Pathology of pulmonary hypertension

Female Fibroblast Activation Is Estrogen-Mediated in Sex-Specific 3D-Bioprinted Pulmonary Artery Adventitia Models

Pulmonary arterial hypertension (PAH) is a form of pulmonary vascular disease characterized by scarring of the small blood vessels that results in reduced blood flow and increased blood pressure in the lungs. Over time, this increase in blood pressure causes damage to the heart. Idiopathic (IPAH) impacts male and female patients differently, with female patients showing a higher disease susceptibility (4:1 female-to-male ratio) but experiencing longer survival rates postdiagnosis compared to male patients. This complex sex dimorphism is known as the estrogen paradox. Prior studies suggest that estrogen signaling may be pathologic in the pulmonary vasculature and protective in the heart, yet the mechanisms underlying these sex differences in IPAH remain unclear. Many previous studies of PAH relied on male cells or cells of undisclosed origin for in vitro modeling. Here, we present a dynamic, three-dimensional (3D)-bioprinted model incorporating cells and circulating sex hormones from female patients to specifically study how female patients respond to changes in microenvironmental stiffness and sex hormone signaling on the cellular level. Poly(ethylene glycol)-α methacrylate (PEGαMA)-based hydrogels containing female human pulmonary artery adventitia fibroblasts (hPAAFs) from IPAH or control donors were 3D bioprinted to mimic pulmonary artery adventitia. These biomaterials were initially soft, like healthy blood vessels, and then stiffened using light to mimic vessel scarring in PAH. These 3D-bioprinted models showed that stiffening the microenvironment around female IPAH hPAAFs led to hPAAF activation. On both the protein and gene-expression levels, cellular activation markers significantly increased in stiffened samples and were highest in IPAH patient-derived cells. Treatment with a selective estrogen receptor modulator, which is currently in clinical trials for IPAH treatment, reduced the expression of hPAAF activation markers, demonstrating that hPAAF activation is one pathologic response mediated by estrogen signaling in the vasculature. These results showed the utility of sex-specific, 3D-bioprinted pulmonary artery adventitia models for preclinical drug discovery and validation.

Extracellular matrix dynamics in a rat model of pulmonary arterial hypertension: unveiling the role of hyaluronan in disease pathology

OBJECTIVE

We aimed to investigate the feasibility of conducting extracellular matrix studies within this rat model.

MATERIALS AND METHODS

This study involved 24 Sprague Dawley rats, divided into two groups. Group 1 served as the normoxia control, while Group 2 is SU-5416 pulmonary arterial hypertension (PAH) model. Pulmonary artery pressure (PAP) was measured in both groups using a micro-catheter Power Lab device. Hyaluronan (HA) plasma level was quantified through ELISA, and HA levels were determined via lung tissue immunostaining. Western blotting detected protein levels, and real-time RT-PCR assessed mRNA expressions for HAS1, HAS2, and HAS3 and hyal1 and hyal2.

RESULTS

HA plasma levels were markedly higher in PAH rats compared to controls (HA ng/ml, mean ± SD: PAH 3.8 ± 0.41, control 1.96 ± 0.31, P  < 0.0015). Protein analysis showed no detection of HAS1 and HAS3 proteins in both groups, while HAS2 protein expression was notably higher in PAH rats than controls (HAS2 levels, mean ± SD: PAH 2.0 ± 0.5, control 0.86 ± 0.07, P  = 0.0493). Hyal2 protein expression remained consistent between groups (Hyal2 levels, mean ± SD: PAH 1.41 ± 0.18, control 1.05 ± 0.14, P  = 0.214). No mRNA expression of HAS1, HAS3, and Hyal1 were detected in both groups, Hyal2 expression was identified in both without differences. HAS2 mRNA expression was present in both groups, with a significantly higher increase observed in the hypoxia SU-5416 PAH rat model compared to controls.

CONCLUSION

Establishing an extracellular matrix profile in the rat model, resembling human PAH under hypoxia SU-5416 conditions, highlights the model's suitability for matrix studies.

Identification of nitric oxide-related key genes in pulmonary hypertension via bioinformatics and in vitro validation for therapeutic target discovery

This study aims to uncover key genes and associated pathways related to nitric oxide (NO) in pulmonary hypertension (PH). By analyzing datasets GSE131793 and GSE703 from the Gene Expression Omnibus (GEO), differentially expressed genes (DEGs) associated with PH were identified. NO-related genes were selected from the GeneCards database and intersected with the DEGs. Subsequently, Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analyses were conducted to evaluate pathway enrichment, and key genes were selected using the random forest and least absolute shrinkage and selection operator (LASSO) regression algorithms. Immune cell infiltration was analyzed using the CIBERSORT algorithm, and Gene Set Enrichment Analysis (GSEA) was performed to explore potential mechanisms. The transcriptional regulatory networks of key genes were constructed using Cytoscape software. The expression levels of the key genes were validated in peripheral blood samples from PH patients using quantitative real-time PCR (RT-qPCR). A total of 97 DEGs were identified, of which 20 were NO-related genes. Three key genes, HBG2, PRKAB1, and THBD, were further selected. RT-qPCR results revealed significant upregulation of HBG2 and THBD, and downregulation of PRKAB1 in PH patients. CIBERSORT analysis indicated the significant role of immune cells in the pathology of PH. GSEA and transcriptional network analyses further suggested that key genes may participate in the pathogenesis of PH through immune regulation and metabolic pathways. Through bioinformatics analysis and clinical sample validation, this study systematically elucidates the potential mechanisms of NO-related key genes in PH, providing new molecular targets for early diagnosis and targeted therapy of PH.

Hypoxia responses in arginase 2 deficient mice enhance cardiovascular health

RATIONALE

Physiological responses to hypoxia involve adaptations in the hematopoietic and cardiovascular systems, which work together to ensure adequate oxygen delivery to tissues for energy production. The arginine/nitric oxide (NO) pathway regulates both systems through its effects on erythropoiesis and vasodilation. In Tibetan populations native to high-altitude hypoxia, increased NO production from arginine and decreased arginine metabolism by arginase contribute to these adaptive mechanisms. These metabolic changes enhance tissue oxygen delivery and reduce the risk of hypoxic pulmonary hypertension. Here, we hypothesize that genetic deletion of mitochondrial arginase 2 ( Arg2 ) in mice will enhance cardiovascular effects and mitigate hypoxia-induced pulmonary hypertension.

