Extracellular vesicles derived from neural EGFL-Like 1-modified mesenchymal stem cells improve acellular bone regeneration via the miR-25-5p-SMAD2 signaling axis.

Stem cell based transplants effectively regenerate tissues; however, limitations such as immune rejection and teratoma formation prevent their application. Extracellular vesicles (EVs)-mediated acellular tissue regeneration is a promising alternative to stem cell based transplants. Although neural EGFL-like 1 (Nell1) is known to contribute to the osteogenic differentiation of bone marrow stem cells (BMSCs), it remains unknown whether EVs are involved in this process. Here, we present that EVs derived from Nell1-modified BMSCs (Nell1/EVs) have a stronger ability to promote BMSC osteogenesis owing to miR-25-5p downregulation. MiR-25-5p inhibits osteogenesis by targeting Smad2 and suppressing the SMAD and extracellular signal-related kinase 1 and 2 (ERK1/2) pathway activation. In addition, we demonstrate that the 3D-Nell1/EV-hydrogel system is beneficial for bone regeneration in vivo, probably stemming from a slow, continuous release and high concentration of EVs in the bone defect area. Thus, our results have shown the potential of Nell1/EVs as a novel acellular bone regeneration strategy. Mechanistically, the identification of miR-25-5p-SMAD2 signaling axis expands the knowledge of Nell1/EVs induced osteogenesis.

Exosomes Enhance Adhesion and Osteogenic Differentiation of Initial Bone Marrow Stem Cells on Titanium Surfaces.

Successful osseointegration involves the biological behavior of bone marrow stem cells (BMSCs) on an implant surface; however, the role of BMSC-derived extracellular vesicles (EVs)/exosomes in osseointegration is little known. This study aimed to: (i) explore the interaction force between exosomes (Exo) and cells on a titanium surface; (ii) discuss whether the morphology and biological behavior of BMSCs are affected by exosomes; and (iii) preliminarily investigate the mechanism by which exosomes regulate cells on Ti surface. Exosomes secreted by rat BMSCs were collected by ultracentrifugation and analyzed using transmission electron microscopy and nanoparticle tracking analysis. Confocal fluorescence microscopy, scanning electron microscopy, Cell Counting Kit-8 (CCK-8), quantitative real-time polymerase chain reaction techniques, and alkaline phosphatase bioactivity, Alizarin Red staining, and quantification were used to investigate the exosomes that adhere to the Ti plates under different treatments as well as the morphological change, adhesion, spread, and differentiation of BMSCs. We found that exosomes were efficiently internalized and could regulate cell morphology and promoted the adhesion, spreading, and osteogenic differentiation of BMSCs. These were achieved partly by activating the RhoA/ROCK signaling pathway. Our discovery presents a new insight into the positive regulatory effect of exosomes on the biological behaviors of BMSCs on Ti surface and provides a novel route to modify the surface of a Ti implant.

NEMO­binding domain peptide ameliorates inflammatory bone destruction in a Staphylococcus aureus­induced chronic osteomyelitis model.

Osteomyelitis, which is characterized by progressive inflammatory bone destruction and resorption, is a difficult­to­treat infection. Staphylococcus aureus (S. aureus) is one of the major causes of this disease. This pathogenic microorganism possesses several characteristics, which facilitate its involvement in the occurrence and progression of osteomyelitis. A cell­permeable peptide inhibitor of the IκB kinase complex, the nuclear factor (NF)­κB essential modulator­binding domain (NBD) peptide, has been reported to block osteoclastogenesis and may be considered a potential strategy for preventing inflammatory bone resorption. However, it remains to be determined as to whether the NBD peptide can regulate inflammation and bone resorption in S. aureus­induced osteomyelitis. In order to investigate the role of NBD in S. aureus­induced osteomyelitis, the present study obtained the NBD peptide, and confirmed that it inhibited receptor activator of NF­κB ligand­induced osteoclastogenesis in vitro. Subsequently, a bone defect was generated and S. aureus was injected into the mandible of experimental animals, in order to establish an in vivo osteomyelitis model. The present study analyzed the following three experimental groups: Untreated, treated with debridement, and treated with debridement plus NBD peptide administration. The results revealed that treatment with the NBD peptide reduced the bone defect in a 3­dimensional manner, and reduced bone resorption. To the best of our knowledge, the present study is the first to demonstrate that, in a model of osteomyelitis caused by S. aureus, the NBD peptide serves a role in inhibiting osteolysis and promoting bone remodeling in the direction of osteogenesis. The effects were better than those produced by debridement alone, thus suggesting that it may have promising therapeutic potential in osteomyelitis.