Effect of ovarian aging on androgen biosynthesis in a cynomolgus macaque model

Abstract

Objective The role of androgens in chronic disease pathogenesis, cognitive function and libido during menopause is of increasing interest. The aim of this study was to characterize the distribution and expression of androgenic proteins in the macaque ovary and to investigate the relationship between serum androgen concentrations, follicle number, and the persistence of androgenesis in the aging macaque ovary.

Methods The subjects were 26 adult female cynomolgus macaques. Ovaries were immunostained for cytochrome P450 17α-hydroxylase/17–20 lyase (P450c17), 3β-hydroxysteroid dehydrogenase (3βHSD), and cytochrome b5 (cytb5). Based on primordial follicle counts, animals were divided into tertiles (low (≤200), intermediate (226–1232), and high (2372–4356)) to evaluate differences in androgen staining and changes in serum androgen concentrations following ovariectomy.

Results Positive immunostaining for P450c17 and cytb5 within the theca interna layer of growing follicles persisted in advanced atretic follicles and secondary interstitial cells (residual stromal cells). Ovaries with low follicle numbers had less staining for all androgenic proteins compared to ovaries with higher numbers of growing follicles. Immunostaining for cytb5 was the most reliable marker for persistent androgenesis in ovaries with minimal primordial follicle numbers (<100) and residual stromal cells. Following ovariectomy, a significant decrease in testosterone (−27.7%, −30.8%, −27.5%; p < 0.01) and androstenedione (−33.4%, −35.7%, −46.0%; p < 0.01) was observed in monkeys with low, intermediate, and high primordial follicle counts, respectively.

Conclusions Despite low follicle numbers, the aging macaque ovary retains the necessary proteins for androgenesis within residual stromal cells and contributes to peripheral androgen concentrations.

Key words::

• MENOPAUSE
• MONKEY
• ANIMAL MODEL
• OVARIAN RESERVE
• FOLLICLES
• AGING
• IMMUNOHISTOCHEMISTRY

Acknowledgements

The authors would like to thank the following: Melissa Ayers, Dewayne Cairnes, Patty Christian, Laurie Custer, Barbara Staton, Debbie Golden, Andrea Grantham, Margaret May, Hermina Borgerink, Jean Gardin, and Maryanne Post for their technical contributions; Alan J. Conley, BVSc, MS, PhD, Professor of Population Health and Reproduction, University of California-Davis, School of Veterinary Medicine and Michael R. Waterman, PhD, Professor of Biochemistry, Vanderbilt University School of Medicine for generously providing antiserum for cytochrome b5 and P450c17, respectively. For serum androgen measurements, the authors would like to thank the staff of the Endocrine Core Laboratory at Yerkes Primate Center. Finally, the authors would like to express their gratitude to Thomas B. Clarkson, DVM, Professor of Pathology (Comparative Medicine) for manuscript review and his continued support and guidance.

Conflict of interest The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.

Source of funding This work was supported by grants from the National Institutes of Health (NIH) National Center for Research Resources (NCRR) (K01 RR 021322-05 to CEW and T32 RR07009-32 to KE), National Heart, Lung, and Blood Institute (NHLBI) (R01 HL079421 to JRK) and the National Institute of Aging (NIA) (RO1 AG 027847 to SEA, R03-AG20290 to CRP). The contents are solely the responsibility of the authors and do not necessarily represent the view of the NCRR, NHLBI, NIA or NIH.