METHODS

Complete blood counts, bone marrow erythroid differentiation, plasma arginine and NO (measured as nitrite), right ventricular systolic pressure (RVSP), heart rate, heart weight, and blood pressure were measured in wild-type (WT) and Arg2 knockout ( Arg2 KO) mice exposed to short-term (6, 12, 48, or 72 hours) or long-term (3 weeks) hypoxia.

RESULTS

Under normoxic conditions, Arg2 KO and WT mice exhibit similar RBC counts, hemoglobin levels, hematocrit, heart rate, systolic and diastolic blood pressures, and heart weight (all P > 0.05). WT mice increase erythropoiesis at 12 hours of hypoxia, including proerythroblasts (stage I, P = 0.004), polychromatic erythroblasts (stage III, P = 0.0004), and orthochromatic erythroblasts (stage IV, P = 0.03), but Arg2 KO mice do not increase erythropoiesis. After 48 hours of hypoxia, Arg2 KO mice increase proerythroblasts (stage I, P = 0.0008), but levels remain significantly lower than in WT mice. Plasma arginine and NO levels increase under hypoxia. NO levels peak at 12 hours of hypoxia in WT mice, then decline rapidly. In contrast, NO levels in Arg2 KO mice are higher than in WT mice, with sustained elevations at 48 hours of hypoxia ( P = 0.03). Arg2 KO mice have significantly higher plasma arginine levels than WT at 6, 12, and 72 hours of hypoxia (all P < 0.05). Under chronic hypoxia, Arg2 KO and WT mice show similar RBC counts, hemoglobin levels, hematocrit, and NO levels. Unlike WT, Arg2 KO mice do not increase RVSP ( P = 0.4) and have lower mean arterial ( P = 0.03) and diastolic blood pressures ( P = 0.01), as well as much lower heart rates ( P < 0.0001). Additionally, small blood vessels increase in lungs of Arg2 KO mice (CD31, P = 0.02; vWF, P = 0.6).

CONCLUSIONS

Arginine metabolism in the mitochondria plays a key role in modulating adaptive responses to hypoxia. Deletion of Arg2 results in delayed erythropoiesis under acute hypoxia, but better cardiovascular health, as indicated by higher levels of nitrite and arginine, and lower RVSP, blood pressure, and heart rate with chronic hypoxia.

Changes in Macrophages in Pulmonary Hypertension: A Focus on High-altitude Pulmonary Hypertension

High-altitude pulmonary hypertension (HAPH) is a condition characterized by elevated pulmonary arterial pressure exceeding normal physiological values, resulting from a combination of high-altitude low-pressure, hypoxic environments, genetic susceptibility, immune dysfunction, and neurogenic disturbances. This condition predominantly manifests as right heart failure, severely impacting quality of life and life expectancy. Macrophages, as one of the most prevalent innate immune cells, have been increasingly recognized for their crucial role in the pathogenesis of HAPH. The low-pressure and hypoxic environment, along with other etiological factors, lead to metabolic abnormalities in tissue cells and the microenvironment. This results in increased secretion of chemokines, cytokines, and growth factors in the microenvironment, which promote the proliferation of tissue-resident macrophages and the differentiation of monocytes recruited from the blood into macrophages. This exacerbates the inflammatory cascade, further promoting cell proliferation, tissue repair, and inhibition of apoptosis. These processes contribute to the migration and proliferation of pulmonary arterial smooth muscle cells, endothelial cells, and fibroblasts, leading to vascular remodeling and ultimately the development of pulmonary arterial hypertension. This review examines the role of macrophage-mediated immune responses in high-altitude pulmonary arterial hypertension, with a focus on hypoxia as a key feature.

Pathology of Pulmonary Vascular Disease with Radiologic Correlation

Pulmonary hypertensive changes are commonly seen by the surgical pathologist, but the majority represents secondary changes due to some process extrinsic to the lung. Some primary, or idiopathic, vascular diseases result in unique pathologic changes including the plexiform lesion and venous hypertensive changes. Thromboembolic disease also shows unique pathologic features. Diffuse alveolar hemorrhage, vasculitis, and capillaritis often overlap, but may represent separate, distinct pathologic processes. Lastly, alveolar capillary dysplasia with misalignment of pulmonary veins, as well as chronic lung allograft vasculopathy, present as unique pathologies in the neonate and posttransplant recipient, respectively.

Female fibroblast activation is estrogen-mediated in sex-specific 3D-bioprinted pulmonary artery adventitia models

Pulmonary arterial hypertension (PAH) impacts male and female patients in different ways. Female patients exhibit a greater susceptibility to disease (4:1 female-to-male ratio) but live longer after diagnosis than male patients. This complex sexual dimorphism is known as the estrogen paradox. Prior studies suggest that estrogen signaling may be pathologic in the pulmonary vasculature and protective in the heart, yet the mechanisms underlying these sex-differences in PAH remain unclear. PAH is a form of a pulmonary vascular disease that results in scarring of the small blood vessels, leading to impaired blood flow and increased blood pressure. Over time, this increase in blood pressure causes damage to the heart. Many previous studies of PAH relied on male cells or cells of undisclosed origin for in vitro modeling. Here we present a dynamic, 3D-bioprinted model that incorporates cells and circulating sex hormones from female patients to specifically study how female patients respond to changes in microenvironmental stiffness and sex hormone signaling. Poly(ethylene glycol)-alpha methacrylate (PEGαMA)-based hydrogels containing female human pulmonary artery adventitia fibroblasts (hPAAFs) from idiopathic PAH (IPAH) or control donors were 3D bioprinted to mimic pulmonary artery adventitia. These biomaterials were initially soft, like healthy blood vessels, and then stiffened using light to mimic vessel scarring in PAH. These 3D-bioprinted models showed that stiffening the microenvironment around female IPAH hPAAFs led to hPAAF activation. On both the protein and gene-expression levels, cellular activation markers significantly increased in stiffened samples and were highest in IPAH patient-derived cells. Treatment with a selective estrogen receptor modulator reduced expression hPAAF activation markers, demonstrating that hPAAF activation is a one pathologic response mediated by estrogen signaling in the vasculature, validating that drugs currently in clinical trials could be evaluated in sex-specific 3D-bioprinted pulmonary artery adventitia models.

Automated volumetry of core and peel intrapulmonary vasculature on computed tomography angiography for non-invasive estimation of hemodynamics in patients with pulmonary hypertension (2022 updated hemodynamic definition)

Background

Computed tomography pulmonary angiography (CTPA) is frequently performed in patients with pulmonary hypertension (PH) and may aid non-invasive estimation of pulmonary hemodynamics. We, therefore, investigated automated volumetry of intrapulmonary vasculature on CTPA, separated into core and peel fractions of the lung volume and its potential to differentially reflect pulmonary hemodynamics in patients with pre- and postcapillary PH.

