MSC-derived miR-181b Overexpressing Exosomes Enhanced Osteointegration by Enhancing M2 Polarization of Macrophages via Targeting the PRKCD/AKT Pathway

Abstract Background: Many patients suffer from implant loosening after the implantation of titanium alloy caused by immune response to the foreign bodies and this could inhibit osteogenesis, which could possibly give rise to poor osteointegration and there is currently no appropriate solution in clinical practice. Exosomes overexpressing miRNA has been proven to be a suitable candidate for solving this problem. In this study, we explored whether miR-181b could exert beneficial effect on promoting M2 macrophage polarization, thus inhibiting inflammation as well as promoting osteogenesis and elaborated the underlying mechanism in vitro . Furthermore, we aimed to find whether exosomes overexpressing miR-181b (Exo-181b) could enhance osteointegration in vivo . Methods: In vitro and in vivo studies were carried out for assessing the anti-inflammatory and pro-osteogenesis effect of miR-181b. In vitro , ELISA was applied for the detection of the inflammation factors levels including IL-6, TNF-α, as well as IL-10 and the percentage of M1 or M2 polarization was determined by flow cytometry. Also, qRT-PCR was used for the detection of the relative gene expression of the CCR7, CD206, Arg-1, iNOS, VEGF and BMP-2 genes. Western blotting was applied for detecting the protein expression of PRKCD, AKT and p-AKT. In vivo , we established air pouch model for evaluating the effect of Exo-181b on macrophage polarization and distal femoral bone defect model was established for determining the osteointegration effect of Exo-181b by MicroCT, sequential fluorescent labeling and histological analysis. Results: In vitro , we firstly verified that miR-181b significantly enhanced M2 polarization and inhibited inflammation by suppressing PRKCD and activating p-AKT. Then, in vivo , we verified that Exo-181b enhanced M2 polarization, reduced the inflammatory response and enhanced osteointegration. Conclusions: MiR-181b could suppress inflammatory response by regulating the PRKCD/AKT signaling pathway and promoting M2 polarization, which further promoting osteogenesis of hBMSC in vitro and Exo-181b could promote osteointegration in vivo .