Synovial mesenchymal stem cell-derived exosomes delivering GRPEL1 activate PINK1-mediated mitophagy to promote cartilage repair in arthritis

Figure 4 GrpE-like 1 was upregulated in human synovial mesenchymal stem cells-derived exosomes. A: Transmission electron microscopy with uranyl acetate negative staining reveals the morphological characteristics of exosomes (Exos) across different groups, displaying their typical cup-shaped or spherical structure; B: Nanoparticle tracking analysis using a nanoparticle tracking analyzer and dedicated software precisely determines the diameter distribution of Exos in each experimental condition, providing insights into their size homogeneity; C: Western blot analysis confirms Exo identity by demonstrating the protein levels of canonical exosomal markers CD63, CD9, and tumor susceptibility gene 101 across the different experimental groups, validating Exo purity and integrity; D: Quantitative real-time polymerase chain reaction analysis of GrpE-like 1 mRNA expression levels in Exos from each experimental group, revealing potential genetic cargo variations; E: Western blot evaluation of GrpE-like 1 protein expression in Exos, complementing the mRNA analysis and providing a comprehensive molecular characterization of the exosomal GrpE-like 1 content. ^bP < 0.01 vs Exo-oeNC; ^dP < 0.01 vs Exo-siNC. Exo: Exosome; SMSC: Synovial mesenchymal stem cells; TSG101: Tumor susceptibility gene 101; GRPEL1: GrpE-like 1.