β3 Integrin in Cardiac Fibroblast Is Critical for Extracellular Matrix Accumulation during Pressure Overload Hypertrophy in Mouse

Abstract

The adhesion receptor β3 integrin regulates diverse cellular functions in various tissues. As β3 integrin has been implicated in extracellular matrix (ECM) remodeling, we sought to explore the role of β3 integrin in cardiac fibrosis by using wild type (WT) and β3 integrin null (β3−/−) mice for in vivo pressure overload (PO) and in vitro primary cardiac fibroblast phenotypic studies. Compared to WT mice, β3−/− mice upon pressure overload hypertrophy for 4 wk by transverse aortic constriction (TAC) showed a substantially reduced accumulation of interstitial fibronectin and collagen. Moreover, pressure overloaded LV from β3−/− mice exhibited reduced levels of both fibroblast proliferation and fibroblast-specific protein-1 (FSP1) expression in early time points of PO. To test if the observed impairment of ECM accumulation in β3−/− mice was due to compromised cardiac fibroblast function, we analyzed primary cardiac fibroblasts from WT and β3−/− mice for adhesion to ECM proteins, cell spreading, proliferation, and migration in response to platelet derived growth factor-BB (PDGF, a growth factor known to promote fibrosis) stimulation. Our results showed that β3−/− cardiac fibroblasts exhibited a significant reduction in cell-matrix adhesion, cell spreading, proliferation and migration. In addition, the activation of PDGF receptor associated tyrosine kinase and non-receptor tyrosine kinase Pyk2, upon PDGF stimulation were impaired in β3−/− cells. Adenoviral expression of a dominant negative form of Pyk2 (Y402F) resulted in reduced accumulation of fibronectin. These results indicate that β3 integrin-mediated Pyk2 signaling in cardiac fibroblasts plays a critical role in PO-induced cardiac fibrosis.

Mechanobiology of myofibroblast adhesion in fibrotic cardiac disease

“…In accordance with this, AVICs cultured on RGD-coated substrates express increased levels of MyoFB markers and of αvβ3 integrins and are more prone to calcification (Benton et al, 2009;Gu and Masters, 2010). Furthermore, β3 integrin expression in the heart is significantly increased after myocardial infarction, and expression of β3 integrins in CFs is necessary for the accumulation of collagen and fibronectin in response to pressure overload (Balasubramanian et al, 2012;Luo et al, 2014). This effect is likely to be mediated by the FA component talin, which links integrins to the cytoskeleton and is required for αvβ3-integrin-mediated mechanotransduction (RocaCusachs et al, 2009).…”

“…Another β1-containing integrin that protects cardiac cells against fibrosis is α2β1 integrin, the primary receptor for collagen-1, which (Balasubramanian et al, 2012;Luo et al, 2014) a Each valve leaflet is composed of three layers of tissue, atrialis, fibrosa and spongiosa.…”

Reversal of maladaptive fibrosis and compromised ventricular function in the pressure overloaded heart by a caveolin-1 surrogate peptide

“…Experiments were performed as previously described 39 with minor modifications. Soluble and insoluble fractions of left ventricle (LV) were prepared.…”

The Stressful Life of Cardiac Myofibroblasts

“…Similarly, the expression of integrin αvβ5 is upregulated in rat cardiac fibroblasts after treatment with TGF-β1 and angiotensin II [165]. Others have reported a critical role of β3 integrin for collagen I and fibronectin accumulation in conditions of pressure overload, using β3 integrin knock-out mice [166]. Pathological myofibroblast activation in diabetic cardiomyopathy is associated with highly upregulated levels of the collagen receptor α11β1 integrin and pathologically glycated collagen in conditions of diabetic cardiomyopathy enhances both α11 integrin and α-SMA expression [167].…”