Influence of aging on expression of FSHR mRNA in human ovary

Yoo, Sun Won; Lee, Yoon Jin; Cho, Hyun Hee; Kim, Mee Ran; Kwon, Dong Jin; Ryu, Ki Sung; Cha, Jung Ho; Lim, Yong Taik; Kim, Jang Heub; Kim, Jin Hong

Abstract

FSH is the central hormone for the regulation of ovarian function and acts by binding with specific receptor, FSHR, which is one of the G-protein coupled receptor family. The aging of ovary decreases the number and the activity of follicle, which results in the increase of FSH by reduction of inhibin and estrogen. The study on FSH level and FSHR mRNA expression in the ovary of perimenopausal women is the crucial step for the understanding of the menopausal mechanism.We studied FSHR mRNA expression of ovarian follicle by using in situ hybridization and QC RT-PCR. The fresh ovarian tissues and blood samples were obtained from premenopausal women in mid-follicular stage and postmenopausal women. The experimental samples were grouped as below 40 years old women, 40-44 years old ones, 45-49 years old ones, 50-54 years old ones, and postmenopausal women as negative control. To localize FSHR transcripts by in situ hybridization, we synthesized digoxigenin-labelled ssRNA probe (about 800 bp) and measured the degree of staining as 0, 1+, 2+ in the primary follicles which were independent to FSH effect. To do QC RT-PCR, we synthesized oligonucleotide primers (antisense: 5-GGCCCTGCTCCTGG- TCTCTTTG-3, sense: 3-AACAGCGGGAGTACCTTCGG-5) to form the 799 bp sized PCR products. We also synthesized 149 bp deleted DNA competitor by site-directed mutagenesis and then calculated the relative amount of target FSHR mRNA by comparing with competitor after PCR.There were significant reverse relationships between follicular number and aging (r=-0.934, P=0.01), and FSH level (r=-0.713, P<0.001). The similar amount of FSHR mRNA was expressed in the group of below 40 years by in situ hybridization. In the groups of above 40 years, the FSHR mRNA expression decreased progressively according to aging (r=-0.744, P<0.001) and FSH level (r=-0.771, P<0.001). But we could not find FSHR mRNA expression in menopausal ovaries. The amount of follicular FSHR mRNA was measured as 840.00+/-516.29 for the below 40 years group, 240.00+/-154.91 for the 40-44 years group, 40.00+/-21.90 for the 45-49 years group, 6.06+/-4.13 for the 50-54 years group, and 0.48+/-0.00 fg in the postmenopausal ovary. The amount of FSHR mRNA decreased with ovarian aging (r=-0.857, P<0.001) and FSH level (r=-0.771, P<0.001).These results demonstrate that the gradual increase of FSH and the decrease of FSHR mRNA expression in older than 40 years women are related to the changes of sex hormones. However the gradual decrease of the FSHR mRNA expression in the primary follicle may be due to the follicular aging itself. Therefore the menopausal transition already starts at the beginning of 40 years and one of the major cause of the menopause may be the reduction of FSHR mRNA expression followed the decrease of ovarian response to gonadotropins. The further studies should be required to elucidate the underlying mechanism and the associated factors of menopause.