Role of ascorbic acid in promoting follicle integrity and survival in intact mouse ovarian follicles in vitro

Ascorbic acid has three known functions: it is necessary for collagen synth esis, promotes steroidogenesis and acts as an antioxidant. Within the ovary , most studies have concentrated on the role of ascorbic acid in luteal for mation and regression and little is known about the function of this vitami n in follicular growth and development. Follicular growth and development w ere investigated in this study using an individual follicle culture system that allows the growth of follicles from the late preantral stage to Graafi an morphology. Follicles were isolated from prepubertal mice and cultured f or 6 days. Control media contained serum and human recombinant FSH. Further groups of follicles were cultured in the same media but with the addition of ascorbic acid at concentrations of either 28 or 280 mu mol l(-1). Additi on of ascorbic acid at the higher concentration significantly increased the percent-age of follicles that maintained basement membrane integrity throu ghout culture (P < 0.001). Ascorbic acid had no effect on the growth of the follicles or on estradiol production. Metalloproteinase 2 activity tended to increase at the higher concentration of ascorbic acid and there was a si gnificant concomitant increase in the activity of tissue inhibitor of metal loproteinase 1 (P < 0.01). Follicles cultured without the addition of serum but with FSH and selenium in the culture media underwent apoptosis. Additi on of ascorbic acid to follicles cultured under serum-free conditions signi ficantly reduced apoptosis (P < 0.05). From these data it is concluded that ascorbic acid is necessary for remodelling the basement membrane during fo llicular growth and that the ability of follicles to uptake ascorbic acid c onfers an advantage in terms of granulosa cell survival.