Effects of Alginate Concentration and Ovarian Cells on In Vitro Development of Mouse Preantral Follicles: A Factorial Study

In the present study, the effects of alginate (ALG) concentration and ovarian cells (OCs) on the development and function of follicles were simultaneously evaluated.

In the first step, preantral follicles (100-130 µm in diameter) were mechanically isolated from the ovaries of 2-week-old NMRI mice, encapsulated in the absence or presence of OCs in 0.5, 0.75 and 1% ALG hydrogels, and cultured for 14 days. The morphology, diameter, survival and antrum formation rates of follicles and the maturation of oocytes were evaluated during culture. In the second step, preantral follicles were cultured in the best ALG concentration (determined in the first step), in the absence or presence of OCs. Afterward, the amount of DNA fragmentation, connexin 37 and connexin 43 proteins expression and estradiol, progesterone and androstenedione secretions by the follicles and the quality of mature (MII) oocytes were assessed.

Our data revealed that in the absence of OCs, follicles of 0.5% group showed a higher survival rate than 0.75 and 1% groups (71.87 vs. 52.52 and 40%; P < 0.05); nonetheless, the antrum formation rate of 1% group was higher and its oocytes degeneration rate was lower than other groups. Furthermore, it was shown that co-culture of follicles with OCs relatively increased the follicles diameter, survival, antrum formation, and GV to GVBD/MII transition rates. At last, the comparison of 0.5%-OCs and 0.5%+OCs groups indicated that co-culture condition resulted in more progesterone production (1.8±0.2 vs. 3.2±0.4 ng/ml, respectively; P < 0.05) and also decreased oocyte’s cortical granules abnormalities (100 vs. 40% for 0.5%-OCs and 0.5%+OCs groups).

The present study revealed that 0.5% ALG hydrogel is relatively more suited to preantral follicles culture and in the presence of OCs mimics the ovarian condition better than 0.75 and 1% ALG hydrogels.