Methods

A retrospective case-control study of 72 consecutive patients with PH according to the 2022 joint guidelines of the European Society of Cardiology and the European Respiratory Society who underwent right heart catheterization (RHC) and CTPA within 7 days between August 2013 and February 2016 at Thoraxklinik at Heidelberg University Hospital (Heidelberg, Germany) was conducted. Vessel segmentation was performed using the in-house software YACTA. Vascular volumes in different core and peel fractions of the lung were corrected for body surface area. Spearman correlation coefficients with mean pulmonary arterial pressure (mPAP), pulmonary arterial wedge pressure (PAWP) and pulmonary vascular resistance (PVR) were calculated, and a linear regression analysis was done to account for potential confounders.

Results

Median age of the study sample was 71.5 years [interquartile range (IQR), 60.0-77.0 years], 48 (66.67%) were female. Median mPAP was 35.5 mmHg (IQR, 27.0-47.2 mmHg). Postcapillary PH was present in 24/72 (33.3%) patients and precapillary PH in 48/72 (66.7%) patients. Moderate to strong correlations between core intrapulmonary vessel volumes and mPAP were observed in postcapillary PH patients with a maximum at 50% core lung volume (r=0.71, P<0.001). No significant influence of age or sex on this relationship was identified. Correlation with RHC measurements was weak or negligible in patients with precapillary PH.

Conclusions

Automated volumetry of vessels in the core lung strongly correlated with mPAP in patients with postcapillary PH and has potential for non-invasive assessment of postcapillary PH in patients undergoing CTPA.

Deciphering the inhibitory effects of trimetazidine on pulmonary hypertension development via decreasing fatty acid oxidation and promoting glucose oxidation

Pulmonary hypertension (PH) is a devastating disease characterized by vascular remodeling, resulting in right ventricular failure and death. Dysregulation of energy metabolism is linked to PH pathogenesis. Trimetazidine (TMZ), a selective long-chain 3-ketoacyl coenzyme A thiolase inhibitor, is critical in maintaining energy metabolism. Despite the indicated TMZ's inhibitory effect on pulmonary vascular remodeling in PH development, the integrated evaluation of the changes in biomolecules, such as metabolites and transcripts, that TMZ induces in the lung and heart tissues is largely unknown in vivo. For an improved understanding of the molecular mechanism involving the effects of TMZ on PH development, we performed a comprehensive analysis of the changes in cardiac metabolites and pulmonary transcripts of SU5416-Hypoxia (Su/Hx) rats treated with TMZ. Metabolomic analysis of the Su/Hx-induced PH hearts demonstrated that TMZ reduced the long-chain fatty acid concentration. Additionally, TMZ alleviated PH degree and excessive strain on the right heart functions in rats with Su/Hx-induced PH. We identified the candidate target genes for TMZ treatment during PH development. Interestingly, the mRNA levels of the fatty acid transporters were substantially downregulated by TMZ administration in the lungs with Su/Hx-induced PH. Notably, TMZ suppressed excessive proliferation of human pulmonary artery smooth muscle cells under hypoxic conditions. Our study suggests that TMZ ameliorates PH development by involving energy metabolism in the lungs and heart.

mTOR in the Development of Hypoxic Pulmonary Hypertension Associated with Cardiometabolic Risk Factors

The pathophysiology of pulmonary hypertension is complex and multifactorial. It is a disease characterized by increased pulmonary vascular resistance at the level due to sustained vasoconstriction and remodeling of the pulmonary arteries, which triggers an increase in the mean pulmonary artery pressure and subsequent right ventricular hypertrophy, which in some cases can cause right heart failure. Hypoxic pulmonary hypertension (HPH) is currently classified into Group 3 of the five different groups of pulmonary hypertensions, which are determined according to the cause of the disease. HPH mainly develops as a product of lung diseases, among the most prevalent causes of obstructive sleep apnea (OSA), chronic obstructive pulmonary disease (COPD), or hypobaric hypoxia due to exposure to high altitudes. Additionally, cardiometabolic risk factors converge on molecular mechanisms involving overactivation of the mammalian target of rapamycin (mTOR), which correspond to a central axis in the development of HPH. The aim of this review is to summarize the role of mTOR in the development of HPH associated with metabolic risk factors and its therapeutic alternatives, which will be discussed in this review.

Not Just CTEPH: A Narrative Review on the Spectrum Approach to Postpulmonary Embolism Conditions

Three mutually exclusive entities can underlie a postpulmonary embolism syndrome (PPES): not obstructed postpulmonary embolism syndrome (post-PE dyspnea), chronic thromboembolic pulmonary disease (CTEPD), and chronic thromboembolic pulmonary hypertension (CTEPH). Cardiorespiratory impairment in CTEPH and CTEPD underlies respiratory and hemodynamic mechanisms, either at rest or at exercise. Gas exchange is affected by the space effect, the increased blood velocity, and, possibly, intracardiac right to left shunts. As for hemodynamic effects, after a period of compensation, the right ventricle dilates and fails, which results in retrograde and anterograde right heart failure. Little is known on the pathophysiology of post-PE dyspnea, which has been reported in highly comorbid with lung and heart diseases, so that a "two-hit" hypothesis can be put forward: it might be caused by the acute myocardial damage caused by pulmonary embolism in the context of preexisting cardiac and/or respiratory diseases. More than one-third of PE survivors develops PPES, with only a small fraction (3-4%) represented by CTEPH. A value of ≈3% is a plausible estimate for the incidence of CTEPD. Growing evidence supports the role of CTEPD as a hemodynamic phenotype intermediate between post-PE dyspnea and CTEPH, but it still remains to be ascertained whether it constantly underlies exercise-induced pulmonary hypertension and if it is a precursor of CTEPH. Further research is needed to improve the understanding and the management of CTEPD and post-PE dyspnea.

