Cyclic Peptide D7 Promotes Osteogenesis and Inhibits Osteoclastogenesis by Regulating Redox Balance of Bone Remodeling

Abstract

BackgroundMilitary training usually causes excessive physical burden to the bones and joints of soldiers, which in turn disturbs the balance of bone homeostasis and eventually induces bone metabolic diseases. In our previous studies, a cyclic peptide D7 in was characterized through phage display technology from the peptide phage display library (Ph.D.‑C7C) and was proven to enhance the adhesion, expansion, and proliferation of bone marrow mesenchymal stem cells (BMSCs) on the biomaterial scaffold. However, we found that cyclic peptide D7 also has a certain affinity for mouse calvarial osteoblast precursor cells (OPCs) and bone marrow-derived monocytes/macrophages (BMMs). To investigate whether D7 can protect physiological bone remodeling and maintain bone homeostasis, we elucidated the mechanisms by which D7 promotes osteogenesis and inhibits osteoclastogenesis. MethodsThe affinity of D7 peptide towards calvarial OPCs and BMMs was investigated using fluorescence cytochemistry. The roles of D7 in osteogenesis and osteoclastogenesis by regulating redox balance was confirmed by cell counting kit-8, special stain assays (alkaline phosphatase stain, alizarin red stain and tartrate‐resistant alkaline phosphatase stain), fluorescence cytochemistry, western blotting, quantitative real-time polymerase chain reaction. ResultsThe results demonstrated that D7 promoted the osteogenesis of calvarial OPCs by upregulating the expression of osteogenic differentiation factors. In contrast, D7 inhibited osteoclast differentiation and resorption by downregulating the expression of osteoclast phenotype marker. We further identified that these phenomenons may be due to the suppressive effect of D7 on reactive oxygen species production and the enhancing effect on antioxidant expression in both OPCs and BMMs, thereby regulating the redox balance of bone remodeling.ConclusionsCyclic peptide D7 could maintain bone homeostasis by regulating redox balance and provide a potential approach to strengthen the skeletal fitness of soldiers and prevent the occurrence of bone metabolic diseases.