Differential β₃Integrin Expression Regulates the Response of Human Lung and Cardiac Fibroblasts to Extracellular Matrix and Its Components

Abstract

Extracellular matrix (ECM) derived from whole organ decellularization has been successfully used in a variety of tissue engineering applications. ECM contains a complex mixture of functional and structural molecules that are ideally suited for the tissue from which the ECM is harvested. However, decellularization disrupts the structural properties and protein composition of the ECM, which may impact function when cells such as the fibroblast are reintroduced during recellularization. We hypothesized that the ECM structure and composition, fibroblast source, and integrin expression would influence the fibroblast phenotype. Human cardiac fibroblasts (HCFs) and normal human lung fibroblasts (NHLFs) were cultured on intact cardiac ECM, collagen gels, and coatings composed of cardiac ECM, lung ECM, and individual ECM components (collagen and fibronectin [FN]) for 48 h. COL1A expression of HCFs and NHLFs cultured on ECM and FN coatings decreased to <50% of that of untreated cells; COL1A expression for HCFs cultured on ECM coatings was one-to twofold higher than HCFs cultured on intact ECM. NHLFs cultured on ECM and FN coatings expressed 12-to 31-fold more alpha-smooth muscle actin (aSMA) than HCFs; the aSMA expression for HCFs and NHLFs cultured on ECM coatings was *2-to 5-fold higher than HCFs and NHLFs cultured on intact ECM. HCFs expressed significantly higher levels of b 3 and b 4 integrins when compared to NHLFs. Inhibition of the b 3 integrin, but not b 4 , resulted in a 16-to 26-fold increase in aSMA expression in HCFs cultured on ECM coatings and FN. Our results demonstrate that b 3 integrin expression depends on the source of the fibroblast and that its expression inhibits aSMA expression (and thus the myofibroblast phenotype). We conclude that the fibroblast source and integrin expression play important roles in regulating the fibroblast phenotype.

Decellularized Extracellular Matrix Materials for Cardiac Repair and Regeneration

“…While both dECM powders induced neovascularization in the infarct area and cell infiltration into the materials in vivo, the liver powder was more effective, although there was limited direct comparisons on dECM composition and function. Merna et al grew heart and lung fibroblasts on cECM and lung ECM (lECM) and found that fibroblast source and integrin expression were more important than dECM source in myofibroblast differentiation potential . They also characterized the differences in dECM composition, where lECM expressed collagen II and IX exclusively and cECM expressed collagen VII, fibrinogen, and heparan sulfate proteoglycan.…”

“…While these studies have attempted to compare differences in tissue and species sourcing between cECM and other dECM through quantification of chemical composition or assessments in cellular responses, comparison between implementing differently sourced dECM in the treatment of cardiovascular diseases is critical in determining which sourcing allows for the most effective therapy . The studies discussed in this section point toward diverse differences between dECM sources based on tissue or species source.…”

“…In vitro systems using cardiac specific cells or stem cells on cardiac specific dECM have also been used to determine the biology of cell–ECM binding in the heart. Merna et al grew human cardiac and lung fibroblasts on intact cECM, collagen gels, and coatings of cECM, lECM, and ECM components . Cardiac fibroblasts had higher expression of β3 and β4 integrins compared to lung fibroblasts, and inhibition of only β3 integrin resulted in substantial increases to myofibroblast differentiation of cardiac fibroblasts cultured on either lECM, cECM, or fibronectin.…”

Tissue engineering the cardiac microenvironment: Multicellular microphysiological systems for drug screening

“…Cardiac fibroblasts also produce periostin, which is highly expressed in the developing heart, and has been shown to induce cardiomyocyte proliferation in vitro and in vivo [116]. Fibronectin, fibrillin, elastin, proteoglycans, and glycoproteins are also present in the cardiac ECM, deposited mainly by cardiac fibroblasts [117,118]. Fibroblasts also secrete matrix metalloproteinases (MMPs) in order to remodel the cardiac ECM.…”

“…One of the challenges in using fibroblast co-culture models is the heterogeneity of fibroblasts within the body, showing significant variation in function even within a single organ system [118,122,132]. Most researchers have used fibroblast sources that are not of cardiac origin, which may be a concern for recapitulating the physiological microenvironment of the heart.…”