Myofibroblast Derived Transglutaminase 2 Activity is Upregulated in Stricturing Crohn's Disease and its Inhibition Exerts Anti-Fibrotic Properties.

BACKGROUND & AIMS: Excessive accumulation of extracellular matrix (ECM) derived from human intestinal myofibroblasts (HIMF) drives the significant clinical problem of intestinal fibrosis. Fibrosis is believed to progress even in the absence of intestinal inflammation. ECM-bound transglutaminase 2 (TG2) enzyme may exert direct pro-fibrotic effects. We investigated the role of TG2 in intestinal fibrosis.

METHODS

TG2 expression and activity in human intestinal tissue and HIMF from strictured Crohn's disease (CDs), and controls were measured. ECM accumulation by HIMF in presence or absence of TG2 inhibitors was determined. Putative TG2 signaling pathways discovered in HIMF using bulk RNA sequencing (bulk-RNAseq) and single cell RNA sequencing (scRNAseq) were functionally validated. Role of TG2 in vivo was confirmed using inducible global knockout of TGM2 (encoding TG2) in two experimental fibrosis models.

RESULTS

TG activity was increased in CDs compared to controls, with up to 100% activity attributable to TG2. TG activity correlated with the degree of histopathologic tissue fibrosis. HIMF were the major source of TG2, with ≥95% of HIMF TG activity being derived from TG2. Tissue distribution of TG2 in myofibroblasts was confirmed by scRNAseq analysis. Selective inhibition of TG2 activity reduced fibronectin (FN), collagen (COL)I, III and VI accumulation by HIMF. Novel TG2 signaling pathways revealed by bulk-RNAseq, were functionally validated. Inducible TGM2 knockout prevented experimental fibrosis without affecting the degree of intestinal inflammation.

CONCLUSIONS

TG2 may be involved in inflammation-independent progression of intestinal fibrosis.