Pulmonary Hypertension: Pharmacological and Non-Pharmacological Therapies

Pulmonary hypertension (PH) is a severe and chronic disease characterized by increased pulmonary vascular resistance and remodeling, often precipitating right-sided heart dysfunction and death. Although the condition is progressive and incurable, current therapies for the disease focus on multiple different drugs and general supportive therapies to manage symptoms and prolong survival, ranging from medications more specific to pulmonary arterial hypertension (PAH) to exercise training. Moreover, there are multiple studies exploring novel experimental drugs and therapies including unique neurostimulation, to help better manage the disease. Here, we provide a narrative review focusing on current PH treatments that target multiple underlying biochemical mechanisms, including imbalances in vasoconstrictor-vasodilator and autonomic nervous system function, inflammation, and bone morphogenic protein (BMP) signaling. We also focus on the potential of novel therapies for managing PH, focusing on multiple types of neurostimulation including acupuncture. Lastly, we also touch upon the disease's different subgroups, clinical presentations and prognosis, diagnostics, demographics, and cost.

Unraveling the genetic landscape of pulmonary arterial hypertension in Indian patients: A transcriptome study

BACKGROUND

Pulmonary hypertension (PH) is the abnormal elevation of pressure in the pulmonary vascular system, with various underlying causes. A specific type of PH is pulmonary arterial hypertension (PAH), a severe condition characterized by high pulmonary arterial pressure resulting from structural changes in distal pulmonary vessels, altered arterial tone, and inflammation. This leads to right ventricular hypertrophy and heart failure. The molecular mechanisms behind PAH are not well understood. This manuscript aims to elucidate these mechanisms using the genetic tool, aiding in diagnosis and treatment selection.

METHOD

In our present study, we have obtained blood samples from both patients with pulmonary arterial hypertension (PAH) and healthy individuals. We conducted a comparative transcriptome analysis to identify genes that are either upregulated or downregulated in PAH patients when compared to the control group. Subsequently, we carried out a validation study focusing on the log2-fold downregulated genes in PAH, employing Quantitative Real-Time PCR for confirmation. Additionally, we quantified the proteins encoded by the validated genes using the ELISA technique.

RESULTS

The results of the transcriptome analysis revealed that 97 genes were significantly upregulated, and 6 genes were significantly downregulated. Among these, we chose to focus on and validate only four of the downregulated genes, as they were directly or indirectly associated with the hypertension pathway. We also conducted validation studies for the proteins encoded by these genes, and the results were consistent with those obtained in the transcriptome analysis.

CONCLUSION

In conclusion, the findings of this study indicate that the four validated genes identified in the context of PAH can be further explored as potential targets for both diagnostic and therapeutic applications.

Extracellular purines in lung endothelial permeability and pulmonary diseases

The purinergic signaling system is an evolutionarily conserved and critical regulatory circuit that maintains homeostatic balance across various organ systems and cell types by providing compensatory responses to diverse pathologies. Despite cardiovascular diseases taking a leading position in human morbidity and mortality worldwide, pulmonary diseases represent significant health concerns as well. The endothelium of both pulmonary and systemic circulation (bronchial vessels) plays a pivotal role in maintaining lung tissue homeostasis by providing an active barrier and modulating adhesion and infiltration of inflammatory cells. However, investigations into purinergic regulation of lung endothelium have remained limited, despite widespread recognition of the role of extracellular nucleotides and adenosine in hypoxic, inflammatory, and immune responses within the pulmonary microenvironment. In this review, we provide an overview of the basic aspects of purinergic signaling in vascular endothelium and highlight recent studies focusing on pulmonary microvascular endothelial cells and endothelial cells from the pulmonary artery vasa vasorum. Through this compilation of research findings, we aim to shed light on the emerging insights into the purinergic modulation of pulmonary endothelial function and its implications for lung health and disease.

Hemodynamic and Clinical Response to Liver Transplantation in Children and Young Adults POPH Patients

Portopulmonary hypertension is an intractable form of pulmonary hypertension. Although liver transplantation is recommended for patients who respond poorly to treatments, the mechanisms by which liver transplantation improves pulmonary hypertension remain unclear. The present study investigated these mechanisms by retrospectively evaluating patients' data. This study retrospectively evaluated echocardiography and catheterization data before and after liver transplantation in 12 patients who underwent liver transplantation from 2001 to 2019. The 12 patients included one male and 11 females, of median age at liver transplantation of 10 years, 2 months. Nine patients underwent liver transplantation for congenital biliary atresia and three for portal vein aplasia or hypoplasia. Mean pulmonary arterial pressure was 44.1 ± 8.1 mmHg at the first cardiac catheter examination, 35.3 ± 7.8 mmHg before liver transplantation, and 29.5 ± 9.3 mmHg 6 months after liver transplantation. Pulmonary artery pressure was reduced by treatments of pulmonary hypertension and by liver transplantation. Pulmonary vascular resistance did not differ before and after liver transplantation, whereas the cardiac index decreased significantly, indicating that the significant reduction in mean pulmonary artery pressure was due to a decrease in cardiac index. Decreased cardiac index was thought to result from improvements in hyperdynamic conditions due to increased (normalized) systemic vascular resistance. Liver transplantation likely suppresses shear stress on pulmonary arteries, preventing further damage by hyper-circulation. A longer-term evaluation is required to determine the effect of improving pulmonary artery remodeling.

Unilateral Lung Removal in Combination with Monocrotaline or SU5416 in Rodents: A Reliable Model to Mimic the Pathology of the Human Pulmonary Hypertension

Pulmonary hypertension (PH) is a chronic and progressive disorder characterized by elevated mean pulmonary arterial pressure, pulmonary vascular remodeling, and the development of concentric laminar intimal fibrosis with plexiform lesions. While rodent models have been developed to study PH, they have certain deficiencies and do not entirely replicate the human disease due to the heterogeneity of PH pathology. Therefore, combined models are necessary to study PH. Recent studies have shown that altered pulmonary blood flow is a significant trigger in the development of vascular remodeling and neointimal lesions. One of the most promising rodent models for increased pulmonary flow is the combination of unilateral left pneumonectomy with a "second hit" of monocrotaline (MCT) or SU5416. The removal of one lung in this model forces blood to circulate only in the other lung and induces increased and turbulent pulmonary blood flow. This increased vascular flow leads to progressive remodeling and occlusion of small pulmonary arteries. The second hit by MCT or SU5416 leads to endothelial cell dysfunction, resulting in severe PH and the development of plexiform arteriopathy.

