Effect of ovarian tissue storage in Morus nigra extract on the morphology and DNA fragmentation of ovine preantral follicles

This study demonstrated the effect of Morus nigra leaf extract during ovine ovarian tissue transportation on the survival and apoptosis of preantral follicles in vitro. High Performance Liquid Chromatography (HPLC) was used to determine the fingerprint chromatogram of the crude ethanolic extract. Four pairs of ovaries from four sheep were collected. The ovarian cortex was fragmented and one fragment was fixed in 10% buffered formaldehyde and processed for histological and TUNEL analysis (fresh control). The other fragments were placed in Minimal Essential Medium (MEM – control medium) or M. nigra extract (0.025; 0.05 or 0.1 mg/mL) and stored (simulating transport) at 4ºC for 6, 12 or 24 h. Preserved fragments (6 h) were also destined to histological and TUNEL analysis. HPLC analysis confirmed the presence of antioxidant compounds (rutin, isoquercetin e kaempferitrin) in the extract. There was a decrease (P < 0.05) in the percentage of morphologically normal preantral follicles after preservation in all treatments compared to the fresh control. The percentage of normal preantral follicles after preservation in M. nigra at 0.05 mg/mL for 6 h was higher (P < 0.05) than in MEM or 0.025 mg/mL M. nigra and similar (P > 0.05) to 0.1 mg/mL of the extract. Apoptosis increased (P < 0.05) after conservation for 6 h in all treatments compared to the fresh control. Moreover, TUNEL positive cells decreased (P < 0.05) after preservation in 0.05 or 0.1 mg/mL M. nigra compared to MEM or 0.025 mg/mL M. nigra. In conclusion, 0.05 mg/mL M. nigra extract can be used as a preservation medium for ovine ovarian tissue at 4°C for up to 6 h.