Raff, G. W. | bioRxiv Science

bioRxiv2025

Pulmonary Vascular Endothelial Dysfunction is Induced by Non-Pulsatile Pulmonary Blood Flow in an Ovine Classic Glenn Model

Structured AbstractO_ST_ABSBackgroundC_ST_ABSPulmonary vascular disease (PVD) in patients with single ventricular heart disease following the partial cavalpulmonary connection (Glenn) is a significant source of morbidity. However, the etiology of pulmonary vascular endothelial cell (EC) dysfunction, an established precursor to PVD, is incompletely understood but may involve abnormal blood flow patterns, hypoxemia, and polycythemia. HypothesisUtilizing an ovine Glenn model, we hypothesized that non-pulsatile pulmonary blood flow (PBF) induces pulmonary vascular EC dysfunction, independent of hypoxemia or polycythemia. MethodsSeven lambs (6-8 weeks old) underwent a Glenn procedure. Eight weeks later, Glenn and age-matched controls were studied. The response to the endothelium-dependent vasodilator acetylcholine (Ach) was determined in isolated pulmonary arteries (PA). Nitric oxide (NO) and endothelin-1 (ET-1) signaling was determined in right lung tissues. Indices of cell proliferation, angiogenesis, and apoptosis were determined in PA endothelial cells (PAECs). Comparisons were made by unpaired t-test and ANOVA. ResultsThere were no differences in age, hemoglobin, or oxygen saturation between groups. Mean PA pressure and left PA flow were higher, and right lung blood flow was lower in Glenn lambs compared to controls (p<0.05). All other baseline hemodynamics were similar. Glenn PAs had impaired relaxation to Ach. Glenn lung NO metabolite levels (NOx) and eNOS protein were lower, and ET-1 levels and prepro-ET-1 protein were higher than controls (p<0.05). Glenn PAECs had higher rates of proliferation and angiogenesis, and decreased apoptosis (p < 0.05). ConclusionsThe initiation of non-pulsatile PBF following the Glenn induces early EC dysfunction independent of hypoxemia and polycythemia.

physiology↗

bioRxiv2024

Microvascular preservation and cardiomyocyte hyperplasia underlie adaptive right ventricular development in congenital heart disease-associated pulmonary arterial hypertension

AbstractO_ST_ABSBackgroundC_ST_ABSRight ventricular (RV) failure is the primary cause of death among patients with pulmonary arterial hypertension (PAH). Patients with congenital heart disease- associated PAH (CHD-PAH) demonstrate improved outcomes compared to patients with other forms of PAH, which is related to the maintenance of an adaptively hypertrophied RV. In an ovine model of CHD-PAH, we aimed to elucidate the cellular, microvascular, and transcriptional adaptations to congenital pressure overload that support RV function in CHD-PAH. MethodsFetal surgery was performed on late gestation lambs to insert a large aortopulmonary graft, leading to a persistent congenital left-right shunt and RV pressure load. At 3 days and 4-6 weeks of life, shunt RV microvasculature, cardiomyocyte structure, and myocardial growth mechanisms were compared to age-matched controls and unoperated fetal RV. RNA sequencing was performed to assess differences in the RV transcriptomes. ResultsAt 4-6 weeks of age, shunt lambs demonstrate significant RV enlargement (shunt 37.1 {+/-} 2.9g vs control 15.9 {+/-} 1.0g, p<0.001) but maintain stable microvascular density (fetal 3.0 {+/-} 0.6 vs shunt 2.9 {+/-} 0.3 vs control 3.1 {+/-} 0.6 capillaries per 1000 {micro}m3, p>0.05). Shunt RV cardiomyocytes are significantly smaller by cross-sectional area and more numerous than age-matched controls (shunt 73.3 {+/-} 5.5 {micro}m2 vs control 99.2 {+/-} 4.9 {micro}m2, p=0.013). At 3 days, shunt RV cardiomyocytes show evidence of increased proliferative capacity and ongoing hyperplasia compared to controls. RNA sequencing analyses reveal a distinct gene expression profile in shunt RV consistent with a delay in terminal differentiation and metabolic adaptations to support adaptive function. ConclusionsThis study provides novel insights into the development of adaptive RV hypertrophy in CHD-PAH, demonstrating roles for preserved microvascular density and increased postnatal cardiomyocyte hyperplasia in supporting RV performance. Future investigations into the mechanisms underlying these changes could have significant implications for the development of novel therapeutic strategies for supporting RV function.

physiology↗