| The treatment of osteoarthritis(OA)has become a worldwide problem due to the poor regeneration capability of articular cartilage which is a non-vascular tissue composed of a highly dense matrix and sparse chondrocytes.It is reported that the effect of MSC-based therapy was attributed to paracrine mechanism.As a complete component of cell-to-cell communication,the role of extracellular vesicles,especially exosomes in cellular microenvironment has been paid more and more attention.Bone marrow mesenchymal stem cells(BMSCs)can secrete different bioactive factors and signals in response to different microenvironment.Kartogenin(KGN)is a new non-protein heterocyclic compound which could enhance the interaction between BMSCs and chondrocytes,and promote the formation of cartilage.The effect of KGN on the secretion of BMSCs in the repair of cartilage regeneration requires further study.In this study,exosomes from BMSCs(BMSC-Exos)and KGN induced exosomes from BMSCs(KGN-BMSC-Exos)were extracted and identified.Then,we studied the role of BMSC-Exos and KGN-BMSC-Exos in cartilage repair.In vitro,we found that both exosomes could be internalized by chondrocytes,promoted the chondrocytes migration and stimulated chondrocytes proliferation in a dose-dependent manner.Meanwhile,the expression of lubricin,glycosaminoglycan(GAGs)and COL II in chondrocytes were significantly improved by the two kinds of exosomes.The expression of lubricin and COL II in chondrocytes of KGN-BMSC-Exos group was significantly higher than those of BMSC-Exos group,while the expression of GAGs was lower than that of BMSC-Exos group.It was also found that both BMSC-Exos and KGN-BMSC-Exos advanced the expression of SOX-9,COL2A1,Prg4 and Agg,depressed the expression of C-myc and Adamts5,which could increase the accumulation of cartilage matrix.At the same time,the decreased expression of IL-1β which played an important role in preventing articular cartilage degeneration and alleviating the process of OA.The effect of KGN-BMSC-Exos was better than that of BMSC-Exos.In addition,BMSC-Exos inhibited the expression of Run X 1 and KGN-BMSC-Exos restored and enhanced the expression of Run X 1,which was beneficial to the formation and maintenance of hyaline cartilage.In addition,BMSC-Exos and KGN-BMSC-Exos had little effect on COL1A1,which showed that both exosomes could maintain the differentiation phenotype of chondrocytes.The above results from the molecular level indicated that both BMSC-Exos and KGN-BMSC-Exos could promote the metabolic activity of chondrocytes,in which the KGN-BMSC-Exos effect is better.In vivo,we encapsulated two kinds of exosomes in Col-Tgel hydrogel and transplanted them into cartilage defects of SD rats.The results showed that the cartilage repair was almost completed in KGN-BMSC-Exos group at 6th week.Hyaline cartilage formation was observed,and the boundary between new cartilage tissue and subchondral bone was obvious.The cartilage defects repair in the other groups were was later than that in the KGN-BMSC-Exos group.Furthermore,BMSC-Exos and KGN-BMSC-Exos could promote the expression of GAGs,lubricin and COL II proteins in vivo,and KGN-BMSC-Exos had better effect.These results indicated that the exosomes produced by KGN treatment had more significant effect on cartilage repair.It is proved that the pretreatment of MSCs by small molecules can improve the performance of exosomes tissue repair to a certain extent,which provides a basis for the application of exosomes in tissue regeneration and repair in the future. |
