Anne-Marie Koop

7 263 Figure 2 . Assessment of right ventricular remodelling induced by PAB upon cardiac depletion of Hand2. a) Fulton’s index values (ratio of right ventricular weight to left ventricular plus septal weight) of Hand2F/F and MCM-Hand2F/F animals either after sham or PAB surgery; b) High-magnification of representative images of histological sections stained for wheat germ agglutinin (WGA); c) Quantification of CSA in b, n=30 microscopic field/heart, 3 hearts. Quantitative real-time PCR analysis was performed to assess the expression levels of several genes known to be related to cardiac hypertrophy in RV tissue from Hand2F/F and MCM-Hand2F/F animals either after sham or PAB surgery: d) natriuretic peptides atrial natriuretic factor (Nppa); e) brain natriuretic peptide (Nppb); f) β -skeletal actin (Acta1); g) β -myosin heavy chain (Myh7); h) regulator of Calcineurin 1 Isoform 4 (Rcan1-4); i) High-magnification of representative images of histological sections stained for Sirius Red; j) Quantification of collagen deposition in i, n=30 microscopic field/heart, 3 hearts. Quantitative real- time PCR analysis of k) collagen type I alpha 1 chain (Col1A1); l) transforming growth factor beta (TGF- β ) and m) endoglin; n) Capillaries in RV sections of Hand2F/F and MCM-Hand2F/F animals subjected to either sham or PAB surgery were identified by isolectin B4 immunohistochemistry combined with WGA and, from the images obtained, we determined the ratio of capillaries per cardiomyocyte ratios; o) Quantitative real-time PCR analysis of vascular endothelial growth factor receptor 2 (Vegfr2) expression levels in the RV of Hand2F/F and MCM-Hand2F/F animals, subjected to either sham or PAB surgery. Data are from 5-10 animals per group; ∗ p < 0.05 between indicated groups (error bars are s.e.m.). Effects of cardiac silencing of Hand2 in the function and morphology of the LV under conditions of right ventricular pressure overload Based on interventricular interaction, any changes in RV shape will have consequences for the LV. While we observed increased eccentricity for the banded animals at both end-diastole and end-systole, no differences were observed between control and knockout mice ( figure 3a and 3b ). Increased LV eccentricity index reflects increased pressure of the RV and represents septal flattening which affects LV function and remodelling. Pressure overloaded animals, independent of the genotype, displayed decreased LV end-diastolic and -systolic volumes and subsequent decrease in stroke volumes and cardiac output ( table 3 ). No changes in systolic function were observed, as reflected by preserved LV ejection fraction throughout the different experimental groups ( table 3 ). Whereas animals subjected to PAB seem to display larger cardiomyocytes, this effect was not significant in the control or knockout mice ( figure 3c ). In agreement, a clear upregulation of the stress cardiac genes Nppa , Nppb and Myh7 in the LV of control-banded animals was observed but the expression levels remained at baseline in banded-knockout animals ( figure 3d-f ). A significant downregulation in Acta1 mRNA expression levels in the LV, after PAB, was observed independent of the genotype and in contrast to the RV ( figure 3g ). While a clear increase in Rcan1.4 was observed in the LV of