MicroRNAs (miRNAs) interfere with translation of specific target mRNAs and are thought to thereby regulate many cellular processes. Recent studies have suggested that miRNAs might play a role in osteoblast differentiation and bone formation. Here, we identify a new miRNA (miR-2861) in primary mouse osteoblasts that promotes osteoblast differentiation by repressing histone deacetylase 5 (HDAC5) expression at the posttranscriptional level. miR-2861 was found to be transcribed in ST2 stromal cells during bone morphogenetic protein 2-induced (BMP2-induced) osteogenesis, and overexpression of miR-2861 enhanced BMP2-induced osteoblastogenesis, whereas inhibition of miR-2861 expression attenuated it. HDAC5, an enhancer of runtrelated transcription factor 2 (Runx2) degradation, was confirmed to be a target of miR-2861. In vivo silencing of miR-2861 in mice reduced Runx2 protein expression, inhibited bone formation, and decreased bone mass. Importantly, miR-2861 was found to be conserved in humans, and a homozygous mutation in pre-miR-2861 that blocked expression of miR-2861 was shown to cause primary osteoporosis in 2 related adolescents. Consistent with the mouse data, HDAC5 levels were increased and Runx2 levels decreased in bone samples from the 2 affected individuals. Thus, our studies show that miR-2861 plays an important physiological role in osteoblast differentiation and contributes to osteoporosis via its effect on osteoblasts.

The discovery of osteoinductivity of calcium phosphate (Ca-P) ceramics has set an enduring paradigm of conferring biological regenerative activity to materials with carefully designed structural characteristics. The unique phase composition and porous structural features of osteoinductive Ca-P ceramics allow it to interact with signaling molecules and extracellular matrices in the host system, creating a local environment conducive to new bone formation. Mounting evidence now indicate that the osteoinductive activity of Ca-P ceramics is linked to their physicochemical and three-dimensional structural properties. Inspired by this conceptual breakthrough, many laboratories have shown that other materials can be also enticed to join the rank of tissue-inducing biomaterials, and besides the bones, other tissues such as cartilage, nerves and blood vessels were also regenerated with the assistance of biomaterials. Here, we give a brief historical recount about the discovery of the osteoinductivity of Ca-P ceramics, summarize the underlying material factors and biological characteristics, and discuss the mechanism of osteoinduction concerning protein adsorption, and the interaction with different types of cells, and the involvement of the vascular and immune systems.

The purpose of this study was to investigate the effect of phase compositions of porous calcium phosphate (CaP) ceramics on their protein adsorption behaviors in vitro and osteoinductive potentials in vivo in mice. Under competitive conditions, a high adsorption of bone morphogenetic protein 2 (BMP-2) was observed at a high initial concentration of BMP-2 in the multi-protein solution on all the four types of ceramics, indicating their strong affinity for BMP-2. No significant difference in BMP-2 adsorption between the ceramics was noted, indicating that phase composition could have little influence on BMP-2 adsorption. After implantation into the thigh muscles of mice for 45 and 90 days, the histological and histomorphometric analyses showed that porous biphasic calcium phosphate (BCP) ceramic consisting of 30% hydroxyapatite HA and 70% tricalcium phosphate (β-TCP), i.e. BCP-2 had stronger osteoinductive ability than the other three groups of ceramics. The immunohistochemical staining showed the highest expression of BMP-2 and osteocalcin (OCN) in BCP-2 group. Osteoinduction of porous CaP ceramics might be influenced by the amount of BMP-2 present in the local microenvironment in the implant, which was regulated by the phase composition of the ceramics. BCP-2 promoted the highest expression of BMP-2 and then showed the strongest osteoinduction in mice.

BackgroundDiabetic nephropathy (DN) is the leading cause of end-stage renal failure worldwide. lncRNAs are demonstrated to improve the DN by changing the expression of miRNAs. This study was aimed to investigate the effect of lncRNA GAS5/miR-452-5p on the inflammation, oxidative stress and pyroptosis of high-glucose-induced renal tubular cells.MethodsHK-2 cells were induced by HG to simulate DN cells. RT-qPCR analysis confirmed the transfection effects and detected the expression of GAS5, NLRP3, caspase1, IL-1β, pro-caspase1, pro-IL-1β, GSDMD-N and miR-452-5p. Western blot analysis determined the protein expression of NLRP3, caspase1, IL-1β, pro-caspase1, pro-IL-1β and GSDMD-N. The expression of GSDMD-N was also verified by immunofluorescence. The levels of TNF-α, IL-6, MCP-1, ROS, MDA and SOD were measured by commercial assay kits, respectively. Dual-luciferase reporter assay indicated that GAS5 could combine with miR-452-5p.ResultsGAS5 expression was decreased in HG-induced HK-2 cells. GAS5 overexpression could decrease the levels of TNF-α, IL-6, MCP-1, ROS and MDA and increase the levels of SOD. Moreover, GAS5 overexpression suppressed the expression of NLRP3, caspase1, IL-1β and GSDMD-N, and the results of immunofluorescence verified the above results. miR-452-5p interference could cause the same changes as GAS5 overexpression for HG-induced HK-2 cells, and GAS5 inhibition could reverse the effect of miR-452-5p interference.ConclusionGAS5 overexpression inhibited the inflammation, oxidative stress and pyroptosis of HG-induced renal tubular cells by downregulating the expression of miR-452-5p.

A three-level hierarchical calcium phosphate/collagen/hydroxyapatite (CaP/Col/HAp) scaffold for bone tissue engineering was developed using biomimetic synthesis. Porous CaP ceramics were first prepared as substrate materials to mimic the porous bone structure. A second-level Col network was then composited into porous CaP ceramics by vacuum infusion. Finally, a third-level HAp layer was achieved by biomimetic mineralization. The three-level hierarchical biomimetic scaffold was characterized using scanning electron microscopy, energy-dispersive x-ray spectra, x-ray diffraction and Fourier transform infrared spectroscopy, and the mechanical properties of the scaffold were evaluated using dynamic mechanical analysis. The results show that this scaffold exhibits a similar structure and composition to natural bone tissues. Furthermore, this three-level hierarchical biomimetic scaffold showed enhanced mechanical strength compared with pure porous CaP scaffolds. The biocompatibility and osteoinductivity of the biomimetic scaffolds were evaluated using in vitro and in vivo tests. Cell culture results indicated the good biocompatibility of this biomimetic scaffold. Faster and increased bone formation was observed in these scaffolds following a six-month implantation in the dorsal muscles of rabbits, indicating that this biomimetic scaffold exhibits better osteoinductivity than common CaP scaffolds.