Fibulin1C peptide induces cell attachment and extracellular matrix deposition in lung fibroblasts

Abstract

Fibulin-1 is an extracellular matrix (ECM) protein, levels of which are elevated in serum and lung tissue from patients with idiopathic pulmonary fibrosis compared to healthy volunteers. Inhibition of fibulin-1C, one of four fibulin-1 isoforms, reduced proliferation and wound healing in human airway smooth muscle (ASM) cells. This study identified the bioactive region/s of fibulin-1C which promotes fibrosis. Seven fibulin-1C peptides were synthesized and used to pre-coat tissue culture plates before lung derived ASM cells and fibroblasts from patients with pulmonary fibrosis (PF), chronic obstructive pulmonary disease (COPD) or neither disease (Control) were plated. Peptide effects on in vitro measures of fibrosis: cell attachment, proliferation and viability, and ECM deposition, were examined. Among these peptides, peptide 1C1 (FBLN1C1) enhanced ASM cell and fibroblast attachment. FBLN1C1 increased mitochondrial activity and proliferation in fibroblasts. In addition, FBLN1C1 stimulated fibulin1 deposition in PF and COPD fibroblasts, and augmented fibronectin and perlecan deposition in all three groups. Peptides FBLN1C2 to FBLN1C7 had no activity. The active fibulin-1C peptide identified in this study describes a useful tool for future studies. Ongoing investigation of the role of fibulin-1 may reveal the mechanisms underlying the pathphysiology of chronic lung diseases.

Fibulin-1 regulates the pathogenesis of tissue remodeling in respiratory diseases

“…Several types of mesenchymal cells are capable of producing Fbln1, and in the airways and lungs, there is likely not a single cellular source. In previous studies, we showed that ASM cells (13) and fibroblasts (14, 17) produce Fbln1. We also showed that Fbln1 is not upregulated by TGF-β (17), but TGF-β–stimulated fibroblasts can incorporate exogenously produced Fbln1 into the ECM.…”

“…We also showed that Fbln1 is not upregulated by TGF-β (17), but TGF-β–stimulated fibroblasts can incorporate exogenously produced Fbln1 into the ECM. Furthermore, Fbln1c1 peptide promotes the production of new Fbln1c1 in fibroblasts (14). Taken together, our studies indicate that soluble Fbln1c may be produced by cells, such as epithelial cells, and is incorporated into the airway by fibroblasts, especially when levels of profibrotic stimuli are increased, as occurs in COPD.…”

“…This shows that CS affects Fbln1 homeostasis, increasing its production and likely modifying its degradation and peptide generation. Fbln1c peptides can stimulate Fbln1 deposition in COPD fibroblasts — potentially through a feed-forward mechanism — and promote the attachment of ASM cells and fibroblasts; they also augment Fn and perlecan deposition (14). Some proteases, such as MMP13, cleave Fbln1 (31, 32), and the mRNA expression of this enzyme is upregulated in CS-exposed mice (Supplemental Table 1).…”

“…Fbln1 is known to play important roles in wound repair (13, 14) and is associated with several respiratory diseases. Increased levels of Fbln1 occur in serum and bronchoalveolar lavage fluid (BALF) of asthma patients, and inhibition of Fbln1c expression by antisense oligonucleotide reduced the proliferation of ASM cells from these patients (13).…”

“…Increased levels of Fbln1 occur in serum and bronchoalveolar lavage fluid (BALF) of asthma patients, and inhibition of Fbln1c expression by antisense oligonucleotide reduced the proliferation of ASM cells from these patients (13). In IPF, ECM proteins are increased in both plasma and lung tissue (15), and Fbln1c variant–specific peptide increases the proliferation of lung fibroblasts, the main producers of ECM, in COPD and IPF patients (14). Cytokines associated with lung diseases, such as TGF-β, that are known to induce ECM proteins (16) also stimulate Fbln1 production in ASM cells from COPD patients, further indicating roles for Fbln1 in airway remodeling (17).…”