Comparison of Reproductive Function in Female TgMISIIR-TAg Transgenic and Wildtype C57BL/6 Mice

Transgenic TgMISIIR-TAg (TAg) mice express the oncogenic virus SV40 in Mullerian epithelial cells. Female TAg mice spontaneously develop epithelial ovarian carcinoma, the most common type of ovarian cancer in women. Female TAg mice are infertile, but the reason has not been determined. We therefore investigated whether female TAg mice undergo puberty, demonstrate follicular development, maintain regular cycles, and ovulate. Ovarian cancers in women commonly develop after menopause. The occupational chemical 4-vinylcyclohexene diepoxide (VCD) accelerates follicle degeneration in the ovaries of rats and mice, causing early ovarian failure. We therefore used VCD dosing of mice to develop an animal model for menopause. The purpose of this study was to characterize reproductive parameters in female TAg mice and to investigate whether the onset of ovarian failure due VCD dosing differed between female TAg and WT C57BL/6 mice. As in WT female mice, TAg female mice underwent puberty (vaginal opening) and developed cyclicity in patterns that were similar between the groups. Vehicle-only TAg mice had fewer ovulations (numbers of corpora lutea) than WT animals. VCD exposure delayed the onset of puberty (day of first estrus) in TAg as compared with WT mice. Morphologic evaluation of ovaries revealed many more degenerating follicles in TAg mice than WT mice, and more VCD-dosed TAg mice were in ovarian failure than VCD-dosed WT mice. These results suggest that despite showing similar onset of sexual maturation, TAg mice have increased follicular degeneration and fewer ovulations than WT. These features may contribute to the inability of female TAg mice to reproduce.

Assessing the pulsatility of luteinizing hormone in female vervet monkeys (Chlorocebus aethiops sabaeus)

Specific alterations in the pulsatility of luteinizing hormone (LH) are linked to obesity-related subfertility in ovulatory women. Vervet monkeys (Chlorocebus aethiops sabaeus) are an Old World nonhuman primate that develops obesity and has a menstrual cycle similar to humans. We evaluated follicular-phase LH pulses in 12 adult normal-weight female vervets. Serum was collected every 10 min for 4 h by using a tether device in conscious, freely moving monkeys on menstrual cycle days 2 through 5. Serum estradiol was collected daily during the follicular phase to identify the luteal-follicular transition. For comparison, we used data from 12 ovulatory normal-weight women who had undergone frequent blood sampling of early-follicular LH. LH pulse frequency was similar, with 2.8 ± 0.7 LH pulses during 4 h in vervets compared with 2.3 ± 0.7 LH pulses during 4 h in women. The LH pulse mass (percentage change in the pulse peak over the preceding nadir) was 123.2% ± 27.4% in vervets and 60.9% ± 14.9% in humans. The first day of low serum estradiol after the follicular-phase peak was denoted as the day of the luteal-follicular transition. Luteectomy was performed on luteal days 7 through 9, and corpora lutea were confirmed by histology. We demonstrate that follicular LH patterns in vervets are similar to those in humans and that the luteal phase is easily identified by monitoring daily serum estradiol. These findings demonstrate that vervet monkeys are a suitable animal model for evaluating LH pulse dynamics longitudinally in studies of diet-induced obesity.