The Mechanical Environment Modulates Intracellular Calcium Oscillation Activities of Myofibroblasts

Myofibroblast contraction is fundamental in the excessive tissue remodeling that is characteristic of fibrotic tissue contractures. Tissue remodeling during development of fibrosis leads to gradually increasing stiffness of the extracellular matrix. We propose that this increased stiffness positively feeds back on the contractile activities of myofibroblasts. We have previously shown that cycles of contraction directly correlate with periodic intracellular calcium oscillations in cultured myofibroblasts. We analyze cytosolic calcium dynamics using fluorescent calcium indicators to evaluate the possible impact of mechanical stress on myofibroblast contractile activity. To modulate extracellular mechanics, we seeded primary rat subcutaneous myofibroblasts on silicone substrates and into collagen gels of different elastic modulus. We modulated cell stress by cell growth on differently adhesive culture substrates, by restricting cell spreading area on micro-printed adhesive islands, and depolymerizing actin with Cytochalasin D. In general, calcium oscillation frequencies in myofibroblasts increased with increasing mechanical challenge. These results provide new insight on how changing mechanical conditions for myofibroblasts are encoded in calcium oscillations and possibly explain how reparative cells adapt their contractile behavior to the stresses occurring in normal and pathological tissue repair.CG is supported by a post-doctoral fellowship from the Canadian Institutes of Health Research (CIHR) (grant 101130). The research of BH is supported by the CIHR (grants 210820 and 286720), the Collaborative Health Research Programme (CIHR/NSERC grants 1004005 and 413783), the Canada Foundation for Innovation and Ontario Research Fund (CFI/ORF grant 26653), and the Heart and Stroke Foundation Ontario (grant NA7086). Some of the data presented herein were funded from the European Union’s Seventh Framework Program (FP7/2007-2013) under grant agreement 237946. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript