Figure 2.

RV Function in 6J and 6N Mice Upon PAB

(A) Representative genotyping of 6J and 6N mice by specific amplification of the nicotinamide nucleotide transhydrogenase (Nnt). 6J mice harbor an in-frame 5 exon deletion leading to a loss of exon 7-11.²⁶ Primer pair 1 (PP1) is located within the coding sequence of exon 7-11, failing to be amplified in 6J mice. Primer pair 2 (PP2) is spanning exon 7-11, resulting in a truncated fragment in 6J mice compared with the wild type Nnt fragment amplified in 6N mice. (B) Schematic demonstration of NNT function. According to Nickel et al,¹⁸ the NNT switches from forward to reversed mode under cardiac pressure overload. (C) Schematic demonstration of experimental design. PAB was performed in 6J mice lacking the NNT (Nnt^T/T) and 6N mice expressing functional active NNT (Nnt^+/+). (D) RV hypertrophy as assessed by Fulton index (n = 11/4/10/9/13/8 mice) and diastolic RV wall thickness (n = 13/13/25/17/13/8 mice) was increased upon severe PAB after 2 and 4 weeks in 6J and 6N mice. Dilation of the RV (E) and the RA (F) was augmented in 6N compared with 6J mice upon 2 and 4 weeks of PAB (n = 13/13/25/17/13/8 mice). (G) RV function as assessed from TAPSE was more impaired in 6N vs 6J mice upon PAB after 2 and 4 weeks (n = 13/13/25/17/13/8 mice). (H) Representative image of speckle tracking in 2-dimensional parasternal apical 4-chamber view for longitudinal strain analysis using Vevo strain analysis module in 6J and 6N upon PAB. (I) Strain curves (top) and corresponding quantitative strain analysis represented as heat map (bottom) of 6J and 6N mice. (J) Schematic description of sections used for analysis of longitudinal strain_total and strain RV_{free wall}(left). A strain curve was calculated for every segment. The average of strain curves (bold symbols) and the SEM (thin symbols) demonstrating deformation of RV free wall of 6J and 6N mice upon 4 weeks of PAB. One representative animal per group is shown. (K) Longitudinal strain of the RV free wall was significantly diminished in 6N compared with 6J mice upon 4 weeks of PAB. Pk = peak (n= 9/7/8/7 mice). (L) Longitudinal displacement and (M) velocity of the RV free wall was significantly decreased in 6N compared with 6J mice upon 4 weeks of PAB (n = 9/7/8/7 mice). (N) Longitudinal strain of the RV free wall negatively correlated with TAPSE reflecting RV systolic function (n = 31 mice). Statistical significance in D (Fulton index) and K to M was calculated with 1-way analysis of variance, in D (RVWT, d) to G with a marginal linear mixed effect model, followed by Bonferroni’s post hoc test. For N, Pearson correlation was tested. ∗P < 0.05; ∗∗P < 0.01; ∗∗∗P < 0.001 compared with respective control; ^#P < 0.05; ^##P < 0.01; ^###P < 0.001 compared with corresponding 6J. Abbreviations as in Figure 1.