ewe ovaries were randomly assigned to fresh control(CON)group, vitrification(VIT)group, vitrification with low, medium and high concentration(1, 5, 10 μmol/L)of quercetin(VWQ1, VWQ2, VWQ3)groups. The cortical pieces were rewarmed and cultured after vitrification to measure the estrogen levels, count the number of follicles and observe the morphological changes. The proliferating cell nucleus antigen of ovarian tissues was analyzed with immunohistochemistry. Tissue apoptosis was detected with TUNEL, and antioxidant capacity of ovarian tissues was determined with immunohistochemistry and visible light colorimetry. Results The proportion of morphological normal follicles was the highest while the number of apoptotic cells was the lowest in CON group(84.1%, P<0.001; 13.92±3.88, P<0.001). Compared with the VIT group, the VWQ1 group had higher rate of morphological normal follicles(76.5% vs 71.7%, P=0.035), fewer number of apoptotic cells(50.96±24.28 vs 73.44±35.47, P=0.017), and higher expressions of manganese superoxide dismutase(SOD-2)and catalase(CAT)［0.54(0.53, 0.55)vs 0.32(0.29, 0.51), P<0.001; 5.60±1.49 vs 3.48±1.21, P=0.008］. The VWQ3 group had the lowest rate of morphological normal follicles(61.2%, P<0.001), but the largest number of apoptotic cells(127.12±42.46, P<0.001). Conclusion Low concentration of quercetin in cryoprotection can reduce the oxidative damage on ovarian tissues and thus preserve the follicular activity, but excessively high concentration of quercetin can be harmful.

Key words: Ovarian tissue, Cryoprotective agent, Antioxidation, Vitrification, Sheep