Stiff substrates inhibit collagen accumulation via integrin?2(i1, FAK and Src kinases in human atrial fibroblast and myofibroblast cultures derived from patients with aortal stenosis

The aim of the study was to confirm whether cell substrate stiffness may participate in the regulation of fibrosis. The involvement of integrin alpha 2(i1, focal adhesion kinase (FAK) and Src kinase in signal transmission was investigated. Human atrial fibroblasts and myofibroblasts were cultured in both soft (2.23 +/- 0.8 kPa) and stiff (8.28 +/- 1.06 kPa) polyacrylamide gels. The cells were derived from the right atrium of patients with aortal stenosis undergoing surgery. The isolated cells, identified as fibroblasts or myofibroblasts, were stained positively with alpha smooth muscle actin, vimentin and desmin. The cultures settled on stiff gel demonstrated lower intracellular collagen and collagen type I telopeptide (PICP) levels; however, no changes in alpha 1 chain of procollagen type I and III expression were noted. Inhibition of alpha 2(i1 integrin by TC-I 15 (10- 7 and 10-8 M) or alpha 2 integrin subunit silencing augmented intracellular collagen level. Moreover, FAK or Src kinase inhibitors increased collagen content within the culture. Lower TIMP4 secretion was reported within the stiff gel cultures but neither MMP 2 nor TIMP-1, 2 or 3 release was altered. The stiff substrate cultures also demonstrated lower interleukin-6 release. Substrate stiffness modified collagen deposition within the atrial fibroblast and myofibroblast cultures. The elasticity of the cellular environment exerts a regulatory influence on both synthesis and breakdown of collagen. Integrin alpha 2(i1, FAK and Src kinase activity participates in signal transmission, which may influence fibrosis in the atria of the human heart.

Automated summary

The aim of this study was to investigate whether cell substrate stiffness participates in the regulation of fibrosis. Human atrial fibroblasts and myofibroblasts were cultured on soft and stiff polyacrylamide gels to examine the effects on collagen deposition and synthesis. Integrin alpha 2(i1), focal adhesion kinase (FAK), and Src kinase were found to be involved in signal transmission, which influences fibrosis in the atria of the human heart.