Inhibition of interleukin-17-induced effects in osteoarthritis - An in vitro study

Interleukin-17A (IL-17) is a pro-inflammator¬y cytokine, which has been reported to be increased in the joint of patients with OA. This study aimed to identify whether IL-17 or its receptors are expressed in the joints of OA patients and establish the effect of IL-17 in vitro on primary human chondrocytes and synovial fibroblasts from the joints of OA patients. We further studied whether any anti-inflammatory agents in current clinical use were able to reduce the effects of IL-17. We hypothesize that IL-17 stimulates the production of matrix degrading and inflammatory proteins by acting on IL-17 receptors on chondrocytes and synovial fibroblasts, which can be blocked by clinically used anti-inflammatory therapeutics

Interleukin-17 cytokines and receptors: potential amplifiers of tendon inflammation

Interleukin (IL)-17A, a pro-inflammatory cytokine that is linked to the pathology of several inflammatory diseases, has been shown to be upregulated in early human tendinopathy and to mediate inflammatory and tissue remodelling events. However, it remains unclear which cells in tendons can respond to IL-17A, and how IL-17A, and its family members IL-17F and IL-17AF, can affect intracellular signalling activation and mRNA expression in healthy and diseased tendon-derived fibroblasts. Using well-phenotyped human tendon samples, we show that IL-17A and its receptors IL-17RA and IL-17RC are present in healthy hamstring, and tendinopathic and torn supraspinatus tendon tissue. Next, we investigated the effects of IL-17A, IL-17F, or IL-17AF on cultured patient-derived healthy and diseased tendon-derived fibroblasts. In these experiments, IL-17A treatment significantly upregulated IL6, MMP3, and PDPN mRNA expression in diseased tendon-derived fibroblasts. IL-17AF treatment induced moderate increases in these target genes, while little change was observed with IL-17F. These trends were reflected in the activation of intracellular signalling proteins p38 and NF-κB p65, which were significantly increased by IL-17A, modestly increased by IL-17AF, and not increased by IL-17F. In combination with TNF-α, all three IL-17 cytokines induced IL6 and MMP3 mRNA expression to similar levels. Therefore, this study confirms that healthy and diseased tendon-derived fibroblasts are responsive to IL-17 cytokines and that IL-17A induces the most profound intracellular signalling activation and mRNA expression of inflammatory genes, followed by IL-17AF, and finally IL-17F. The ability of IL-17 cytokines to induce a direct response and activate diverse pro-inflammatory signalling pathways through synergy with other inflammatory mediators suggests a role for IL-17 family members as amplifiers of tendon inflammation and as potential therapeutic targets in tendinopathy

Interleukin-17A causes osteoarthritis-like transcriptional changes in human osteoarthritis-derived chondrocytes and synovial fibroblasts in vitro

Increased interleukin (IL)-17A has been identified in joints affected by osteoarthritis (OA), but it is unclear how IL-17A, and its family members IL-17AF and IL-17F, can contribute to human OA pathophysiology. Therefore, we aimed to evaluate the gene expression and signalling pathway activation effects of the different IL-17 family members in chondrocytes and synovial fibroblasts derived from cartilage and synovium of patients with end-stage knee OA. Immunohistochemistry staining confirmed that IL-17 receptor A (IL-17RA) and IL-17RC are expressed in end-stage OA-derived cartilage and synovium. Chondrocytes and synovial fibroblasts derived from end-stage OA patients were treated with IL-17A, IL-17AF, or IL-17F, and gene expression was assessed with bulk RNA-Seq. Hallmark pathway analysis showed that IL-17 cytokines regulated several OA pathophysiology-related pathways including immune-, angiogenesis-, and complement-pathways in both chondrocytes and synovial fibroblasts derived from end-stage OA patients. While overall IL-17A induced the strongest transcriptional response, followed by IL-17AF and IL-17F, not all genes followed this pattern. Disease-Gene Network analysis revealed that IL-17A-related changes in gene expression in these cells are associated with experimental arthritis, knee arthritis, and musculoskeletal disease gene-sets. Western blot analysis confirmed that IL-17A significantly activates p38 and p65 NF-κB. Incubation of chondrocytes and synovial fibroblasts with anti-IL-17A monoclonal antibody secukinumab significantly inhibited IL-17A-induced gene expression. In conclusion, the association of IL-17-induced transcriptional changes with arthritic gene-sets supports a role for IL-17A in OA pathophysiology. Future studies should further investigate the role of IL-17A in the OA joint to establish whether anti-IL-17 treatment could be a potential therapeutic option in OA patients with an inflammatory phenotype

