CCN1 expression by fibroblasts is required for bleomycin-induced skin fibrosis

Katherine Quesnel; Xu Shi-Wen; James Hutchenreuther; Yizhi Xiao; Shangxi Liu; Alexander Peidl; Deboki Naskar; Walter L Siqueira; David B O'Gorman; Boris Hinz; Richard J Stratton; Andrew Leask

doi:10.1016/j.mbplus.2019.100009

CCN1 expression by fibroblasts is required for bleomycin-induced skin fibrosis

Matrix Biol Plus. 2019 Jul 6:3:100009. doi: 10.1016/j.mbplus.2019.100009. eCollection 2019 Aug.

Authors

Affiliations

¹ Department of Dentistry, University of Western Ontario, London, ON, N6A 5C1, Canada.
² Centre for Rheumatology, University College London (Royal Free Campus), London, NW3 2PF, UK.
³ Department of Physiology and Pharmacology, University of Western Ontario, London, ON, N6A 5C1, Canada.
⁴ Laboratory of Tissue Repair and Regeneration, Faculty of Dentistry, University of Toronto, Toronto, ON, M5G 1G6, Canada.
⁵ Roth McFarlane Hand and Upper Limb Centre, Lawson Research Institute, London, ON, N6A 4V2, Canada.
⁶ Departments of Biochemistry and Surgery, University of Western Ontario, London, N6A 5C1, ON, N6A 5C1, Canada.

Abstract

The microenvironment contributes to the excessive connective tissue deposition that characterizes fibrosis. Members of the CCN family of matricellular proteins are secreted by fibroblasts into the fibrotic microenvironment; however, the role of endogenous CCN1 in skin fibrosis is unknown. Mice harboring a fibroblast-specific deletion for CCN1 were used to assess if CCN1 contributes to dermal homeostasis, wound healing, and skin fibrosis. Mice with a fibroblast-specific CCN1 deletion showed progressive skin thinning and reduced accumulation of type I collagen; however, the overall mechanical property of skin (Young's modulus) was not significantly reduced. Real time-polymerase chain reaction analysis revealed that CCN1-deficient skin displayed reduced expression of mRNAs encoding enzymes that promote collagen stability (including prolyl-4-hydroxylase and PLOD2), although expression of COL1A1 mRNA was unaltered. CCN1-deficent skin showed reduced hydroxyproline levels. Electron microscopy revealed that collagen fibers were disorganized in CCN1-deficient skin. CCN1-deficient mice were resistant to bleomycin-induced skin fibrosis, as visualized by reduced collagen accumulation and skin thickness suggesting that deposition/accumulation of collagen is impaired in the absence of CCN1. Conversely, CCN1-deficient mice showed unaltered wound closure kinetics, suggesting de novo collagen production in response to injury did not require CCN1. In response to either wounding or bleomycin, induction of α-smooth muscle actin-positive myofibroblasts was unaffected by loss of CCN1. CCN1 protein was overexpressed by dermal fibroblasts isolated from lesional (i.e., fibrotic) areas of patients with early onset diffuse scleroderma. Thus, CCN1 expression by fibroblasts, being essential for skin fibrosis, is a viable anti-fibrotic target.

Keywords: CCN family; CCN1; Connective tissue; Dermis; Fibrosis; Matricellular proteins; Scleroderma; cyr61.