| Osteoarthritis(OA)is the most prevalent arthritic disease,and is characterized by the progressive destruction of articular cartilage,swelling of synovium and remodeling of the underlying bone in the synovial joints.Pain,joint dysfunction and deformity are its major clinical features,and can affect the normal function of the knee,hip,spine and fingers.The current therapies for OA mainly focus on pain suppression,viscosupplementation(intra-articular injections of hyaluronic acid)and joint replacement.But none of these methods fundamentally inhibit pathological aggravation of OA.The development of biomaterials and regenerative medicine bring great gospel to the treatment of OA.However,without fine targeting to the exacerbation of OA progression or resistance to the inflammatory environment,the current biomaterials couldn't treat OA ideally.The pathological progression of OA involves a complex process of loss of joint function,in the development of which inflammation plays a critical role.Current studies show that OA progression can be divided into 4 stages: Stage 1.Cartilage surface defects,lubrication function weakens,and cartilage matrix erodes;Stage 2.Matrix erosion makes immune cells secrete proinflammatory cytokines,forming inflammatory microenvironment;Stage 3.Inflammatory stimulation causes many tissues to dissimilate,and secrete a large number of proinflammatory cytokines and matrix-degrading enzymes,forming a positive feedback pathway,rendering a substantial matrix loss;Stage 4.With further aggravation of the inflammatory microenvironment,a variety of tissue complications begin to appear,and subchondral bone starts to reconstruct,leading to the loss of basic mechanics.Therefore,in order to inhibit the pathological increase of OA,we must first find the specific characteristics of the conversion of various stages of OA lesions,and then use biological materials targeting these specific lesions to cure OA.It is actually based on the above-mentioned ideas that we performed the following research.First,we used immune cells,synovial inflammatory cells and chondrocytes,combined with hydrogel and tissue co-culture techniques,to construct an inflammatory model which modeled early,progressive,and late inflammatory status respectively.We named this model EPL-OA model in vitro.By studying the biological characteristics of this model,including the detection of the formation of inflammatory microenvironment,and the changes of the anabolic and catabolic pathways in tissues,we were able to use this model to explore the specific lesion characteristics of OA phase transformation.Meanwhile,this model also provided a good platform for testing the effect of biomaterials in OA treatment.By studying the early OA model,we found the release of intermittent inflammatory cytokines couldn't generate an inflammatory microenvironment at the early stage of OA(Stage 1),so we could avoid the immune activation due to wear and tear by resuming lubrication.Based on the mechanism of natural joint lubrication system,a HPX biomimetic synovial fluid system was constructed,which was composed of hyaluronic acid(HA)-based hydrophilic secondary brush polymer(HPA,1.0 mg/m L)and amphiphilic secondary brush polymer(HPM,0.20 mg/m L).This system directly modeled the superficial network of cartilage surface in the natural lubrication mechanism.Friction coefficient assay on normal and impaired friction pair suggested HPX synovial fluid had a 15-26% improvement in natural cartilage lubrication compared with commonly used HA for joint injection.At the same time,HPX synovial fluid didn't have side effects on cartilage and synovial tissues,including cytotoxicity,inflammatory response and hyaline cartilage dissimilation.These finding suggested HPX synovial fluid system could treat early OA by inhibiting the exacerbation of OA from Stage 1 to Stage 2.According to the studies of progressive and late OA models,we found inflammatory microenvironment destroyed the balance of anabolic and catabolic pathways of cartilage in the model,suggesting it might be possible to block the exchange of proinflammatory cytokines between tissues,inhibiting the exacerbation of OA from Stage 2 to Stage 3.We co-cultured the HPX biomimetic synovial fluid system with the EPL-OA model in vitro,and determined the stability of HPX biomimetic synovial system in the inflammatory environment and its effect on the inflammatory microenvironment of the model.We found synovial fluid system maintained good stability and lubrication in the early and progressive OA model,but lost function rapidly in the late OA model.Meanwhile,HPX synovial fluid system could significantly reduce the concentration of the proinflammatory cytokines in the OA model and alleviate the degradation of cartilage matrix in the model,producing certain effect on inhibition of inflammatory aggravation.These findings indicated blocking the exchange of signals between inflammatory tissues was effective to inhibit the exacerbation of OA from Stage 2 to Stage 3.In addition to blocking the exchange of inflammatory cytokines,the introduction of a device capable of regenerating chondrocytes(new matrix secretion)could effectively suppress the aggravation of OA from Stage 2 to Stage 3,so we constructed a hydrogel with cartilage regeneration and anti-inflammatory abilities.We used modified glucosamine as the active site to prepare a glycosaminoglycan-modified polyethylene glycol(PEG-g-GA)hydrogel which could be coated with stem cells.Both in vitro and in vivo experiments demonstrated PEG-g-GA hydrogel could induce coated bone marrow mesenchymal stem cells to differentiate into hyaline cartilage,and in the meantime,it had some antiinflammatory ability.These findings confirmed PEG-g-GA hydrogel could inhibite the aggravation of OA from Stage 2 to Stage 3.Finally,according to the studies of EPL-OA model,to inhibit the aggravation of OA from Stage 3 to Stage 4,we required a material support with good basic mechanical support,and at the same time lubrication and biocompatibility were considered.So we optimized the-TCP blending P VA system and prepared an integrated repair gel with the density upper layer and the porous lower layer.As well as having good tensile and compressive properties,the upper layer of the gel had good lubrication property and the ability of effective attachment to cartilage cells,and the porous structure of lower layer could better induce mesenchymal stem cells to differentiate into osteoblasts,thereby forming good mechanical support.In summary,our studies used hydrogel-tissues co-culture technology to construct the EPL-OA model to simulate the pathological process of OA.This model plays a vital role in exploring the lesions of various stages of OA,guiding the OA therapy with biomaterials and testing the therapeutic effects of drugs and materials.Based on the findings from this model,we proposed new strategies to inhibit the progression of OA to the late period.Empirical experimentations were also conducted,by using HPX synovial fluid system,PEG-g-GA gel,and-TCP / PVA double layer integrated gel respectively,to find out their different effectiveness in blocking the progression of OA to the late period as well as their effectiveness in the functional recovery,thus providing valuable reference for the effective treatment of OA. |
PDF Full Text Request