Search

ELK3 is upregulated in blood and pulmonary vascular cells of PAH patients and may play a significant role in PAH potentially through modulating BMPR2 signaling.

Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal dominant disease that causes arteriovenous vascular malformations (AVMs) in different organs, including the lung. Three genes, ENG (endoglin), ACVRL1 (ALK1) and SMAD4, all members of the TGF-β/BMPR2 signaling pathway, are responsible for over 85% of all HHT cases. However, how these loss-of-function gene mutations lead to AVMs formation and what common downstream signaling they target is unknown. Here, using a combination of siRNA-mediated gene silencing, whole transcriptomic RNA sequencing, bioinformatic analysis, transcriptomic-based drug discovery, endothelial cells functional assays and VEGF signaling analysis, andex vivoprecision cut lung slice (PCLS) cultures approach, we uncovered common downstream transcriptomic gene signatures of HHT-casing genes and identified promising drug for HHT. We found the commonly used BMPR2-signaling downstream target ID1 is not a common downstream target of all the three HHT genes knockdown in human pulmonary microvascular endothelial cells (PMVECs). We identified novel common downstream targets of all the three HHT-causing genes that were enriched for HHT-related biological process and signaling pathways. Among those downstream genes, LYVE1, GPNMB, and MC5R were strong downstream targets that could serve as a better common downstream target than ID1. Furthermore, using the common downstream upregulated genes (HHT disease signature) following HHT gene knockdown, we identified a small molecule drug, Brivanib, that reversed the HHT disease signature, and inhibited VEGF-induced ERK1/2 phosphorylation, proliferation, and angiogenesis in PMVECs and inhibited some of the upregulated HHT disease genes in PCLS. Our findings suggest that Brivanib could be an emerging new drug for HHT.

This study shows that the long non-coding RNA RGMB-AS1 is upregulated in the blood and pulmonary vascular cells of PAH patient and that it regulates BMPR2 signaling. Inhibiting RGMB-AS1 increases BMPR2 signaling and improves pulmonary vascular cell function.

Introduction: The left ventricle (LV) is known to transfer kinetic mechanical energy to the right ventricle (RV) during systole. Normally, the RV relies on this mechanical assistance for up to 70% of its pressure generation. However, this biventricular relationship and its effect on RV function has not been explored in the progression in the pressure overloaded RV. In this study, we developed a longitudinal mouse model of pulmonary arterial (PA)-banding concomitant with transverse aortic constriction (TAC) to initiate an adaptive LV remodeling response. We hypothesized that adaptive LV remodeling would improve RV systolic function in an RV pressure overloaded setting. Methods: Surgical PAB was performed on mice to induce RV pressure overload and myocardial remodeling. Mild surgical TAC was performed on these mice 2-weeks (w) post-PAB. Steady-state free precession (SSFP) cardiac magnetic resonance (CMR) imaging (SSFP-CMR) was performed at 1w post-PAB, 1 w post-TAC (PAB-TAC) and 4 w and 7 w post-surgery (n=7). As controls we used Sham (n=5), TAC-only (n=4, TAC) as well as PAB-only (n=4, PAB) mice at 1, 4, and 7 w after surgery. These images were analyzed using feature-tracking (FT) software to compute measurements of ventricular volumes. Results: RV ejection fraction (RVEF) was reduced in PAB mice compared to Sham at 1w (p=0.02, 0.38±0.06 versus 0.52±0.08, respectively). After TAC, PAB-TAC mice showed an increase in RVEF compared to PAB-only mice at 4 w (p=0.03, 0.49±0.04 versus 0.39±0.08, respectively), and at 7 w (p=0.001, 0.50±0.06 versus 0.37±0.1, respectively). Similarly, tricuspid annular plane systolic excursion (TAPSE) showed a decrease in PAB mice compared to sham (p=0.002, 0.85±0.15mm versus 1.73±0.33mm, respectively) and an increase after TAC at 2 w (p=0.001, 1.55±0.29mm versus 0.85±0.15mm, respectively), 4 w (p=0.002, 1.75±0.32mm versus 0.93±0.21mm, respectively), and at 7 w post-surgery (p=0.001, 1.70±0.33mm versus 0.91±0.14mm, respectively). Conclusions: Even though LV-to-RV mechanical energy transfer is well established in normotensive animals, our data supports a mechanistic link between RV systolic function and LV pressure in remodeled and pressure-overloaded RVs.

Introduction: Right ventricular (RV) function determines the prognosis of pulmonary hypertension. Capillary rarefaction using 2D imaging has been proposed as the hallmark of RV failure, although this paradigm is controversially discussed. By applying 3D deep-tissue imaging, we characterized the adaptive and maladaptive response of the capillaries in the pressure-overloaded RV in hypertrophy and failure. Methods and Results: Mice subjected to pulmonary artery banding (PAB) were harvested after 3 weeks (w) (compensated RV hypertrophy) and 7w post-surgery (decompensated RV failure). Hearts were sectioned into 250 μm and capillaries were stained with isolectin B4. Samples were imaged with confocal microscopy and reconstructed into 3D using Imaris imaging software (Fig. A, n=4). In the RV free wall, mean capillary length decreased, and branching, tortuosity, mean and total capillary diameter increased 3w post-PAB. Mean and total diameter, and total length decreased at 7w resulting in a reduced capillary volume normalized to heart volume at 7w vs 3w, but not significantly reduced vs baseline suggesting that this is not the mechanism of RV failure (Fig. B). However, most strikingly we uncovered by sparsely labeling cardiomyocytes that the capillary-cardiomyocyte contact surface was maintained at w3, yet significantly decreased in areas of interstitial fibrosis in the decompensated RV at 7w compared to baseline and 3w (Fig. C, D). Conclusions: 3D deep-tissue imaging uncovered the remarkable adaptive response of the RV microvasculature in the pressure-overloaded RV to maintain an adequate capillary-cardiomyocyte contact by increasing capillary branching, length and diameter. These mechanisms failed in the decompensating RV when interstitial fibrosis impaired the capillary-cardiomyocyte interaction. Our method offers the unprecedented opportunity to study microvascular adaption in the pressure overloaded RV and is readily transferable to human tissue.