Articular cartilage defects are one of the most challenging issues in orthopedic disorders.Despite the current cell/stem cell-based therapies, still there are some fundamental challenges in theregeneration of cartilage defects. Limited chondrogenic responses following cell transplantation could bethe major barrier ot stem cell therapy in orthopedic disorders. Currently, the MSCs-derived extracellularvesicles (MSCs-EVs) have provided a promising alternative to the perspective of regenerative cartilagerepair. Those natural nano-carriers work as one of the main transporters of proteins, miRNAs, and smallmolecules (SMs). Clinical application of EVs for targeted therapies has shown a beneficial outcome incases with articular cartilage defects. Also, the results of several studies, both in vitro and in vivo, havepointed to
Kartogenin (KGN) as one of the strongest SMs for the induction of chondrogenesis. Here, wehave hypothesized that EVs-loaded KGN would be an effective approach for chondrogenesis followingcartilage defects. Thus, the main objectives of this study are to use EVs for safe drug delivery, therebyproviding more effective and long-lasting improvements in chondrogenesis in vitro, and to betterunderstand the efficacy and long-term stability of EVs as SM carriers in vivo.Material and Method: Human bone marrow-derived MSCs (hBM-MSCs) were obtained from theATMP Center at the Royan Institute, Tehran, Iran. Following the characterization of the cells through invitro osteogenic/adipogenic/chondrogenic differentiation assay and qRT-PCR, they were expandedutilizing αMEM media containing ۱۵% FBS. The MSCs-derived extracellular vesicles (EVs) were alsoprovided by the ATMP center of the Royan Institute through a differential ultracentrifuge under ۱۰۰,۰۰۰g at ۷۰ min. The molecular phenotype of the purified EVs was identified by western-blot assay and also aseries of electron-microscopy and DLS evaluations were subsequently done for size and shape analysis.The cellular uptake of Calcein AM-labeled EVs was assessed on the PKH۲۶-labeled MSCs under thefluorescent microscope at ۰ and ۲۴ hours post-treatment with EVs. The KGN loading into the EVs hadbeen provided by the sonication method and encapsulation efficiency was estimated by spectrophotometry. Compared with the chondrogenic media, the in vitro chondrocyte differentiationpotential of KGN and KGN-EVs treated hBM-MSCs were evaluated in a ۳D cell culture context. Thehistological characteristics of the differentiated hBM-MSCS spheroids were performed through Toluidineblue, Safranin O, and Alcian blue staining at ۷ and ۱۴ days post-intervention. Ultimately, using qRT-PCRanalysis, the expression rate of the collagen II, aggrecan, and collagen X genes in all three groups wereevaluated at ۱۴ days of intervention compared with undifferentiated hBM-MSCs.