Tenascin-C-mediated suppression of extracellular matrix adhesion force promotes entheseal new bone formation through activation of Hippo signalling in ankylosing spondylitis

Abstract

ObjectivesThe aim of this study was to identify the role of tenascin-C (TNC) in entheseal new bone formation and to explore the underlying molecular mechanism.MethodsLigament tissue samples were obtained from patients with ankylosing spondylitis (AS) during surgery. Collagen antibody-induced arthritis and DBA/1 models were established to observe entheseal new bone formation. TNC expression was determined by immunohistochemistry staining. Systemic inhibition or genetic ablation of TNC was performed in animal models. Mechanical properties of extracellular matrix (ECM) were measured by atomic force microscopy. Downstream pathway of TNC was analysed by RNA sequencing and confirmed with pharmacological modulation both in vitro and in vivo. Cellular source of TNC was analysed by single-cell RNA sequencing (scRNA-seq) and confirmed by immunofluorescence staining.ResultsTNC was aberrantly upregulated in ligament and entheseal tissues from patients with AS and animal models. TNC inhibition significantly suppressed entheseal new bone formation. Functional assays revealed that TNC promoted new bone formation by enhancing chondrogenic differentiation during endochondral ossification. Mechanistically, TNC suppressed the adhesion force of ECM, resulting in the activation of downstream Hippo/yes-associated protein signalling, which in turn increased the expression of chondrogenic genes. scRNA-seq and immunofluorescence staining further revealed that TNC was majorly secreted by fibroblast-specific protein-1 (FSP1)+fibroblasts in the entheseal inflammatory microenvironment.ConclusionInflammation-induced aberrant expression of TNC by FSP1+fibroblasts promotes entheseal new bone formation by suppressing ECM adhesion forces and activating Hippo signalling.

CXCL12/CXCR4-Rac1–mediated migration of osteogenic precursor cells contributes to pathological new bone formation in ankylosing spondylitis

“…The SMTS mice model were constructed in wild-type (C57BL/6J), CXCR4 fl/fl ;Prx1-creERT (C57BL/6J), and CXCL12 hi/hi ;Col2a1-creERT (C57BL/6J) mice. The procedure of SMTS surgery is as described in previous studies ( 15 ). Briefly, 8-weeks-old male mice were anesthetized by ketamine and xylazine.…”

“…Elucidation of pathogenetic factors is important for identifying targets for intervention. Our and others' previous studies have found a variety of important factors in the entheseal microenvironment related to pathological new bone formation, including inflammation, growth factor signaling cascades, and abnormal mechanical transduction (5,(13)(14)(15). In this bone-forming microenvironment, osteogenic precursor cells (OPCs) are considered responsive cells that commit ossification.…”

Inflammation, new bone formation and aorta

“…Furthermore, in a latest milestone study, a secreted extracellular matrix protein, tenascin‐C (TNC), is proven to be aberrantly induced by TNF‐α, IL‐17A and IL‐22 in ligament and entheseal tissues in AS patients. The inhibition of TNC could significantly suppress new bone formation both in vitro and in vivo 28,29 . Interestingly, TNC also actively participates in atherosclerotic plaque/aneurysm formation, 30 which suggests that TNC might be a key molecule to align aorta‐vertebrae remodeling.…”

Tenascin-C, a novel target to inhibit new bone formation in axial spondyloarthritis, linked with inflammation, mechanical strain and tissue damage

“…In this journal, Li et al identify tenascin-C (TNC) as a key driver of new bone formation originating from the enthesis, and mechanistic experiments intriguingly position this extracellular matrix molecule as a converging node between inflammation, mechanical strain, tissue damage and new bone formation. 6 TNC is a glycoprotein with a number of remarkable features as extensively discussed by Midwood et al 7 The founding father of the tenascin family, TNC is abundantly found in extra-cellular matrix during development. The molecule's name is based on its abundance in tendons (ten-) from embryos or nasci, Latin for 'to be born'.…”

“…In a whole transcriptome analysis approach using an amazing collection of spinal ligament tissues from axial spondyloarthritis patients and from controls with primarily orthopaedic issues, TNC and genes associated with increased levels of TNC were found to be upregulated in diseased tissue compared with the controls. 6 Subsequently, the authors demonstrate how absence of the Tnc gene in genetically modified mice as well as anti-TNC antibody treatment inhibit the development of joint ankylosis in dedicated animal models of arthritis. They further unravel the underlying molecular mechanism by extensive in vitro and in vivo work: presence of TNC decreases the adhesion force of the extracellular matrix.…”