Defective granulation tissue formation in mice with specific ablation of integrin-linked kinase in fibroblasts – role of TGFβ1 levels and RhoA activity

Abstract

SummaryWound healing crucially relies on the mechanical activity of fibroblasts responding to TGFb1 and to forces transmitted across focal adhesions. Integrin-linked kinase (ILK) is a central adapter recruited to integrin b1 tails in focal adhesions mediating the communication between cells and extracellular matrix. Here, we show that fibroblast-restricted inactivation of ILK in mice leads to impaired healing due to a severe reduction in the number of myofibroblasts, whereas inflammatory infiltrate and vascularization of the granulation tissue are unaffected. Primary ILK-deficient fibroblasts exhibit severely reduced levels of extracellular TGFb1, a-smooth muscle actin (aSMA) production and myofibroblast conversion, which are rescued by exogenous TGFb1. They are further characterized by elevated RhoA and low Rac1 activities, resulting in abnormal shape and reduced directional migration. Interference with RhoA-ROCK signaling largely restores morphology, migration and TGFb1 levels. We conclude that, in fibroblasts, ILK is crucial for limiting RhoA activity, thus promoting TGFb1 production, which is essential for dermal repair following injury.

COMP-assisted collagen secretion - a novel intracellular function required for fibrosis

“…To determine the in vivo relevance of COMP for collagen secretion, COMP-null and control mice were subjected to repeated intradermal injections of bleomycin (Yamamoto et al, 1999) or to excisional wounding (Blumbach et al, 2010;Gurtner et al, 2008;Schulz et al, 2015;Zweers et al, 2007).…”

“…Wounds were created and harvested according to standard protocols (Blumbach et al, 2010;Schulz et al, 2015;Zweers et al, 2007). In brief, female mice at the age of 10 weeks were anesthetized by intraperitoneal injection of ketamine (10 g/l) and xylazine (8 g/l) solution (10 µl/g body weight) (Park Davis, Karlsruhe, Germany and Erlangen, Germany, respectively).…”

Loss of Cardiomyocyte Integrin-Linked Kinase Produces an Arrhythmogenic Cardiomyopathy in Mice

“…ILK is important for fibroblast function, and fibroblast selective ILK deletion prevents myofibroblast differentiation. 24 Our studies, therefore, apply specifically to the result of ILK deficiency in cardiomyocytes. Complete loss of ILK function in all cell types might produce a different phenotype, particularly with respect to fibrotic changes.…”

Integrins in Wound Healing

“…132,133 Indeed, defective granulation tissue formation is seen in mice with fibroblast-specific ILK ablation. 134 Inhibition of a 9 b 1 integrin by a specific antibody also inhibits granulation tissue formation during skin wound healing. 59 Fibroblasts interact with fibrillar collagens via a 1 b 1 , a 2 b 1 , and a 11 b 1 integrins ( Table 2).…”