Clonal Expansion in Cardiovascular Pathology

Clonal expansion refers to the proliferation and selection of advantageous "clones" that are better suited for survival in a Darwinian manner. In recent years, we have greatly enhanced our understanding of cell clonality in the cardiovascular context. However, our knowledge of the underlying mechanisms behind this clonal selection is still severely limited. There is a transpiring pattern of clonal expansion of smooth muscle cells and endothelial cells-and, in some cases, macrophages-in numerous cardiovascular diseases irrespective of their differing microenvironments. These findings indirectly suggest the possible existence of stem-like vascular cells which are primed to respond during disease. Subsequent clones may undergo further phenotypic changes to adopt either protective or detrimental roles. By investigating these clone-forming vascular cells, we may be able to harness this inherent clonal nature for future therapeutic intervention. This review comprehensively discusses what is currently known about clonal expansion across the cardiovascular field. Comparisons of the clonal nature of vascular cells in atherosclerosis (including clonal hematopoiesis of indeterminate potential), pulmonary hypertension, aneurysm, blood vessel injury, ischemia- and tumor-induced angiogenesis, and cerebral cavernous malformations are evaluated. Finally, we discuss the potential clinical implications of these findings and propose that proper understanding and specific targeting of these clonal cells may provide unique therapeutic options for the treatment of these cardiovascular conditions.

PGC-1α-mediated angiogenesis prevents pulmonary hypertension in mice

Pulmonary hypertension (PH) is a life-threatening disease characterized by a progressive narrowing of pulmonary arterioles. Although VEGF is highly expressed in lung of patients with PH and in animal PH models, the involvement of angiogenesis remains elusive. To clarify the pathophysiological function of angiogenesis in PH, we compared the angiogenic response in hypoxia (Hx) and SU5416 (a VEGFR2 inhibitor) plus Hx (SuHx) mouse PH models using 3D imaging. The 3D imaging analysis revealed an angiogenic response in the lung of the Hx-PH, but not of the severer SuHx-PH model. Selective VEGFR2 inhibition with cabozantinib plus Hx in mice also suppressed angiogenic response and exacerbated Hx-PH to the same extent as SuHx. Expression of endothelial proliferator-activated receptor γ coactivator 1α (PGC-1α) increased along with angiogenesis in lung of Hx-PH but not SuHx mice. In pulmonary endothelial cell-specific Ppargc1a-KO mice, the Hx-induced angiogenesis was suppressed, and PH was exacerbated along with increased oxidative stress, cellular senescence, and DNA damage. By contrast, treatment with baicalin, a flavonoid enhancing PGC-1α activity in endothelial cells, ameliorated Hx-PH with increased Vegfa expression and angiogenesis. Pulmonary endothelial PGC-1α-mediated angiogenesis is essential for adaptive responses to Hx and might represent a potential therapeutic target for PH.

Prostacyclin mimetics inhibit DRP1-mediated pro-proliferative mitochondrial fragmentation in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare cardiopulmonary disorder, involving the remodelling of the small pulmonary arteries. Underlying this remodelling is the hyper-proliferation of pulmonary arterial smooth muscle cells within the medial layers of these arteries and their encroachment on the lumen. Previous studies have demonstrated an association between excessive mitochondrial fragmentation, a consequence of increased expression and post-translational activation of the mitochondrial fission protein dynamin-related protein 1 (DRP1), and pathological proliferation in PASMCs derived from PAH patients. However, the impact of prostacyclin mimetics, widely used in the treatment of PAH, on this pathological mitochondrial fragmentation remains unexplored. We hypothesise that these agents, which are known to attenuate the proliferative phenotype of PAH PASMCs, do so in part by inhibiting mitochondrial fragmentation. In this study, we confirmed the previously reported increase in DRP1-mediated mitochondrial hyper-fragmentation in PAH PASMCs. We then showed that the prostacyclin mimetic treprostinil signals via either the Gs-coupled IP or EP2 receptor to inhibit mitochondrial fragmentation and the associated hyper-proliferation in a manner analogous to the DRP1 inhibitor Mdivi-1. We also showed that treprostinil recruits either the IP or EP2 receptor to activate PKA and induce the phosphorylation of DRP1 at the inhibitory residue S637 and inhibit that at the stimulatory residue S616, both of which are suggestive of reduced DRP1 fission activity. Like treprostinil, MRE-269, an IP receptor agonist, and butaprost, an EP2 receptor agonist, attenuated DRP1-mediated mitochondrial fragmentation through PKA. We conclude that prostacyclin mimetics produce their anti-proliferative effects on PAH PASMCs in part by inhibiting DRP1-mediated mitochondrial fragmentation.

Pathophysiology and pathogenic mechanisms of pulmonary hypertension: role of membrane receptors, ion channels, and Ca2+ signaling

The pulmonary circulation is a low-resistance, low-pressure, and high-compliance system that allows the lungs to receive the entire cardiac output. Pulmonary arterial pressure is a function of cardiac output and pulmonary vascular resistance, and pulmonary vascular resistance is inversely proportional to the fourth power of the intraluminal radius of the pulmonary artery. Therefore, a very small decrease of the pulmonary vascular lumen diameter results in a significant increase in pulmonary vascular resistance and pulmonary arterial pressure. Pulmonary arterial hypertension is a fatal and progressive disease with poor prognosis. Regardless of the initial pathogenic triggers, sustained pulmonary vasoconstriction, concentric vascular remodeling, occlusive intimal lesions, in situ thrombosis, and vascular wall stiffening are the major and direct causes for elevated pulmonary vascular resistance in patients with pulmonary arterial hypertension and other forms of precapillary pulmonary hypertension. In this review, we aim to discuss the basic principles and physiological mechanisms involved in the regulation of lung vascular hemodynamics and pulmonary vascular function, the changes in the pulmonary vasculature that contribute to the increased vascular resistance and arterial pressure, and the pathogenic mechanisms involved in the development and progression of pulmonary hypertension. We focus on reviewing the pathogenic roles of membrane receptors, ion channels, and intracellular Ca2+ signaling in pulmonary vascular smooth muscle cells in the development and progression of pulmonary hypertension.