The potential roles of high mobility group box 1 (HMGB1) in musculoskeletal disease: a systematic review

There is increasing evidence for the involvement of high mobility group box 1 (HMGB1) in inflammation, angiogenesis, and tumorigenesis. However, no studies have reviewed the role of HMGB1 in musculoskeletal disease. This systematic review aimed to evaluate the literature regarding the potential roles of HMGB1 in musculoskeletal disease (joint, tendon, ligament, intervertebral disc, bone). After searching PubMed, MEDLINE, and EMBASE databases up to 01‐01‐2020, 66 articles that measured HMGB1 expression in musculoskeletal disease were included. Immune and tissue resident stromal cells expressed HMGB1, and both diseased human tissues and animal disease models showed increased HMGB1 expression relative to controls. Administration of recombinant HMGB1 to diseased musculoskeletal tissues induced inflammation, whereas blocking HMGB1 ameliorated histopathological and clinical severity of disease. HMGB1 redox status was investigated in only 3% of the articles: fully reduced HMGB1 promoted chemotaxis of leukocytes and tissue repair, whereas disulphide HMGB1 acted as a pro‐inflammatory mediator. Our review highlights that while HMGB1 is an important mediator in musculoskeletal disease, its redox status remains understudied. Identification of HMGB1 redox status in musculoskeletal tissues is critical to advance understanding of the diverse biological functions of HMGB1 in musculoskeletal disease. Importantly, this will inform future therapeutic strategies to target HMGB1

Electrospun scaffold micro-architecture induces an activated transcriptional phenotype within tendon fibroblasts

Biomaterial augmentation of surgically repaired rotator cuff tendon tears aims to improve the high failure rates (∼40%) of traditional repairs. Biomaterials that can alter cellular phenotypes through the provision of microscale topographical cues are now under development. We aimed to systematically evaluate the effect of topographic architecture on the cellular phenotype of fibroblasts from healthy and diseased tendons. Electrospun polydioxanone scaffolds with fiber diameters ranging from 300 to 4000 nm, in either a highly aligned or random configuration, were produced. Healthy tendon fibroblasts cultured for 7 days on scaffolds with highly aligned fibers demonstrated a distinctive elongated morphology, whilst those cultured on randomly configured fibers demonstrated a flattened and spread morphology. The effect of scaffold micro-architecture on the transcriptome of both healthy and diseased tendon fibroblasts was assessed with bulk RNA-seq. Both healthy (n = 3) and diseased tendon cells (n = 3) demonstrated a similar transcriptional response to architectural variants. Gene set enrichment analysis revealed that large diameter (≥2000 nm) aligned scaffolds induced an upregulation of genes involved in cellular replication and a downregulation of genes defining inflammatory responses and cell adhesion. Similarly, PDPN and CD248, markers of inflammatory or “activated” fibroblasts, were downregulated during culture of both healthy and diseased fibroblasts on aligned scaffolds with large (≥2000 nm) fiber diameters. In conclusion scaffold architectures resembling that of disordered type III collagen, typically present during the earlier phases of wound healing, resulted in tendon fibroblast activation. Conversely, scaffolds mimicking aligned diameter collagen I fibrils, present during tissue remodelling, did not activate tendon derived fibroblasts. This has implications for the design of scaffolds used during rotator cuff repair augmentation

In vitro evaluation of the response of human tendon‐derived stromal cells to a novel electrospun suture for tendon repair

Recurrent tears after surgical tendon repair remain common. Repair failures can be partly attributed to the use of sutures not designed for the tendon cellular niche nor designed for the promotion of repair processes. Synthetic electrospun materials can mechanically support the tendon while providing topographical cues that regulate cell behavior. Here, a novel electrospun suture made from twisted polydioxanone (PDO) polymer filaments is compared to PDS II, a clinically used PDO suture currently utilized in tendon repair. We evaluated the ability of these sutures to support the attachment and proliferation of human tendon‐derived stromal cells using PrestoBlue and scanning electron microscopy. Suture surface chemistry was analyzed using x‐ray photoelectron spectroscopy. Bulk RNA‐Seq interrogated the transcriptional response of primary tendon‐derived stromal cells to sutures after 14 days. Electrospun suture showed increased initial cell attachment and a stronger transcriptional response compared with PDS II, with relative enrichment of pathways including mTorc1 signaling and depletion of epithelial‐to‐mesenchymal transition. Neither suture induced transcriptional upregulation of inflammatory pathways compared to baseline. Twisted electrospun sutures therefore show promise in improving outcomes in surgical tendon repair by allowing increased cell attachment while maintaining an appropriate tissue response