The stage-dependent inhibitory effect of porcine follicular cells on the development of preantral follicles

Abstract

The objective of this study was to examine the effects of follicular cells on the in vitro development of porcine preantral follicles. In Experiment 1, one preantral follicle alone (Trt 1) was cocultured with a follicle of the same size with oocytes (Trt 2) or without oocytes (Trt 3). Preantral follicles cultured alone in vitro for 12 days had greater follicle diameters (1017±96 μm versus 706±69 or 793±72 μm, P<0.05), growth rates (201±0.3 versus 103±0.2 or 128±0.2, P<0.05) and oocyte survival rates (73% versus 48, or 25%, P<0.05) than other groups. The inhibitory effects of follicle cells on the growth of preantral follicles and oocyte survival rates were not enhanced by the addition of oocytectomized preantral follicles (Experiment 2). Follicles were cocultured with different sources of follicular cells in other experiments. Coculture with cumulus cells enhanced oocyte survival compared to the control (without coculture) and mural follicular cell groups (Experiment 3). The growth and survival rates of oocytes collected from the group of follicles cocultured with cumulus cells from large antral follicles (>3 mm) were greater ( P<0.05) than those from small antral follicles (<3 mm), or than the control group (without cumulus cells, experiment 4). No significant differences in the follicular diameters (674±30 μm versus 638±33 and 655±28 μm) and growth rate (105% versus 94 and 105%) were observed among the preantral follicles of the different treatments ( P>0.05). Taken together, coculture with the cells from large antral follicles (>3 mm) exerted a significant positive effect on oocyte survival. The growth and oocyte survival of preantral follicle cocultured with the same size of follicles (with or without oocyte) were inhibited. Growth and survival rates of preantral follicles and oocytes are improved by coculturing them with the cumulus cells derived from larger antral follicles.