Effects of the Oral Angiotensin II Type 2 Receptor Agonist C21 in Sugen-Hypoxia Induced Pulmonary Hypertension in Rats

Substantial evidence supports the involvement of the renin-angiotensin system in pulmonary hypertension (PH), and the angiotensin II type 2 receptor (AT2R) is known to exert tissue protective actions. The effect of the selective AT2R agonist C21 (also known as Compound 21 or buloxibutid) was evaluated in the rat Sugen-hypoxia PH model. After a single injection of Sugen 5416 and hypoxia for 21 days, C21 (2 or 20 mg/kg) or vehicle was administered perorally twice daily from Day 21 to Day 55. On Day 56, hemodynamic assessments were performed, and lung and heart tissue were prepared for quantification of cardiac and vascular remodeling and fibrosis. Treatment with C21 20 mg/kg improved cardiac output and stroke volume and decreased right ventricular hypertrophy (all p < 0.05). Treatment with C21 2 mg/kg significantly decreased vessel wall and muscular layer thickness and increased the luminal opening in vessels >100 μm (all p < 0.05). There were no significant differences between the two C21 doses on any parameter, and post hoc analyses comparing the merged C21 groups with the vehicle group showed that C21 treatment reduced vascular remodeling (reduced endothelial proliferation and thickening of the vascular wall) in vessels of all sizes; moreover, the diastolic pulmonary artery pressure and right ventricular pressure were reduced along with reduction of right ventricular hypertrophy. Sugen 5416 and hypoxia increased pulmonary collagen deposition, which was counteracted by C21 20 mg/kg. In conclusion, the effects of C21 on vascular remodeling, hemodynamic alterations, and fibrosis suggest that AT2R agonists may have a role in Group 1 and 3 PH treatment.

Tensions in Taxonomies: Current Understanding and Future Directions in the Pathobiologic Basis and Treatment of Group 1 and Group 3 Pulmonary Hypertension

In the over 100 years since the recognition of pulmonary hypertension (PH), immense progress and significant achievements have been made with regard to understanding the pathophysiology of the disease and its treatment. These advances have been mostly in idiopathic pulmonary arterial hypertension (IPAH), which was classified as Group 1 Pulmonary Hypertension (PH) at the Second World Symposia on PH in 1998. However, the pathobiology of PH due to chronic lung disease, classified as Group 3 PH, remains poorly understood and its treatments thus remain limited. We review the history of the classification of the five groups of PH and aim to provide a state-of-the-art review of the understanding of the pathogenesis of Group 1 PH and Group 3 PH including insights gained from novel high-throughput omics technologies that have revealed heterogeneities within these categories as well as similarities between them. Leveraging the substantial gains made in understanding the genomics, epigenomics, proteomics, and metabolomics of PAH to understand the full spectrum of the complex, heterogeneous disease of PH is needed. Multimodal omics data as well as supervised and unbiased machine learning approaches after careful consideration of the powerful advantages as well as of the limitations and pitfalls of these technologies could lead to earlier diagnosis, more precise risk stratification, better predictions of disease response, new sub-phenotype groupings within types of PH, and identification of shared pathways between PAH and other types of PH that could lead to new treatment targets. © 2023 American Physiological Society. Compr Physiol 13:4295-4319, 2023.

Important Role of Endogenous Nerve Growth Factor Receptor in the Pathogenesis of Hypoxia-Induced Pulmonary Hypertension in Mice

Pulmonary arterial hypertension (PAH) remains a disease with poor prognosis; thus, a new mechanism for PAH treatment is necessary. Circulating nerve growth factor receptor (Ngfr)-positive cells in peripheral blood mononuclear cells are associated with disease severity and the prognosis of PAH patients; however, the role of Ngfr in PAH is unknown. In this study, we evaluated the function of Ngfr using Ngfr gene-deletion (Ngfr-/-) mice. To elucidate the role of Ngfr in pulmonary hypertension (PH), we used Ngfr-/- mice that were exposed to chronic hypoxic conditions (10% O2) for 3 weeks. The development of hypoxia-induced PH was accelerated in Ngfr-/- mice compared to littermate controls. In contrast, the reconstitution of bone marrow (BM) in Ngfr-/- mice transplanted with wild-type BM cells improved PH. Notably, the exacerbation of PH in Ngfr-/- mice was accompanied by the upregulation of pulmonary vascular remodeling-related genes in lung tissue. In a hypoxia-induced PH model, Ngfr gene deletion resulted in PH exacerbation. This suggests that Ngfr may be a key molecule involved in the pathogenesis of PAH.

The Evolving Management and Treatment Options for Patients with Pulmonary Hypertension: Current Evidence and Challenges

Pulmonary hypertension may develop as a disease process specific to pulmonary arteries with no identifiable cause or may occur in relation to other cardiopulmonary and systemic illnesses. The World Health Organization (WHO) classifies pulmonary hypertensive diseases on the basis of primary mechanisms causing increased pulmonary vascular resistance. Effective management of pulmonary hypertension begins with accurately diagnosing and classifying the disease in order to determine appropriate treatment. Pulmonary arterial hypertension (PAH) is a particularly challenging form of pulmonary hypertension as it involves a progressive, hyperproliferative arterial process that leads to right heart failure and death if untreated. Over the last two decades, our understanding of the pathobiology and genetics behind PAH has evolved and led to the development of several targeted disease modifiers that ameliorate hemodynamics and quality of life. Effective risk management strategies and more aggressive treatment protocols have also allowed better outcomes for patients with PAH. For those patients who experience progressive PAH with medical therapy, lung transplantation remains a life-saving option. More recent work has been directed at developing effective treatment strategies for other forms of pulmonary hypertension, such as chronic thromboembolic pulmonary hypertension (CTEPH) and pulmonary hypertension due to other lung or heart diseases. The discovery of new disease pathways and modifiers affecting the pulmonary circulation is an ongoing area of intense investigation.

Identification of immune-related hub genes and analysis of infiltrated immune cells of idiopathic pulmonary artery hypertension

Objectives

Idiopathic pulmonary artery hypertension (IPAH) is a rare but life-threaten disease. However, the mechanism underlying IPAH is unclear. In this study, underlying mechanism, infiltration of immune cells, and immune-related hub genes of IPAH were analyzed via bioinformatics.

Methods

GSE15197, GSE48149, GSE113439, and GSE117261 were merged as lung dataset. Weighted gene correlation network analysis (WGCNA) was used to construct the co-expression gene networks of IPAH. Gene Ontology and pathway enrichment analysis were performed using DAVID, gene set enrichment analysis (GSEA), and gene set variation analysis (GSVA). Infiltration of immune cells in lung samples was analyzed using CIBERSORT. GSE22356 and GSE33463 were merged as peripheral blood mononuclear cells (PBMCs) dataset. Immune-related differentially expressed genes (IRDEGs) of lung and PBMCs dataset were analyzed. Based on the intersection between two sets of IRDEGs, hub genes were screened using machine learning algorithms and validated by RT-qPCR. Finally, competing endogenous RNA (ceRNA) networks of hub genes were constructed.

