Ce Chen* Yingying Dong* Fei Liu Chengge Gao Cui Ji Yonghui Dang 4 Xiancang Ma 1 Yong Liu 1Department of Psychiatry, First Affiliated Hospital of Medical College Xi’an Jiaotong University, Xi’an 710061, Shaanxi, People’s Republic of China; 2Clinical Research Center of Shaanxi Province for Dental and Maxillofacial Diseases, College of Stomatology, Xi’an Jiaotong University, Xi’an 710004, Shaanxi, People’s Republic of China; 3The Hospital of Xidian University, Xi’an 710071, Shaanxi, People’s Republic of China; 4College of Medicine & Forensics, Xi’an Jiaotong University Health Science Center, Xi’an 710061, Shaanxi, People’s Republic of China; 5The Institute of Neurobiology, Xi’an Jiaotong University, Xi’an 710061, Shaanxi, People’s Republic of China

OBJECTIVE:Postmenopausal osteoporosis (POMP) is a serious disorder with significant physical, psychosocial, and financial consequences, which greatly reduce the postmenopausal women's life quality. The related issues of postmenopausal osteoporosis are increasingly concerned by society. Past researches have shown that miRNAs play an important role in the occurrence and development of postmenopausal osteoporosis. However, the role of miR-218 and miR-618 in the osteoporosis regulation is still unclear.MATERIALS AND METHODS:First of all, we investigated the alteration of miR-218 and miR-618 during osteoclastogenesis of RAW264.7 cells. Next, we transfected RAW264.7 cells with miR-218 or miR-618 mimics and inhibitors to explore the influences of miR-218 and miR-618 on osteoclast differentiation. Then, we conducted bioinformatics analysis and luciferase reporter assay to identify and test the target gene of miR-218 and miR-618.RESULTS:MiR-218 and miR-618 were down-regulated when RAW264.7 cells differentiated into osteoclasts. In addition, overexpression of miR-218 or miR-618 attenuated RAW264.7 cells differentiated into osteoclasts in vitro, whereas inhibition of miR-218 or miR-618 promoted this progress. This was demonstrated by increased expression of osteoclast-specific genes and TRAP staining. TLR-4 was confirmed to be the direct target of miR-218 and miR-618 by bioinformatics and luciferase reporter assay.CONCLUSIONS:These results suggested that miR-218 and miR-618 play an important role in osteoclastogenesis via TLR-4/MyD88/NF-κB signaling pathway. Thus, targeting miR-218 and miR-618 promise a therapeutic potential in the treatment of osteoporosis.

Ovarian aging has been associated with increased levels of reactive oxygen species and the deficiencies of antioxidant defense. The antioxidant peroxiredoxin 4 (Prdx4), as a member of Prdx protein family, controls cellular oxidative stress by reducing H2O2 levels. In previous studies, we provided evidence that Prdx4 was abundantly expressed in mouse and human ovaries and expression of Prdx4 in matured follicles was higher than that in immatured follicles. Accordingly, we speculated that Prdx4 expression could be associated with follicle development and it may be as a part of the antioxidative mechanism in follicular development. In this study, we demonstrated that Prdx4 was mainly expressed in the granulosa cells of mouse ovaries and the expression levels significantly increased along development of follicles. However, the expression levels of Prdx4 decreased when mice reached the aged stage (18 months old). Likewise a similar pattern that was observed in the mice study was also found in human ovaries where Prdx4 was expressed lower in premenopausal women than young women. Subsequent in vitro experiments indicated that Prdx4 mRNA and protein levels both increased with H2O2 in a concentrationdependent manner, but decreased rapidly with high concentration of H2O2, and the changes were closely related to cell proliferation. Taken together, these findings argue our understanding on the role of oxidative stress and antioxidant in follicular development and ovarian aging.