Ovary

Bovine Model for the Study of Reproductive Aging in Women: Follicular, Luteal, and Endocrine Characteristics

Abstract
At present, there is no well characterized animal model to study the effects of aging on fertility in women. The objectives of the study were to characterize age related changes in ovarian and endocrine functions in old cows and to investigate the validity of a bovine model for the study of human reproductive aging. We tested the hypotheses that aging in cattle is associated with 1) elevated concentrations of gonadotropins and reduced concentrations of steroid hormones in systemic circulation, and 2) increased recruitment of ovarian follicles during wave emergence. Daily ultrasonography was performed in 13-14 year old cows (n = 10) and their 1-4 year old daughters (n = 9) for one interovulatory interval to study ovarian function. Plasma samples were obtained every 12 hr for determination of FSH, LH, progesterone, and estradiol concentrations. Circulating FSH concentrations were higher (P = 0.009) during follicular waves in old cows than in their daughters, but the number of 4-5 mm follicles recruited into a wave was lower (P = 0.04) in old cows. Plasma LH concentrations did not differ between groups (P = 0.4), but the ovulatory follicle in 2-wave cycles was smaller in old cows (P = 0.04). Plasma estradiol concentrations were higher (P = 0.01) in old cows, and luteal phase progesterone tended to be lower (P = 0.1). We conclude that these changes are consistent with those reported for women approaching menopause transition. Therefore, our results validate the use of bovine model to study reproductive aging in women.

Key words: Ovary • Aging • Follicle-stimulating hormone • Follicular development • Steroid hormones

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