Research On Collagen-based Materials Used In The Repair Of Articular Cartilage Damage

Articular cartilage(AC)has a limited intrinsic healing capacity due to its structure and functional characteristics.AC regeneration is still a big challenge in clinical and in regenerative medicine.Due to the good biocompatibility,collagen is widely applied as scaffold in the research of AC repair and as the carrier of a variety of bioactive molecules.Recently,we constructed a collagen-based targeted delivery system of fibroblast growth factor 2(FGF2)to subchondral bone(SB).We found that FGF2 could modulate the SB,up-regulate bone morphogenetic protein(BMP)signal pathway and promote the regeneration of both the cartilage and SB.However the neo-cartilage integration still requires improvement.By using insulin like growth factor 1(IGF-1)loaded collagen matrix,we found high-dose IGF-1 was beneficial to the neo-cartilage formation and integration,therefore enhanced the repair of AC defect.However,the high-dose IGF-1 was not beneficial to the SB formation.Accordingly,we speculate that FGF2 and IGF-1 might play complement roles in promoting the regeneration of cartilage and SB as well as the neo-cartilage integration.Therefore,in this study,a collagen-based tissue selective delivery system of FGF2 and IGF-1 was constructed.The in vitro and in vivo release of FGF2 and IGF-1 were determined.Subsequently,the effect and the mechanism of this newly constructed collagen-based material on the repair of full-thickness AC defect were investigated.On the other hand,although IGF-1 shows chondral-protective effect during AC injury,it has no effect on promoting the migration of the injury-surrounding chondrocyte to enhance the repair.Thus,we performed a preliminary exploration on the effect of Galectin 3(Gal3),which can promote cells migration,on the AC injury.Furthermore,a collagen terminal binding peptide(CTBP)modified collagen matrix was constructed,and the effect of this collagen-based material on chondrocyte was investigated in vitro.The main findings and conclusions of this work are as follows:1.By using a double-layered collagen membrane with the dense layer and loose layer,a tissue selective delivery system of FGF2 and IGF-1 was constructed,of which FGF2 was adsorbed on the loose layer,while IGF-1 on the dense layer.Both the in vitro and in vivo release behaviors of FGF2 and IGF-1 showed a directional way.FGF2 was released from the loose layer without penetrating to the dense layer side,while IGF-1 from the dense layer without to the loose layer.These results suggested that the growth factors might be released in a tissue selective delivery manner after membrane implantation into the full-thickness AC defect,to cartilage or SB,respectively.This newly constructed collagen-based material induced different gene expression profiles compared with the control group.Particularly,this delivery system promoted the regeneration of both cartilage and SB,and improved the neo-cartilage integration.2.We found that Gal3 could promote the chondrocyte migration from the explant in vitro.However,Gal3 showed no effect on chondrocyte proliferation,while it downregulated the type ? collagen expression of chondrocyte.Particularly,Gal3 upregulated the expression of matrix metalloproteinase 13(MMP13),indicating that it might increase the degradation of matrix to promote the cell migration.By implanting a Gal3-loaed collagen-based membrane into the AC defect,we found the expression of MMP13 of the cartilage was upregulated.The number of cells and the concentration of interleukin-1?(IL-1?)in the synovial fluid of Gal3 group were significantly increased.Meanwhile the inflammatory response of the synovial membrane of Gal3 group was obvious.These results indicated that Gal3 should not be used for AC repair;it might promote the development of inflammation.3.It was found that CTBP hindered the formation of collagen fibers by specific interaction with the terminal peptide of collagen.The two-arm PEG derivatives of collagen terminal peptides(CTBP-PEG-CTBP)bind to collagen fibers to promote the orderly arrangement of collagen fibers to some extent.Preliminary studies have also found that CTBP-PEG-CTBP modified collagen materials promoted proliferation and phenotype maintenance of chondrocytes in vitro.To sum up,this project investigated the function and mechanism of several biomolecular loaded or modified collagen materials in articular cartilage injury and repair.We have found that tissue selective delivery of FGF2 and IGF-1 collagen materials can synergistically promote regeneration of cartilage and subchondral bone,and improve the integrity of neo-cartilage,which has potential application in repair of articular cartilage injury.Although Gal3 promoted the migration of chondrocytes,but also promoted degradation of extracellular matrix and increase the content of inflammatory molecules,suggesting that Gal3 cannot repair the cartilage damage,but may be a target for the treatment of articular cartilage injury.The collagen matrix materials modified by CTBP derivatives formed a relatively orderly structure showed good cellular compatibility that by promoting the proliferation and phenotype maintenance of chondrocytes,which provides a new idea for the construction of new ordered structure collagen matrix materials.Our findings may advance the understanding of mechanism of the AC injury and the repair,and may helpful in the development of collagen-based materials.