Bone is crucial for supporting the body, protecting other organs, providing minerals, and secreting hormone to regulate other organs function. to cell therapy with MSCs in regenerative medicine. Here, we review the current knowledge of EV and spotlight the application studies of MSCs-EV in bone disorders by focusing on osteoarthritis (OA), rheumatoid arthritis (RA), osteoporosis (OP), and bone fracture. Moreover, we discuss the key issues and perspectives of MSCs-EV as a clinical therapeutic strategy for bone diseases. in polymer nets (Gurunathan et al., 2019). Because it is usually easily operated and 3′-Azido-3′-deoxy-beta-L-uridine does not require specialized gear, precipitation allows to be integrated into clinical usage and it can be applied for large sample sizes (Konoshenko et al., 2018). The disadvantage of this method is usually that there is no specificity for non-exosomal material, such as protein aggregates, which may be co-isolated with the exosomes resulting in low purity (Peterson et al., 2015). In addition, polymer-based precipitation is also used for EV isolation based on the changes in EV solubility and/or aggregation (Zeringer et al., 2015). offers a proprietary reagent named ExoQuick, which can be used to purify exosomes from a wide variety of tissue culture media, and certain biofluids3. In order to isolate more specific EV populations, immunological methods are used based on highly specific interactions with the molecules (e.g., lipids, proteins, and polysaccharides) uncovered around the EV surface. This approach is particularly useful when the protein expressed around the EV surface lacks a soluble counterpart (Gurunathan et al., 2019). Immuno-affinity is simple, rapid, and compatible with the laboratory gear, while it is usually unstable and not suited for isolating EV from large quantities of biological samples (Konoshenko 3′-Azido-3′-deoxy-beta-L-uridine et al., 2018). Moreover, a new method utilizing aqueous two-phase system is usually adopted to isolate high-purity EV by preventing the protein contamination in the EV fraction (Kim et al., 2015). Recently, microfluidics-based technologies have become a pattern for EV isolation, especially for microscale isolation, detection, and analysis of exosomes (Konoshenko et al., 2018; Gurunathan et al., 2019). Microfluidic devices utilizes the usual separation determinants and innovative sorting principles, mainly including: (a) trapping exosomes with an immune-affinity approach (microfluidic chip, Exochip, magnetic capture beads) (Chen C. et al., 2010; Kanwar et al., 2014; Shao et al., 3′-Azido-3′-deoxy-beta-L-uridine 2015); (b) membrane-based filtration (double filtration) (Liang et al., 2017); (c) trapping exosomes on porous structures (nanowire micropillars) (Wang et al., 2013); (d) acoustics (acoustic nano-filter system); (e) lateral displacement (nanoscale lateral displacement arrays) (Wunsch et al., 2016); and (f) viscoelastic flow (field-free microfluidic sorting) (Zhou J. et al., 2019). Open in a separate window Physique 3 The diagram of the MSCs-EV preparation and the therapeutic effects of MSCs-EV on osteoarthritis (OA), rheumatoid arthritis (RA), osteoporosis (OP) and bone fracture. TABLE 1 The isolation techniques of EV and their advantages and disadvantages. by re-establishing chondrocyte homeostatic state, protecting chondrocytes from apoptosis and stimulating macrophage polarization toward anti-inflammatory phenotype. Therefore, MSCs-EV possess the immunomodulatory properties and accelerate the recovery of cartilage and joint in OA. Cartilage Protection and Regeneration Effect of MSCs-EV in OA The main pathology of early stage OA is the degeneration of chondrocytes, resulting in damage to articular cartilage. Metabolic and structural changes in articular cartilage play a major role in the initiation and progression of OA. MSCs-EV exert important therapeutic effect on OA by protecting cartilage from degradation and promoting cartilage regeneration, which is now the focus of clinical therapy. The efficacy of hESC-MSCs-exosomes (a modal size of 100 nm) on cartilage repair was firstly reported in 2016 (Zhang S. et al., 2016). After treatment with exosomes, the rat model of osteochondral defect displayed almost complete neotissue coverage with good surface regularity and complete integration with the surrounding cartilage. hESC-MSCs-exosomes accelerated neotissue filling and enhanced matrix Mouse monoclonal to GATA1 synthesis of type II collagen and s-GAG, demonstrating the capacity of MSCs-exosomes in cartilage repair and regeneration (Zhang S. et al., 2016). It has also been exhibited that MSCs-EV safeguard chondrocytes from apoptosis, balance the anabolic and catabolic processes and re-establish chondrocyte homeostatic state via balancing the synthesis and degradation of cartilage matrix, thus safeguard cartilage and bone from degradation (Cosenza et al., 2017; Wang et al., 2017; Wu et al., 2019). All these observations demonstrate the therapeutic effects of MSCs-EV on.