Left ventricular hypertrophy and metabolic resetting in the Notch3-deficient adult mouse heart
The heart depends on a functional vasculature for oxygenation and transport of nutrients, and while occlusion of the coronary arteries can lead to myocardial infarction, it remains less explored how a more subtle primary impairment of the vasculature can indirectly affect cardiac function and morphology of the heart. Notch3-deficiency causes vascular smooth muscle cell (VSMC) loss in the vasculature but the consequences for the heart remain largely elusive. Here, we demonstrate that Notch3-/- mice have enlarged hearts with left ventricular hypertrophy and mild fibrosis. Cardiomyocytes were hypertrophic but not hyperproliferative, and the expression of several cardiomyocyte markers, including TnT2, MYH6, MYH7 and Actn2, was altered. Furthermore, expression of genes regulating the metabolic status of the heart was altered: both Pdk4 and Cd36 were downregulated, indicating a metabolic switch from fatty acid oxidation to glucose consumption. Notch3-/- mice furthermore showed lower liver lipid content. Notch3 was expressed in heart VSMC and pericytes but not in cardiomyocytes, suggesting that a perturbation of Notch signalling in VSMC and pericytes indirectly impairs the cardiomyocytes. In keeping with this, Pdgfbret/ret mice, characterized by reduced numbers of VSMC and pericytes, showed left ventricular and cardiomyocyte hypertrophy. In conclusion, we demonstrate that reduced NOTCH3 or PDGFB signalling in vascular mural cells lead to cardiomyocyte dysfunction. Overall design: Mice were euthanized, the organs removed and immediately fresh frozen. RNA from heart tissue of c57bl/6j Notch3 +/+ (N3 WT)  and Notch3 -/- (N3 KO) was prepared and sequenced as described. Clustering was done by 'cBot' and samples were sequenced on HiSeq3000(HiSeq Control Software 2.2.58/RTA 1.18.64) with a 1x51 setup using 'HiSeq SBS Kit v4' chemistry. The Bcl to FastQ conversion was performed applying standard parameters of the Illumina pipeline (bcl2fastq) using Nextera index adapters. The quality scale used is Sanger / phred33 / Illumina 1.8+.