The recombinant Link module of human TSG-6 suppresses cartilage damage in models of osteoarthritis: a potential disease-modifying OA drug
Drummond SP., Bartnik E., Kouvatsos N., Scott JL., Dyer DP., Thomson JM., Price AJ., Anand S., Biant LC., Leeuw T., Herrmann M., Milner CM., Day AJ.
ABSTRACTObjectivesTo investigate the role of endogenous TSG-6 in human osteoarthritis (OA) and assess the disease-modifying potential of a TSG-6-based biological treatment in cell, explant and animal models of OA.MethodsKnee articular cartilages from OA patients were analysed for TSG-6 protein and mRNA expression using immunohistochemistry and RNAscope, respectively. The inhibitory activities of TSG-6 and its isolated Link module domain (Link_TSG6) on cytokine-induced glycosaminoglycan loss in OA cartilage explants were compared. Mesenchymal stem/stromal cell (MSC)-derived chondrocyte pellet cultures were used to determine the effects of Link_TSG6 and full-length TSG-6 on IL-1α-, IL-1β- or TNF-stimulated ADAMTS4, ADAMTS5 and MMP13 mRNA expression. Link_TSG6 was administered i.a. to the rat ACLTpMMx model and cartilage damage and tactile allodynia were assayed.ResultsTSG-6 is predominantly associated with chondrocytes in regions of cartilage damage and its expression is negatively correlated with MMP13, the major collagenase implicated in OA progression. Link_TSG6 is more potent than full-length TSG-6 at dose-dependently inhibiting cytokine-mediated matrix breakdown in human OA cartilage explants; about 50% of donor cartilages, from 59 tested, were responsive to Link_TSG6 treatment. Similarly, Link_TSG6 displayed more potent effects in 3D pellet cultures, suppressing aggrecanase and collagenase gene expression. Link_TSG6 treatment reduced touch-evoked pain and dose-dependently inhibited cartilage damage in a rodent model of surgically-induced OA.ConclusionsNative TSG-6 is associated with a low catabolic chondrocyte phenotype in OA cartilage. Link_TSG6, which has enhanced chondroprotective activity compared to the full-length TSG-6 protein, demonstrates potential as a disease modifying OA drug (DMOAD) and warrants further investigation and development.KEY MESSAGESWhat is already known about this subject?TSG-6, a protein with anti-inflammatory and protective effects in other tissues, is expressed in joints affected by osteoarthritis – a condition for which there are no disease-modifying drugs.What does this study add?A novel protective mechanism has been identified, whereby TSG-6 inhibits inflammatory cytokine-induced catabolic pathways in cartilage.The Link module of TSG-6 (Link_TSG6) has been shown to have greater potency than TSG-6 as an inhibitor of cartilage damage and is efficacious in a rat model of osteoarthritis.Data from cartilage explants indicate that OA patients can be stratified for Link_TSG6 responsiveness.How might this impact on clinical practice or future developments?Link_TSG6 has been identified as potential disease-modifying OA drug that mimics an intrinsic protective process.