No abstract

Many circular RNAs (circRNAs) involved in the osteogenesis of human bone marrow mesenchymal stem cells (hBMSCs) have recently been discovered. The role of circHIPK3 in osteogenesis has yet to be determined. Cell transfection was conducted using small‐interfering RNAs (siRNAs). Expression of osteogenic markers were detected by quantitative reverse transcription‐polymerase chain reaction, western blotting analysis, and immunofluorescence staining. Ectopic bone formation models in nude mice were used to examined the bone formation ability in vivo. The autophagy flux was examined via western blotting analysis, immunofluorescence staining and transmission electron microscopy analysis. RNA immunoprecipitation (RIP) analysis was carried out to analyze the binding between human antigen R (HUR) and circHIPK3 or autophagy‐related 16‐like 1 (ATG16L1). Actinomycin D was used to determine the mRNA stability. Our results demonstrated that silencing circHIPK3 promoted the osteogenesis of hBMSCs while silencing the linear mHIPK3 did not affect osteogenic differentiation, both in vivo and in vitro. Moreover, we found that knockdown of circHIPK3 activated autophagy flux. Activation of autophagy enhanced the osteogenesis of hBMSCs and inhibition of autophagy reduced the osteogenesis through using autophagy regulators chloroquine and rapamycin. We also discovered that circHIPK3 and ATG16L1 both bound to HUR. Knockdown of circHIPK3 released the binding sites of HUR to ATG16L1, which stabilized the mRNA expression of ATG16L1, resulting in the upregulation of ATG16L1 and autophagy activation. CircHIPK3 functions as an osteogenesis and autophagy regulator and has the potential for clinical application in the future.

Osteoporosis is a frequently occurring bone remodeling disorder worldwide with one characteristic being decreasing bone mineral density and a predisposition to bone fracture, which diminishes patients' quality of life.Several studies showed that imbalance between the osteogenesis and adipogenesis of bone marrow mesenchymal stem cells (BMSCs) took part in the development of osteoporosis. In previous study, we found MIR22HG regulated the osteogenesis of human BMSCs positively. In this study, we found that MIR22HG was decreased during the adipogenesis of human BMSCs and exerted negative effects on adipogenesis with the involvement of Wnt/β-catenin signaling pathway both in vitro and in vivo. Nitazoxanide could inhibit Wnt signaling and relieve MIR22HG's suppression on adipogenesis. These findings indicated that MIR22HG had great potential in clinical application for osteoporosis treatment and prevention.