Results

The gray module was the most relevant module and genes in the module enriched in terms like inflammatory and immune responses. The results of GSEA and GSVA indicated that increasement in cytosolic calcium ion, and metabolism dysregulation play important roles in IPAH. The proportions of T cells CD4 memory resting and macrophage M1 were significantly greater in IPAH group, while the proportions of monocytes and neutrophils were significantly lower in IPAH group. IRDEGs of two datasets were analyzed and the intersection between two set of IRDEGs were identified as candidate hub genes. Predictive models for IPAH were constructed using data from PBMCs dataset with candidate hub genes as potential features via LASSO regression and XGBoost algorithm, respectively. CXCL10 and VIPR1 were identified as hub genes and ceRNA networks of CXCL10 was constructed.

Conclusion

Inflammatory response, increasement in cytosolic calcium ion, and metabolism dysregulation play important roles in IPAH. T cells CD4 memory resting and macrophage M1 were significantly infiltrated in lung samples from patients with IPAH. IRDEGs of lung dataset and PBMCs dataset were analyzed, and CXCL10 and VIPR1 were identified as hub genes.

Characterization of pulmonary vascular remodeling and MicroRNA-126-targets in COPD-pulmonary hypertension

BACKGROUND

Despite causing increased morbidity and mortality, pulmonary hypertension (PH) in chronic obstructive pulmonary disease (COPD) patients (COPD-PH) lacks treatment, due to incomplete understanding of its pathogenesis. Hypertrophy of pulmonary arterial walls and pruning of the microvasculature with loss of capillary beds are known features of pulmonary vascular remodeling in COPD. The remodeling features of pulmonary medium- and smaller vessels in COPD-PH lungs are less well described and may be linked to maladaptation of endothelial cells to chronic cigarette smoking (CS). MicroRNA-126 (miR126), a master regulator of endothelial cell fate, has divergent functions that are vessel-size specific, supporting the survival of large vessel endothelial cells and inhibiting the proliferation of microvascular endothelial cells. Since CS decreases miR126 in microvascular lung endothelial cells, we set out to characterize the remodeling by pulmonary vascular size in COPD-PH and its relationship with miR126 in COPD and COPD-PH lungs.

METHODS

Deidentified lung tissue was obtained from individuals with COPD with and without PH and from non-diseased non-smokers and smokers. Pulmonary artery remodeling was assessed by ⍺-smooth muscle actin (SMA) abundance via immunohistochemistry and analyzed by pulmonary artery size. miR126 and miR126-target abundance were quantified by qPCR. The expression levels of ceramide, ADAM9, and endothelial cell marker CD31 were assessed by immunofluorescence.

RESULTS

Pulmonary arteries from COPD and COPD-PH lungs had significantly increased SMA abundance compared to non-COPD lungs, especially in small pulmonary arteries and the lung microvasculature. This was accompanied by significantly fewer endothelial cell markers and increased pro-apoptotic ceramide abundance. miR126 expression was significantly decreased in lungs of COPD individuals. Of the targets tested (SPRED1, VEGF, LAT1, ADAM9), lung miR126 most significantly inversely correlated with ADAM9 expression. Compared to controls, ADAM9 was significantly increased in COPD and COPD-PH lungs, predominantly in small pulmonary arteries and lung microvasculature.

CONCLUSION

Both COPD and COPD-PH lungs exhibited significant remodeling of the pulmonary vascular bed of small and microvascular size, suggesting these changes may occur before or independent of the clinical development of PH. Decreased miR126 expression with reciprocal increase in ADAM9 may regulate endothelial cell survival and vascular remodeling in small pulmonary arteries and lung microvasculature in COPD and COPD-PH.

Deletion of classical transient receptor potential 1, 3 and 6 alters pulmonary vasoconstriction in chronic hypoxia-induced pulmonary hypertension in mice

Chronic hypoxia-induced pulmonary hypertension (CHPH) is a severe disease that is characterized by increased proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs) leading to pulmonary vascular remodeling. The resulting increase in pulmonary vascular resistance (PVR) causes right ventricular hypertrophy and ultimately right heart failure. In addition, increased PVR can also be a consequence of hypoxic pulmonary vasoconstriction (HPV) under generalized hypoxia. Increased proliferation and migration of PASMCs are often associated with high intracellular Ca²⁺ concentration. Recent publications suggest that Ca²⁺-permeable nonselective classical transient receptor potential (TRPC) proteins-especially TRPC1 and 6-are crucially involved in acute and sustained hypoxic responses and the pathogenesis of CHPH. The aim of our study was to investigate whether the simultaneous deletion of TRPC proteins 1, 3 and 6 protects against CHPH-development and affects HPV in mice. We used a mouse model of chronic hypoxia as well as isolated, ventilated and perfused mouse lungs and PASMC cell cultures. Although right ventricular systolic pressure as well as echocardiographically assessed PVR and right ventricular wall thickness (RVWT) were lower in TRPC1, 3, 6-deficient mice, these changes were not related to a decreased degree of pulmonary vascular muscularization and a reduced proliferation of PASMCs. However, both acute and sustained HPV were almost absent in the TRPC1, 3, 6-deficient mice and their vasoconstrictor response upon KCl application was reduced. This was further validated by myographical experiments. Our data revealed that 1) TRPC1, 3, 6-deficient mice are partially protected against development of CHPH, 2) these changes may be caused by diminished HPV and not an altered pulmonary vascular remodeling.

Microrna-486-5P Regulates Human Pulmonary Artery Smooth Muscle Cell Migration via Endothelin-1

Pulmonary arterial hypertension (PAH) is a fatal or life-threatening disorder characterized by elevated pulmonary arterial pressure and pulmonary vascular resistance. Abnormal vascular remodeling, including the proliferation and phenotypic modulation of pulmonary artery smooth muscle cells (PASMCs), represents the most critical pathological change during PAH development. Previous studies showed that miR-486 could reduce apoptosis in different cells; however, the role of miR-486 in PAH development or HPASMC proliferation and migration remains unclear. After 6 h of hypoxia treatment, miR-486-5p was significantly upregulated in HPASMCs. We found that miR-486-5p could upregulate the expression and secretion of ET-1. Furthermore, transfection with a miR-486-5p mimic could induce HPASMC proliferation and migration. We also found that miRNA-486-5p could downregulate the expression of SMAD2 and the phosphorylation of SMAD3. According to previous studies, the loss of SMAD3 may play an important role in miRNA-486-5p-induced HPASMC proliferation. Although the role of miRNA-486-5p in PAH in in vivo models still requires further investigation and confirmation, our findings show the potential roles and effects of miR-486-5p during PAH development.

