Low and High Pressor Doses of Ang II Lead to Two Distinct Phenotypes of Hypertensive Heart Disease in Mice

FIGURE 1. A dose‐dependent induction of myocardial concentric remodeling and hypertrophy, but not hypertension, by Ang II. (A) Gradual increase in both systolic and diastolic blood pressures measured with tail‐cuff method was achieved with s.c. 0.5 or 1.5 mg/kg/day angiotensin II infusions. (B) Representative cardiac LV cross‐sections stained with HE, scale bar 2500 μm. HighA group experienced an increase in (C) overall heart weight, (D) left ventricular mass (LV mass), (E) left ventricle posterior wall in diastole (LVPWd) and in (F) in relative wall thickness, but in LowA only relative wall thickness was increased. (G) Cardiomyocyte size measured from the myocardial septum showed cell hypertrophy in HighA group. (H) Representative images of septal cardiomyocyte areas. HE staining, scale bar 50 μm. Data presented as mean ± SD (n = 6–11 mice/group; for blood pressure measurements n = 5 for all groups; Statistical analysis was performed by One‐way ANOVA with Dunnett's post hoc test (A, C, G) and paired two‐tailed Student's t test (D, E, F); for A also unpaired two‐tailed Student's t test was performed for comparison of two dose groups on same the timepoint; *p < 0.05, **p < 0.01; ***p <…

FIGURE 2. Pathological alterations in electrical conductivity of the heart in both hypertensive groups. (A) Ventricular depolarization (QRS). (B) Total ventricular depolarization and repolarization time corrected (QTc). (C) Atrial depolarization (PQ). (D) R‐wave peak. (E) ECG‐waveform transformation in LowA and HighA during the experiment. Data presented as mean ± SD (n = 7–11 mice/group; Statistical analysis was performed by One‐way ANOVA with Dunnett's post hoc test; *p < 0.05, **p < 0.01; ***p < 0.001).

FIGURE 3. Cardiac physiology assessment shows angiotensin II dose‐dependent and—independent differences in hypertensive phenotypes. (A) M‐mode of echocardiography imaging with LV measurements. (B–D) Summary of echocardiography data showing normal ejection fraction remaining within HFpEF limits throughout the study. LV filling impairment occurred in both hypertensive groups as diastolic diameters and volumes dropped significantly. (E) HighA also showed signs of a failing heart in significant drop of cardiac output. Signs of diastolic (F, G) and systolic (H) dysfunction in angiotensin groups (n = 7 in LowA; n = 11 in HighA). (I, J) QPCR analysis showed the expression of the key regulators of cardiac contractility, SERCA2 and PLN, contributing to myocardial stiffening and poor relaxation in LowA and HighA groups (n = 5 for all groups). (K) AT1R expression in the hearts. (L) Global longitudinal strain analysis from echocardiography data showing significant deformation in the LV in both dose groups. (M) Representative image of Day 0 strain analysis from the LV long‐axis view. Data presented as mean ± SD (Statistical analysis was performed by paired two‐tailed Student's t test (A–G) and One‐way…

FIGURE 4. Hypertension leads to myocardial inflammatory activation, but myocardial α‐ smooth muscle actin activation and fibrosis are detected in hypertrophic myocardium only. (A, B) Hypertension caused increase in number of MAC‐3 positive macrophages in mid‐LV by Ang II. Notice elongated shape and position of single resident‐macrophages (arrow) in sham versus rounded ones gathered within fibrotic areas of hypertensive groups (scale bar 200 μm). (C, D) Rise in α‐SMA expression and growing presence of positively stained cardiomyocytes indicate hypertensive response in the affected myocardium (scale bar 200 μm). (E, F) Significant increase in myocardial fibrosis in HighA but not LowA (Picrosirius red staining, scale bar 2.5 mm). Data presented as mean ± SD (n = 7–11 mice/group; Statistical analysis was performed by One‐way ANOVA with Dunnett's post hoc test; *p < 0.01, ***p < 0.001).

FIGURE 5. Impaired macrovascular and microvascular structure and function contribute to diastolic dysfunction in the presence and absence of left ventricular hypertrophy. (A) Aortic root diameter was imaged with echocardiography and measured from the modified parasternal long axis view in B‐mode from the proximal ascending aorta during the onset of ventricular depolarization. (B, C) Changes in both aortic strain and stiffness index demonstrate loss of aortic wall elasticity in LowA. (D) Accumulation of perivascular collagen. (E) Coronary artery intima‐media (IM) thickening. (F) Representative images of coronary arteries stained with Picrosirius red and α‐SMA show ongoing remodeling of vascular walls (scale bars on all images 100 μm). (G) Podocalyxin‐positive endothelial area was measured demonstrating overall decrease in mid‐LV capillary number. (H, I) Also, regional differences in capillary areas were noticed within the myocardium. Data presented as mean ± SD (n = 7–11 mice/group; Statistical analysis was performed by paired two‐tailed Student's t test (A–C) and One‐way ANOVA with Dunnett's post hoc test (D, E, G, I); *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001). Ao, aorta; IM,…

FIGURE 6. Renal glomerular enlargement is dependent on Ang II dose, but not renal AT1R expression or systemic hypertension. (A) Representative HE staining of Bowman's capsules. (B) Dose‐dependent increase seen in glomerulus to Bowman's capsule ratio (scale bar 100 μm). (C, D) Kidney filtration capacity decline was seen in increased levels of plasma creatinine and urea. (E, F) No change in albumin or total protein levels was detected. (G) QPCR showed no difference in AT1R expression between hypertensive groups and controls. Data presented as mean ± SD (n = 7–11 mice/group; Statistical analysis was performed by One‐way ANOVA with Dunnett's post hoc test; for glomeruli pathology, 36–68 filtrating units were measured and averaged; *p < 0.05, **p < 0.01, ***p < 0.001). AT1R, Angiotensin II type 1a receptor.