MiR-29c-3p reduces bone loss in rats with diabetic osteoporosis via targeted regulation of Dvl2 expression

The aim of this study was to investigate the influence of micro ribonucleic acid (miR)-29c-3p on rats with diabetic osteoporosis (DOP) and its underlying mechanism.

A total of 30 specific pathogen-free (SPF)-grade male Wistar rats aged 6-week-old were randomly selected and divided into three groups according to different intervention means, including: NC group (control rats only injected with normal saline), DOP group (rats with DOP induced by injection of streptozotocin), and ME group (DOP rats injected with miR-29c-3p agonist for 4 consecutive weeks). The changes in blood glucose and body weight were recorded in the rats of each group every week. Enzyme-linked immunosorbent assay (ELISA) was applied to detect the content of bone turnover markers (BTMs) in serum, such as alkaline phosphatase (ALP), osteocalcin (OC), and procollagen type I N-terminal propeptide (PINP). The variations in serum calcium (Ca) and phosphorus (P) levels in the abdominal aorta were determined using an atomic absorption spectrometer in the three groups. Meanwhile, bone mineral density (BMD) of femur and lumbar vertebra (L1-L4) were examined. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to measure the changes in messenger RNA (mRNA) expressions of miR-29c-3p and Disheveled 2 (Dvl2) in the bone tissues of intervened rats. In addition, the staining and expression changes of Dvl2 protein in bone tissues were determined via immunohistochemistry.

The rats in NC group had normal behavioral activities, normally increased body weight, sensitive responses, as well as normal and stable blood glucose. In DOP group, the rats manifested clinical symptoms of diabetes mellitus (DM) (i.e., polydipsia, polyphagia, polyuria, and weight loss), lackluster hairs, decreased behavioral activities, slow responses, and blood glucose at a concentration higher than 16.7 mmol/L. However, the blood glucose rose first, and then, declined and it was maintained at a level higher than normal concentration in ME group. Meanwhile, the rate of weight loss significantly decreased. The results of qRT-PCR indicated that the relative expression level of miR-29c-3p in bone tissues of DOP group was remarkably lower than that in NC group (p<0.01). However, it was significantly higher in ME group than that in DOP group (p<0.05). DOP group exhibited significantly upregulated serum BTMs (ALP, CTX-1, OC, TRACP-5b, and PIPN) when compared with NC group (p<0.05) and ME group (p<0.05). Furthermore, femoral BMD decreased in DOP group (p<0.05) while increased in ME group, showing statistically significant difference between the two groups (p<0.05). Immunohistochemistry results indicated that the bone tissues of DOP rats were deeply stained, and protein expression of Dvl2 protein was significantly higher in comparison with NC group. The bone tissues were lightly stained in ME group, and the protein expression of Dvl2 was lower than that in DOP group. Besides, qRT-PCR results demonstrated that the mRNA expression changes of Dvl2 were consistent with its protein expression trends.

MiR-29c-3p reduces bone loss in rats with DOP via targeted regulation of Dvl2 expression.