Anne-Marie Koop

6 239 was determined from histological sections stained for isolectin B4 immunohistochemistry and WGA (bars, 20 μm), density of WT-sham animals was set at 1, 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 directly or indirectly related to cardiac hypertrophy in LV tissue from wildtype (WT) and MHC-miR-199b Tg (MHC-199b) animals, either after sham or PAB surgery: h) natriuretic peptides atrial natriuretic factor (Nppa); i) brain natriuretic peptide (Nppb); j) β -myosin heavy chain (Myh7); k) regulator of Calcineurin 1 Isoform 4 (Rcan1-4); l) nuclear NFAT kinase dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1a (Dyrk1a); m) transforming growth factor beta (TGF- β ) and n) vascular endothelial growth factor receptor 2 (Vegfr2). All PCR data are from 5-8 animals per group. Statistical analysis using One-way ANOVA with Tukeys multiple comparisons test. ∗ p<0.05 versus corresponding control group; #p<0.05 versus corresponding experimental group (error bars are s.e.m.). Following the molecular and cellular changes, we also assessed how RV stress, together with increased miR-199b expression levels, influenced LV function. LV eccentricity index, defined as the ratio of the length of two perpendicular minor- axis diameters, one of which bisected and was perpendicular to the interventricular septum, was obtained at end-systole and end-diastole ( figure 5a,b ). While we could detect an abnormal motion of the interventricular septum which is in accordance with RV remodelling, this effect was not different betweenWT and TG animals ( figure 5a,b ). Both end-diastolic and systolic volumes decreased in the TG animals subjected to PAB but remained unchanged in WT ( figure 5c,d ). A similar pattern was observed for left ventricular stroke volume (LVSV) ( figure 5e ), suggesting affected function. However, this was not reflected in the LV EF, for which no differences were observed between the different groups ( figure 5f ). Altogether, this data confirms that the LV is susceptible to increased miR-199b levels, even under conditions of indirect stress such as RV pressure overload.