Follicle-stimulating hormone-receptor expression in the aging human ovary

Abstract

The follicles in a human ovary gradually decline in number during infancy, adolescence and the reproductive years. However, during the perimenopausal period there is a more rapid decline in follicles. Older women have fewer granulosa cells in their follicles than younger women. The older ovary is less responsive to gonadotropins, especially FSH. It is hypothesized that age-related, decreased responsiveness to FSH is due to decreased FSH-receptor (FSH-R) levels and/or alternate splicing of FSH-R mRNA resulting in defective (impaired) receptors. Human ovarian follicles of sizes ranging from 3 to 7 mm in diameter from 26-46 year-old women were isolated, snap frozen and stored at -80°C. RNA was isolated and real time PCR performed to measure the FSH-R mRNA levels in the follicles. Linear regression analysis was performed on FSH-R mRNA levels within follicle size categories as a function of age. The regression analysis was found to be non significant. Therefore, we reject the hypothesis, which stated that FSH-R mRNA levels within follicles decrease as the ovary ages. To analyze alternate splicing of FSH-R mRNA, two oligonucleotide primer sets were designed. RT-PCR of total RNA from follicles of 26-46 year-old women was performed. PCR products were sequenced to determine the degree of homology for the FSH-R with the human FSH-R variant 1 published in Gene bank. There was 99.7% sequence homology between the FSH-R PCR amplimers and human FSH-R variant 1. This suggests that impaired ovarian response is not due to alternate splicing of the FSH-R mRNA in older women, and is inconsistent with the hypothesis that alternate splicing of FSH-R mRNA is the cause for decreased response to FSH in an aging human ovary. Accordingly, decreased response may be due to other factors, perhaps FSH/FSH-R post receptor signaling mechanisms.