Regulation of Cellular Senescence Is Independent from Profibrotic Fibroblast-Deposited ECM.

Kaj E C Blokland,Darryl A Knight,Barbro N Melgert,Greta J Teitsma,Theo Borghuis,Habibie Habibie,Michael Schuliga,Simon D Pouwels,Janette K Burgess,Corry-Anke Brandsma

doi:10.3390/cells10071628

Abstract

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disease with poor survival. Age is a major risk factor, and both alveolar epithelial cells and lung fibroblasts in this disease exhibit features of cellular senescence, a hallmark of ageing. Accumulation of fibrotic extracellular matrix (ECM) is a core feature of IPF and is likely to affect cell function. We hypothesize that aberrant ECM deposition augments fibroblast senescence, creating a perpetuating cycle favouring disease progression. In this study, primary lung fibroblasts were cultured on control and IPF-derived ECM from fibroblasts pretreated with or without profibrotic and prosenescent stimuli, and markers of senescence, fibrosis-associated gene expression and secretion of cytokines were measured. Untreated ECM derived from control or IPF fibroblasts had no effect on the main marker of senescence p16Ink4a and p21Waf1/Cip1. However, the expression of alpha smooth muscle actin (ACTA2) and proteoglycan decorin (DCN) increased in response to IPF-derived ECM. Production of the proinflammatory cytokines C-X-C Motif Chemokine Ligand 8 (CXCL8) by lung fibroblasts was upregulated in response to senescent and profibrotic-derived ECM. Finally, the profibrotic cytokines transforming growth factor β1 (TGF-β1) and connective tissue growth factor (CTGF) were upregulated in response to both senescent- and profibrotic-derived ECM. In summary, ECM deposited by IPF fibroblasts does not induce cellular senescence, while there is upregulation of proinflammatory and profibrotic cytokines and differentiation into a myofibroblast phenotype in response to senescent- and profibrotic-derived ECM, which may contribute to progression of fibrosis in IPF.

Highlights

To investigate the effect of deposited extracellular matrix (ECM) by control or Idiopathic pulmonary fibrosis (IPF) lung fibroblasts on the senescence induction, we first wanted to confirm that our decellularization protocol resulted in cell-free matrix deposition
Fibroblast treated with transforming growth factor β1 (TGF-β1) show increased total ECM deposition and structure, of which IPF-derived demonstrates the most change
When fibroblasts were cultured on ECM derived from TGF-β1or H2 O2 -stimulated Ctrl- or IPF-fibroblasts, we detected upregulation in CXCL8, connective tissue growth factor (CTGF) and Collectively, the data presented in this study suggest that exposure of fibroblasts to Ctrl- or IPF-derived ECM under basal conditions does not induce cellular senescence nor induce cytokine production

Summary

Introduction

Changes in the ECM of the lung during ageing, such as loss of elastin and increased collagen contributes to aberrant composition that negatively influences proliferation, migration and differentiation of cells [2]. Mesenchymal cells, such as residing fibroblasts, are responsible for maintaining and remodelling the ECM during homeostasis. While senescence is an important regulatory element during wound repair, dysregulation and accumulation of senescent cells during ageing contributes to an aberrant repair response that leads to fibrosis [6,10]. The negative impact of senescence is mainly attributed to SASP and the inability to clear senescent cells favouring disease progression

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