Calcium Signaling Regulates Valvular Interstitial Cell Alignment and Myofibroblast Activation in Fast-Relaxing Boronate Hydrogels.

Abstract

The role viscoelasticity in fibrotic disease progression is an emerging area of interest. Here, a fast-relaxing hydrogel system is exploited to investigate potential crosstalk between calcium signaling and mechanotransduction. Poly(ethylene glycol) (PEG) hydrogels containing boronate and triazole crosslinkers are synthesized, with varying ratios of boronate to triazole crosslinks to systematically vary the extent of stress relaxation. Valvular interstitial cells (VICs) encapsulated in hydrogels with the highest levels of stress relaxation (90%) exhibit a spread morphology by day 1 and are highly aligned (80 ± 2%) by day 5. Key myofibroblast markers, including α-smooth muscle actin (αSMA) and collagen 1a1 (COL1A1), are significantly elevated. VIC myofibroblast activation decreases by 42 ± 18% through inhibition of mechanotransduction, independently of VIC morphology and alignment. Calcium signaling through a transient receptor potential vanilloid 4 (TRPV4) is found to regulate VIC spreading, alignment, and activation in a time dependent manner. Inhibition of calcium signaling at early time points results in disturbed cell alignment, decreased mechanotransduction, and diminished activation, while inhibition at later time points only causes partially reduced myofibroblast activation. These results suggest a potential crosstalk mechanism, where calcium signaling acts upstream of mechanosensing and can regulate VIC myofibroblast activation independently of mechanotransduction.