GSE167892
Nuclear mechanosensing drives chromatin remodeling of persistently activated myofibroblasts
Fibrotic disease is caused by persistently activated fibroblasts, known as myofibroblasts, that continuously deposit extracellular matrix and fail to de-activate after injury resolution. There are currently no treatments for fibrotic disease; our study addresses the mechanisms whereby myofibroblasts persist in fibrotic tissues such as diseased cardiac valves. We exploit photo-softening hydrogels as synthetic valve tissue mimics and valve fibroblasts as a model to study how stiffness controls pathological myofibroblast activation and their persistence. We show that persistent myofibroblasts have condensed chromatin structure with genome-wide alterations and that this is associated with stabilization of the actin cytoskeleton. Disconnecting the nucleus from the cytoskeleton prevents chromatin condensation and myofibroblast persistence. Notably, myofibroblasts in patients with aortic valve stenosis display a condensed chromatin structure compared to myofibroblasts in a healthy patient, similar to the difference observed between cultured persistent myofibroblasts and transient myofibroblasts. Collectively, our results reveal that nuclear mechanosensing leads to distinct chromatin signatures in persistent myofibroblasts and that this novel cellular mechanism is likely relevant to human fibrotic disease. Overall design: Primary porcine aortic valvular interstitial cells were isolated and seeded onto PEGdiPDA hydrogels (G' = 4 kPa (stiff) or 2 kPa (soft)). The cells were cultured in Media 199 (Life Technologies) supplemented with 1% human serum, 50 U/mL penicillin, 50 µg/mL streptomycin, and 1 µg/mL amphotericin B for 3 days or 9 days.