Changes in the mouse ovarian surface epithelium with age and ovulation number

The cell biology of ovarian surface epithelium (OSE) was studied in mice of varying age and lifetime total ovulation number (OV#), to determine the relative importance of these factors in control of OSE proliferation and development of invaginations and cysts. Ovaries from Swiss Webster mice (total OV# median: range [n mice]) were collected at 4 weeks of age (prepubertal; 0[9]), from 3-month virgins (113: 11-235 [55]), from 12-month old breeders (217: 97-386 [21]) and from 8-month virgin mice, housed in split cages alongside a male, to induce continuous oestrous cycles (629: 456-908 [16]). Scanning electron microscopy revealed cuboidal and squamous cells in OSE from all ages. Higher total OV# markedly increased the rate of OSE invagination and layering. Histology showed the incidence of cysts, which had the appearance of benign serous cystadenomata, increased with age rather than total OV#.