Biventricular Remodeling in Murine Models of Right Ventricular Pressure Overload

<div><p></p><p>Right ventricular (RV) failure is a major cause of mortality in acute or chronic lung disease and left heart failure. The objective of this study was to demonstrate a percutaneous approach to study biventricular hemodynamics in murine models of primary and secondary RV pressure overload (RVPO) and further explore biventricular expression of two key proteins that regulate cardiac remodeling: calcineurin and transforming growth factor beta 1 (TGFβ1).</p><p>Methods</p><p>Adult, male mice underwent constriction of the pulmonary artery or thoracic aorta as models of primary and secondary RVPO, respectively. Conductance catheterization was performed followed by tissue analysis for changes in myocyte hypertrophy and fibrosis.</p><p>Results</p><p>Both primary and secondary RVPO decreased biventricular stroke work however RV instantaneous peak pressure (dP/dt_max) and end-systolic elastance (Ees) were preserved in both groups compared to controls. In contrast, left ventricular (LV) dP/dt_max and LV-Ees were unchanged by primary, but reduced in the secondary RVPO group. The ratio of RV:LV ventriculo-arterial coupling was increased in primary and reduced in secondary RVPO. Primary and secondary RVPO increased RV mass, while LV mass decreased in primary and increased in the secondary RVPO groups. RV fibrosis and hypertrophy were increased in both groups, while LV fibrosis and hypertrophy were increased in secondary RVPO only. RV calcineurin expression was increased in both groups, while LV expression increased in secondary RVPO only. Biventricular TGFβ1 expression was increased in both groups.</p><p>Conclusion</p><p>These data identify distinct effects of primary and secondary RVPO on biventricular structure, function, and expression of key remodeling pathways.</p></div

Fibrotic remodeling in models of primary and secondary right ventricular pressure overload (RVPO).

<p>A) Picrosirius red staining for collagen abundance and B) quantitation of percent fibrosis in the right (RV) and left ventricle (LV) after primary and secondary RVPO. C) Western blot and D) bar graph of Type I collagen normalized to GAPDH. E–F) Gene expression of transforming growth factor beta 1 (TGFβ1) and endoglin normalized to ribosomal RNA (rRNA). G–H) Quantified protein expression of phosphorylated ERK (pERK) normalized to total ERK and phosphorylated Smad-3 normalized to total Smad-3. *, p<0.05 vs Sham for the corresponding ventricle; †, p<0.05 vs Primary RVPO for the corresponding ventricle; ‡, p<0.05 vs the RV for the same RVPO condition.</p

Hypertrophic remodeling in models of primary and secondary right ventricular pressure overload (RVPO).

<p>A) Representative histologic staining of right (RV) and left (LV) ventricular tissue and B) bar graph of RV and LV cardiomyocyte cross-sectional areas after primary and secondary RVPO. C) Western blot and D) bar graph of RV and LV calcineurin protein expression normalized to GAPDH. E) Calcineurin-Aβ (CN-PP), F) brain natriuretic peptide (BNP), G) beta-myosin heavy chain (b-MHC), and H) sarcoplasmic reticulum Ca²⁺ATPase (SERCa) gene expression normalized to total ribosomal RNA (rRNA). *, p<0.05 vs Sham for the corresponding ventricle; †, p<0.05 vs Primary RVPO for the corresponding ventricle; ‡, p<0.05 vs the RV for the same RVPO condition.</p

Biventricular conductance catheterization in a closed-chest, non-invasively ventilated mouse.

<p>A) Hemodynamic tracings illustrating pressure volume (PV) catheters tracking from the right atrium (RA) to right ventricle (RV) via the right external jugular vein and aorta (Ao) to left ventricle (LV) via the right carotid artery via a suprasternal incision in a closed-chest mouse (*, salivary gland). B) Representative steady-state PV loops in mouse models of (i) primary and (ii) secondary right ventricular pressure overload (RVPO) (blue loops represent sham operated animals).</p

Biventricular (BiV) ventriculo-arterial coupling ratios of arterial elastance (Ea) and end-systolic elastance (Ees) in the right (RV) and left ventricles (LV) using models of primary and secondary right ventricular pressure overload (RVPO).

*<p>p<0.05: Sham RV vs Sham LV.</p>§<p>p<0.05: Primary RVPO RV vs LV.</p>†<p>p<0.05: Sham RV vs Primary or Secondary RVPO RV.</p>#<p>p<0.05:Secondary RVPO RV vs LV.</p>‡<p>p<0.05: Sham LV vs Primary or Secondary RVPO LV.</p

Biventricular hemodynamics in models of primary and secondary right ventricular pressure overload (RVPO).

<p>A) Peak systolic pressure, B) End-diastolic pressure, C) Heart rate, D) End-diastolic volume, E) End-systolic volume, F) Stroke volume, G) dP/dt max, H) Ventricular stroke work, and I) Cardiac output. *, p<0.05 vs Sham for the corresponding ventricle; †, p<0.05 vs Primary RVPO for the corresponding ventricle; ‡, p<0.05 vs the RV for the same RVPO condition.</p

Total body, lung, and right (RV) and left (LV) ventricular weights normalized to tibia length in models of primary and secondary right ventricular pressure overload (RVPO).

*<p>p<0.05 vs Sham.</p>†<p>p<0.05, vs Primary RVPO.</p

Effects on angiogenic peptide levels of UFH and bivalirudin <i>in vivo</i> in wild type C57/Bl6 mice.

<p>Treatment with UFH for 30 minutes resulted in a rapid and significant increase in mouse serum sFlt1 (A) and PGF (B) levels (>500% increase, p<0.01, for both) compared to normal saline vehicle. UFH also produced a modest but significant increase in mouse VEGF₁₆₅ (C) levels (221+101%, p<0.05). Treatment with DSO4 did not influence sFlt1 or PlGF levels. VEGF₁₆₅ levels were modestly increased by DSO4 treatment. Bivalirudin treatment had no effect on sFlt1, PlGF, and VEGF₁₆₅ levels. sEng (D) levels were mildly increased with vehicle, UFH, bivalirudin and DSO4, with no significant differences between the 4 treatments.</p

Subject Characteristics.

<p>Subject Characteristics.</p

Effects on angiogenic peptides of UFH (dotted lines) and bivalirudin (dashed lines) in human subjects undergoing PCI.

<p>sFlt1 (A) and PlGF (B) were significantly increased by UFH but not bivalirudin, VEGF₁₆₅ (C) was significantly decreased by UFH but not bivalirudin, and sEng (D) was unchanged with both UFH and bivalirudin.</p