Ovarian Stromal Cell-Conditioned Media, but Not Co-Culture, Improves Survival in Feline Follicles

Ovarian stromal cells play roles in in vivo folliculogenesis; however, little is known about their effect on in vitro cultured follicles. This study investigated the impact of ovarian stromal cell co-culture or conditioned medium (CM) on the survival and development of domestic cat follicles in vitro. Preantral (n = 148 follicles), early antral (n = 92), and antral (n = 22) stage cat follicles were divided into five groups (control, ovarian stromal cell co-culture, 20% CM, 50% CM, and 100% CM), cultured for 13 days, and evaluated for survival, growth, and the mRNA expression of CYP19A, GDF9, and FSHR. Additional follicles (n = 199) were isolated, divided into three groups (control, co-culture, and 100% CM), cultured for 10 days, and oocytes were subjected to in vitro maturation (IVM). More follicles (p ≤ 0.01) cultured in 100% CM survived until day 11 of culture than other groups. Antral follicle survival was significantly lower than pre- or early antral (p ≤ 0.0001). However, no differences (p > 0.05) in growth were detected across the treatments. CYP19A expression was upregulated (p ≤ 0.001) in the 50% CM-treated follicles. Furthermore, no differences (p > 0.05) were found in IVM rates between cultures. In summary, the findings demonstrate that conditioned medium collected from primary cultures of ovarian stromal cells improves in vitro survival of isolated cat follicles.