Angiogenesis and activated fibroblast in a model of premature ventricular contraction-induced cardiomyopathy.

Abstract

Premature ventricular contractions (PVCs) are the most common ventricular arrhythmia in the elderly, and when frequent, can result in PVC-induced cardiomyopathy (PVC-CM). PVC-CM canine model showed eccentric hypertrophy and fibrosis in the left ventricle (LV). The underlying structural and molecular mechanism behind this LV remodeling is unknown. In situ structural adaptations of the LV tissue and the activation of the VEGF/ERK1/2 signaling pathway were studied in the PVC-CM model. Pacemakers were implanted in healthy canines where PVCs were enabled only in the PVC-CM group (50% of PVC burden, 200-220-ms coupling interval) for 12 weeks. Fixed LV longitudinal- and cross-sections were stained with anti-α-SMA antibody, a marker of activated fibroblast (myofibroblasts) and smooth muscle cells (blood vessels), and WGA-AF633 (a marker of cell membranes). Confocal images were analyzed using artificial intelligence (AI)-powered autonomous software, AIVIA. Western blot (WB) analysis was used to study the pro-angiogenic signaling pathway and proteins associated with fibroblast activation. In situ analysis showed a significant increase in the total area and number of blood vessels, along with an increase in activated fibroblasts in PVC-CM LV sections. Also, the PVC group showed a 30% increase in the number of activated fibroblasts per cardiomyocyte compared with the sham group. The endothelial marker, eNOS, and IL-1β, a cytokine involved in fibroblast activation, were elevated in the PVC-CM group. Additionally, the VEGF-A, VEGF-B, and VEGF receptor 2 were upregulated in PVC-CM vs Sham; downstream ERK1/2 was hyperphosphorylated and overexpressed, and MMP9 (marker of fibroblast activation linked to this pathway) was elevated in PVC-CM vs Sham. In conclusion, activated fibroblasts and angiogenesis are a feature of the cardiac LV hypertrophic remodeling in PVC-CM.