Crohn’s Disease Fibroblasts Overproduce the Novel Protein KIAA1199 to Create Proinflammatory Hyaluronan Fragments

Abstract

Background & Aims Crohn’s Disease (CD) is a chronic inflammatory disease of the gastrointestinal tract. Fibrosis, a serious complication of CD, occurs when activated intestinal fibroblasts deposit excessive amounts of extracellular matrix (ECM) in affected areas. A major component of the ECM is high molecular weight hyaluronan (HA) which, when depolymerized to low molecular weight fragments, becomes pro-inflammatory and pro-fibrotic. Mechanisms for HA degradation are incompletely understood, but the novel protein KIAA1199 was recently discovered to degrade HA. We hypothesize that KIAA1199 protein is increased in CD colon fibroblasts and generates HA fragments that foster inflammation and fibrosis. Methods Fibroblasts were isolated from explants of surgically resected colon tissue from CD and non-IBD control (ND) patients. Protein levels and tissue distribution of KIAA1199 were assessed by immunoblot and immunostaining, and functional HA degradation was measured biochemically. Results Elevated levels of KIAA1199 protein were produced and deposited in the ECM by cultured CD fibroblasts compared to controls. Treatment of fibroblasts with the pro- inflammatory cytokine interleukin-6 (IL-6) increased deposition of KIAA1199 in the ECM. CD fibroblasts also produce significantly higher levels of IL-6 compared to controls, and antibody blockade of IL-6 receptors in CD colon fibroblasts decreased the level of KIAA1199 protein in the ECM. Colon fibroblasts degrade HA, however siRNA silencing of KIAA1199 abrogated that ability. Conclusions CD fibroblasts produce elevated levels of KIAA1199 primarily through an IL-6 driven autocrine mechanism. This leads to excessive degradation of HA and the generation of pro-inflammatory HA fragments that contributes to maintenance of gut inflammation and fibrosis.

Transcriptome profiling reveals the complexity of pirfenidone effects in idiopathic pulmonary fibrosis

“…CEMIP influences the extracellular environment by participating in the catabolism of HA [28], which not only alters the strength, lubrication and hydration of ECM but also regulates adhesion, migration, proliferation and differentiation of a variety of cells [29]. We found a marked increase in CEMIP mRNA and protein expression in LH and FB of IPF patients as compared to donors.…”

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“…The composition and stiffness of the ECM are also likely to be involved. Fibroblasts from patients with CD produce increased levels of cell migration-inducing hyaluronan-binding protein through an autocrine pathway regulated by IL6 51 . Hyaluronan degradation generates damage-associated molecular pattern fragments, which sustain inflammation and fibrosis to contribute to the cycle of inflammation and fibrosis.…”

The extracellular matrix in IBD

“…Recently, ECM remodeling, through expression of an unsuspected ECM cleaving enzyme, KIAA1199, that degrades the glycosaminoglycan hyaluronan was also associated with Crohn’s disease [3]. Degradation products of the HA matrix are considered damage associated molecular pattern (DAMP) molecules that are recognized by TLR receptors and initiate immune responses [4–6] including sterile inflammation [7].…”

“…Additionally, HA fragments also promote wound healing through enhanced fibroblast proliferation and myoblast differentiation which may contribute to fibrotic processes in IBD [28]. Elevated HA fragment deposition in the intestines is associated with inflamed IBD tissue [3], and may further perpetuate innate immune responses in IBD.…”