Growth of Mouse Oocytes in Ovaries Cultured In Vitro

Abstract

The early growth of mouse oocytes and the formation of zona pellucida in ovaries cultured in vitro were investigated histologically and compared to those in vivo. The ovaries excised from female mice at birth (Day 0) were cultured in vitro. The ovaries cultured for 0-6 days or obtained from 0-to 6-day old mice were treated by pronase and the diameters of naked oocytes were measured. Some ovaries were fixed, embedded, sectioned and stained by a periodic acid-Schiff method. On Day 0, almost all of the oocytes were without zona and less than 25μm in diameter. On Day 6, 3% of the oocytes reached more than 35μm in diameter. In vivo, as the oocytes developed, flat-shaped surrounding granulosa cells became cuboidal and their numbers increased. In the ovaries cultured in vitro, the early growth of oocytes associated with the formation of zone occurred without any noticeable changes in the morphology of granulosa cells.