Effects of icariin on ovarian function in d-galactose-induced aging mice

Abstract

In this study, effects of icariin (Ica) on were examined in a mouse model of d-galactose (D-gal)-induced ovarian aging. Kunming white mice were divided into three groups: aging group induced with D-gal, experiment group treated with Ica at low (50 mg/kg), middle (100 mg/kg) and high (200 mg/kg) concentrations, and control group with no treatment. Ovarian histomorphology, serum FSH, LH and E₂ levels, and reproductive function were compared among the groups. Ovarian expression of Amh, Bax and Bcl-2 was examined by qPCR and western blotting. Our results showed that diameters of secondary and tertiary follicles were significantly reduced in the aging group when compared with control group (P < 0.01), and were restored to normal in Ica 100 and Ica 200 treatment groups. The diameter of atretic follicles was significantly smaller in the aging group compared with control group and Ica 200 treatment group (P < 0.05). The proportion of secondary and atretic follicles was higher in the aging group compared with control group, Ica 100 and 200 treatment groups, whereas the proportion of tertiary and mature follicles was reduced in the aging group versus control, Ica 100 and 200 groups. The aging group lacked mature follicles, whereas Ica treatment induced mature follicle development. Primary and secondary follicles exhibited similar theca cell numbers and theca interna and externa cell layers in all groups examined, whereas theca interna and externa cell layers were decreased and increased, respectively, in tertiary follicles of aging group compared with control and I 200 groups. In the aging group, FSH and LH levels were significantly higher than those in control and Ica 200 groups (P < 0.05), and the E₂ level was significantly reduced compared with control (P < 0.01), Ica 200 (P < 0.01), and Ica 100 (P < 0.05) groups. Serum hormone levels were equivalent in the control, Ica 100 and Ica 200 groups. The pregnancy rate was reduced in the aging group compared with other groups. The average litter size per birth, birth litter weight, and weaning weight of litters were all significantly lower in the aging group compared with control, Ica 100 and 200 groups (P < 0.05). The ovarian expression of AMH and Bcl-2 mRNA was significantly reduced in the aging group compared with those in control and Ica-treated groups (P < 0.01). In contrast, Bax expression was significantly higher in the aging group compared with all other groups (P < 0.01), and the Bcl-2/Bax ratio was markedly reduced in aging group compared with control, Ica 100 and 200 groups (P < 0.01), and Ica 50 group (P < 0.05). Ovarian expression of AMH protein was elevated in the Ica 100 group compared with the aging, control and Ica 50 groups (P < 0.01) and Ica 200 group (P < 0.05). Ovarian Bcl-2 protein levels and the Bcl-2/Bax ratio were significantly higher in the Ica 100 group than those in the Ica 50, 200 and aging groups (P < 0.05), and were similar or reduced (P < 0.05), respectively, compared to those in control group. Ovarian Bax expression was similar in each group. These findings suggest that Ica can improve ovarian follicular development, inhibit follicular atresia, decrease FSH and LH levels and increase E₂, upregulate ovarian AMH expression and increase the Bcl-2/Bax ratio in aging mice. Therefore, Ica can partially restore ovarian function of aging mice and enhance their fertility. Optimal reproductive effects were obtained with the Ica 100 group.

Keywords: Icariin; Mice; Ovarian function; d-galactose.