Effect of duration of dosing on onset of ovarian failure in a chemical-induced mouse model of perimenopause

In Brief Objective: Repeated daily dosing with 4-vinylcyclohexene diepoxide (VCD) causes gradual ovarian failure in mice. As a result, the animal undergoes ovarian failure, but retains residual ovarian tissue. The purpose of this study was to use a mouse model to regulate the induction of a period analogous to perimenopause in women. Design: Female B6C3F1 mice (28 days old; n = 8) were dosed daily for 10 or 20 days with VCD (160 mg/kg/d) or sesame oil. The animals were evaluated for reproductive function on days 10, 20, 35 after the onset of dosing, and on the day of follicle depletion. Each animal was killed at the specified time points, and ovaries, uteri, and plasma were collected. Results: VCD reduced (P < 0.05) the number of primordial (by 93.2%) and primary (by 85.1%) follicles after 10 days of dosing, whereas essentially all primordial and primary follicles were lost (P < 0.05) after 20 days of dosing. The average time to ovarian failure was on day 135 for 10-day-dosed mice and on day 52 for 20-day-dosed mice. Follicle-depleted mice in both groups had decreased (P < 0.05) ovarian and uterine weights. Circulating follicle-stimulating hormone levels were increased (P < 0.05) on day 44 after the onset of dosing in 10-day-dosed mice and on day 35 in 20-day-dosed mice. Conclusion: These results demonstrate that ovarian failure can be caused by VCD more rapidly if repeated daily dosing occurs for a longer period. Thus, the length of time leading up to ovarian failure (model for perimenopause) can be adjusted by varying the length of exposure. This study describes varying periods of impending ovarian failure in a chemical-induced murine model for perimenopause and postmenopause. By exposing animals for different durations to 4-vinylcyclohexene diepoxide, time from onset of dosing to ovarian failure ranged from an average of 52 to 132 days. The period before ovarian failure is proposed to be analogous to the perimenopausal period in women.