Modulation of cell fate by shock wave therapy in ischaemic heart disease.

AIMS: Cardiac shockwave therapy (SWT) improves left ventricular (LV) function in patients with ischaemic cardiomyopathy. Shockwave therapy activates Toll-like receptor 3 (TLR3), a receptor-inducing chromatin remodelling and nuclear reprogramming of cardiac cells. We hypothesized that mechanical activation of TLR3 facilitates reprogramming of fibroblasts towards endothelial cells restoring myocardial perfusion and function. METHODS AND RESULTS: Human cardiac fibroblasts were treated by mechanical stimulation via SWT or TLR3 agonist Poly(I:C) in the presence of endothelial induction medium. A lineage tracing experiment was performed in a transgenic mouse model of Fsp1-Cre/LacZ mice after coronary occlusion. Left ventricular function and scarring were assessed. Single-cell sequencing including RNA trajectory analysis was performed. Chromatin remodelling and epigenetic plasticity were evaluated via western blot and Assay for Transposase-Accessible Chromatin sequencing. Mechanical stimulation of human fibroblasts with SWT activated TLR3 signalling and enhanced the expression of endothelial genes in a TLR3-dependent fashion. The induced endothelial cells (ECs) resembled genuine ECs in that they produced endothelial nitric oxide and formed tube-like structures in Matrigel. In a lineage tracing experiment in Fsp1-Cre/LacZ mice, shockwave treatment increased LacZ/CD31-positive cells (indicating transdifferentiation) after coronary occlusion. Furthermore, SWT reduced myocardial scar size and improved LV function. Single-cell RNA-seq and RNA trajectory analyses revealed that SWT induced an endothelial fibroblast cluster and mechanical stimulation induced significant changes in chromatin organization, with chromatin being more accessible after both treatments in 1705 genomic regions. CONCLUSION: Shockwave therapy enhances DNA accessibility via TLR3 activation and facilitates the transdifferentiation of fibroblasts towards endothelial cells in ischaemic myocardium.