Study On The Immunoregulation Mechanism Of Cartilage Extracellular Matrix And In Vivo Study Of Combination With Interleukin 4 To Promote Osteochondral Repair

Background: Cartilage regeneration is a complex pathophysiologic process.Synovial macrophages play an important immunomodulatory role in the acute inflammation around joint injury.Due to the difference and heterogeneity of macrophages,the polarization of macrophages is a key factor in determining the healing response after cartilage injury.Biomaterials derived from the extracellular matrix have been used to repair and rebuild various tissues by regulating the response of host macrophages.However,the immunomodulatory effect of decellularized cartilage extracellular matrix(ECM)on macrophages has not been well elucidated.Thus,clarifying the immunomodulatory properties of decellularized cartilage matrix(DCM)has important guiding significance for the design of cartilage regeneration materials.Methods: The DCM derived from porcine articular cartilage was prepared by wet pulverization + differential centrifugation,and its composition was determined by histological staining and proteomics.The responses of mouse macrophage cell line RAW264.7 and mouse bone marrow-derived macrophages(BMDMs)to pepsinsolubilized DCM(PDCM)were tested in vitro.Then the effect of PDCM activated macrophage supernatant on the invasion,migration,proliferation and chondrogenesis of bone marrow mesenchymal stem cells(BMSCs)were detected.Finally,we used the rat knee trochlear osteochondral defect model to explore the effectiveness of continuous injection of IL-4 into the articular cavity in the early stage of implantation(3-7 days)combined with the autoimmune regulatory properties of decellularized DCM scaffold to achieve cartilage regeneration.Results: The prepared DCM had no residual cellular components,and retained the main components of natural cartilage extracellular matrix.Macrophages are activated by PDCM and polarized into a unique subtype related to the anti-inflammatory and pro-regeneration.And PDCM-polarized macrophages supernatant could promote BMSCs invasion,migration,proliferation and cartilage differentiation in vitro.In vivo experiments showed that the cell-free DCM scaffold combined with IL-4 precisely regulated and optimized the immune response,and promoted the effective regeneration of articular cartilage.Conclusion: Decellularized cartilage extracellular matrix is a good cartilage tissue engineering material.The active regulation of macrophage phenotype by this material is one of its mechanisms to promote cartilage regeneration and repair.This decellularized cartilage extracellular matrix scaffold combined with a precise active immune regulation strategy provides a new approach for the development of cartilage regeneration materials.