Cyclic strain‐induced chondrocyte damage is actively involved in the pathogenesis of osteoarthritis and arthritis. MicroRNAs (miRNAs) carried by exosomes have been implicated in various diseases. However, the role of miR‐100‐5p in cyclic strain‐induced chondrocyte damage remains to be elucidated. miR‐100‐5p and NADPH oxidase 4 (NOX4) were silenced or overexpressed in human primary articular chondrocytes. PKH‐67 Dye was used to trace exosome endocytosis. Reactive oxygen species (ROS) production was monitored using DCFH‐DA. Cell apoptosis was measured using a flow cytometer. Quantitative RT‐PCR and Western blots were used to evaluate gene expression. Cyclic strain promoted ROS production and apoptosis in primary articular chondrocytes in a time‐dependent manner. HucMSCs‐derived exosomal miR‐100‐5p inhibited cyclic strain‐induced ROS production and apoptosis in primary articular chondrocytes. miR‐100‐5p directly targeted NOX4. Overexpressing NOX4 attenuated hucMSCs‐derived exosomes‐mediated protective effects in primary articular chondrocytes. Cyclic strain promotes ROS production and apoptosis in primary articular chondrocytes, which was abolished by hucMSCs‐derived exosomal miR‐100‐5p through its target NOX4. The findings highlight the importance of miR‐100‐5p/NOX4 axis in primary articular chondrocytes injury and provide new insights into therapeutic strategies for articular chondrocytes injury and osteoarthritis.
Background
Rotator cuff injury is the most common cause of shoulder disability, and although the repair technique has improved, the rate of rotator cuff reduction after repair is still high. The fibrocartilage region, which appears to be histologically inserted, cannot be regenerated. In recent years, studies have reported that mesenchymal stem cells (MSCs) have enhanced cartilage regeneration in the tendon and bone interface after rotator cuff repair, which has become a hot topic of research.
Material/Methods
Two mesenchymal stem cell types, SMSC (synovial-derived mesenchymal stem cells) and BMSC (bone marrow-derived mesenchymal stem cells) were intervened using kartogenin (KGN). The cytotoxicity was evaluated and the proliferation of the 2 cells was observed. Four commonly used cartilage phenotype genes were detected by quantitative real-time polymerase chain reaction, and the cartilage differentiation of MSCs induced by KGN was explored. The bidirectional regulation of the expression of BMP-7 and the downstream gene Smad5 was observed by constructing a lentiviral overexpression vector containing the target gene BMP-7. To explore whether BMP-7/Smad5 pathway activation promotes differentiation of SMSCs into chondrocytes.
Results
KGN can induce the selective differentiation of endogenous MSCs into chondrocytes by activating the BMP-7/Smad5 pathway, which promotes the regeneration of interfacial cartilage, and improves the quality of tendon healing of the tendon after rotator cuff repair.
Conclusions
This study found a new biological intervention method to promote the effect of tendon on bone healing after rotator cuff repair.
The communication between macrophages and tendon cells plays a critical role in regulating the tendon-healing process. However, the potential mechanisms through which macrophages can control peritendinous fibrosis are unknown. Our data showed a strong pro-inflammatory phenotype of macrophages after a mouse tendon–bone injury. Moreover, by using a small-molecule compound library, we identified an aldehyde dehydrogenase inhibitor, disulfiram (DSF), which can significantly promote the transition of macrophage from M1 to M2 phenotype and decrease macrophage pro-inflammatory phenotype. Mechanistically, DSF targets gasdermin D (GSDMD) to attenuate macrophage cell pyroptosis, interleukin-1β, and high mobility group box 1 protein release. These pro-inflammatory cytokines and damage-associated molecular patterns are essential for regulating tenocyte and fibroblast proliferation, migration, and fibrotic activity. Deficiency or inhibition of GSDMD significantly suppressed peritendinous fibrosis formation around the injured tendon and was accompanied by increased regenerated bone and fibrocartilage compared with the wild-type littermates. Collectively, these findings reveal a novel pathway of GSDMD-dependent macrophage cell pyroptosis in remodeling fibrogenesis in tendon–bone injury. Thus, GSDMD may represent a potential therapeutic target in tendon–bone healing.
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