DNA damage and primordial follicle activation after in vitro culture of sheep ovarian cortex in Morus nigra leaf extract

This study evaluated the effect of Morus nigra leaf extract, with or without supplementation, on morphology, activation and DNA damage of preantral follicles cultured within sheep ovarian tissue. Ovaries were collected and divided into fragments, being one fixed for histological and Terminal deoxynucleotidyl transferase (TdT) mediated dUTP nick-end labeling (TUNEL) analysis (fresh control). The remaining fragments were cultured for 7 days in alpha minimum essential media (alpha-MEM) supplemented with bovine serum albumin (BSA), insulin, transferrin, selenium, glutamine, hypoxanthine and ascorbic acid (alpha-MEM+; control medium) or into medium composed of M. nigra extract without supplements (0.1; 0.2 or 0.4mg/mL) or supplemented with the same substances described above for alpha-MEM+ (MN 0.1(+); 0.2(+) or 0.4(+) mg/mL). Then, tissues were destined to histological and TUNEL analysis. The alpha-MEM+ treatment had more morphologically normal follicles than all M. nigra extract treatments. However, alpha-MEM+ treatment also showed signs of atresia because the percentage of TUNEL positive cells was similar in alpha-MEM+ and in 0.1mg/mL M. nigra without and with supplements. Moreover, a reduction in the primordial follicles and an increase in the growing ones were observed in all treatments, except 0.2mg/mL M. nigra. In conclusion, the follicles cultured at 0.1mg/mL M. nigra extract were in good condition and able to continue their development, as demonstrated by the same rates of DNA damage and follicular activation as the control medium.