Imaging in Pulmonary Vascular Disease-Understanding Right Ventricle-Pulmonary Artery Coupling

The right ventricle (RV) and pulmonary arterial (PA) tree are inextricably linked, continually transferring energy back and forth in a process known as RV-PA coupling. Healthy organisms maintain this relationship in optimal balance by modulating RV contractility, pulmonary vascular resistance, and compliance to sustain RV-PA coupling through life's many physiologic challenges. Early in states of adaptation to cardiovascular disease-for example, in diastolic heart failure-RV-PA coupling is maintained via a multitude of cellular and mechanical transformations. However, with disease progression, these compensatory mechanisms fail and become maladaptive, leading to the often-fatal state of "uncoupling." Noninvasive imaging modalities, including echocardiography, magnetic resonance imaging, and computed tomography, allow us deeper insight into the state of coupling for an individual patient, providing for prognostication and potential intervention before uncoupling occurs. In this review, we discuss the physiologic foundations of RV-PA coupling, elaborate on the imaging techniques to qualify and quantify it, and correlate these fundamental principles with clinical scenarios in health and disease. © 2022 American Physiological Society. Compr Physiol 12: 1-26, 2022.

Radiation-induced cardiac side-effects: The lung as target for interacting damage and intervention

Radiotherapy is part of the treatment for many thoracic cancers. During this treatment heart and lung tissue can often receive considerable doses of radiation. Doses to the heart can potentially lead to cardiac effects such as pericarditis and myocardial fibrosis. Common side effects after lung irradiation are pneumonitis and pulmonary fibrosis. It has also been shown that lung irradiation has effects on cardiac function. In a rat model lung irradiation caused remodeling of the pulmonary vasculature increasing resistance of the pulmonary vascular bed, leading to enhanced pulmonary artery pressure, right ventricle hypertrophy and reduced right ventricle performance. Even more pronounced effects are observed when both, lung and heart are irradiated.

The effects observed after lung irradiation show striking similarities with symptoms of pulmonary arterial hypertension. In particular, the vascular remodeling in lung tissue seems to have similar underlying features. Here, we discuss the similarities and differences of vascular remodeling observed after thoracic irradiation compared to those in pulmonary arterial hypertension patients and research models. We will also assess how this knowledge of similarities could potentially be translated into interventions which would be beneficial for patients treated for thoracic tumors, where dose to lung tissue is often unavoidable.

Polydatin Glycosides Improve Monocrotaline-Induced Pulmonary Hypertension Injury by Inhibiting Endothelial-To-Mesenchymal Transition

Objective: To study the effect of polydatin on the injury of pulmonary arterial hypertension (PAH) induced by monocrotaline (MCT).

Methods: SD rats were induced to develop PAH injury by a single subcutaneous injection of MCT (60 mg/kg). From the second day, rats in the administration group were orally given sildenafil (20 mg/kg) and polydatin (30 or 60 mg/kg) for 3 weeks. At the end of the experiment, right ventricular hypertrophy (RVH) index of SD rats was calculated, pathological damage was assessed by HE staining, transcription levels of target genes were detected by RT-PCR and Elisa, and expression levels of Endothelial-to-mesenchymal transition (EndMT) related proteins were detected by immunohistochemistry (IHC) and immunofluorescence (IF). Finally, molecular docking analysis was used to verify the interaction of polydatin on the main targets.

Results: Polydatin could significantly restore the body function, reduce MCT-induced PAH injury, reduce serum biochemical indices; polydatin could effectively inhibit EndMT process by decreasing the expression of N-cadherin, β-catenin and vimentin; polydatin could down-regulate TAGLN expression and increase PECAM1 expression to reduce pulmonary vascular remodeling. The interaction between polydatin and EndMT target was confirmed by molecular docking operation.

Conclusion: Pharmacological experiments combined with Combining molecular docking was first used to clarify that polydatin can reduce the pulmonary endothelial dysfunction and pulmonary vascular remodeling induced by MCT by inhibiting EndMT. The results of the study provide new ideas for the further treatment of PAH injury.

Vascular Remodeling in Pulmonary Arterial Hypertension: The Potential Involvement of Innate and Adaptive Immunity

Pulmonary arterial hypertension (PAH) is a severe disease with high morbidity and mortality. Current therapies are mainly focused on vasodilative agents to improve prognosis. However, recent literature has shown the important interaction between immune cells and stromal vascular cells in the pathogenic modifications of the pulmonary vasculature. The immunological pathogenesis of PAH is known as a complex interplay between immune cells and vascular stromal cells, via direct contacts and/or their production of extra-cellular/diffusible factors such as cytokines, chemokines, and growth factors. These include, the B-cell—mast-cell axis, endothelium mediated fibroblast activation and subsequent M2 macrophage polarization, anti-endothelial cell antibodies and the versatile role of IL-6 on vascular cells. This review aims to outline the major pathophysiological changes in vascular cells caused by immunological mechanisms, leading to vascular remodeling, increased pulmonary vascular resistance and eventually PAH. Considering the underlying immunological mechanisms, these mechanisms may be key to halt progression of disease.

Lung transplant to manage end-stage lung disease due to idiopathic pulmonary hemosiderosis: A review of the literature

Idiopathic pulmonary hemosiderosis (IPH) is a rare immunological disease with a genetic predisposition. It is characterized by recurrent episodes of diffuse alveolar hemorrhage (DAH). Timely use of immunosuppressive medications has significantly improved overall outcomes, including mortality. Still, uncontrolled and frequent episodes of DAH can eventually cause pulmonary fibrosis, leading to end-stage lung disease (ESLD). The objective of the present project was to scrutinize the literature and summarize the demographic, clinical, radiological, and histopathological features, as well as the overall outcomes, in this patient population following lung transplant. The Medline database was searched using the PubMed platform. Articles published in English between 1960 and 2020 were included in the search. Different search terms were used to identify all patients who underwent lung transplantation to manage ESLD due to IPH. Only four cases of lung transplantation have been reported in the literature in patients with IPH. All but one of these underwent deceased donor lung transplant; recurrence was reported in two of these patients and suspected in the third. One patient received living donor lung transplant and had no recurrence during a five-year follow-up. Patients with IPH should not be excluded from lung transplantation because the disease may not recur in all patients, and even when it does recur it can be promptly treated by increasing immunosuppression.

Pulmonary Arterial Hypertension: Emerging Principles of Precision Medicine across Basic Science to Clinical Practice

Pulmonary arterial hypertension (PAH) is an enigmatic and deadly vascular disease with no known cure. Recent years have seen rapid advances in our understanding of the molecular underpinnings of PAH, with an expanding knowledge of the molecular, cellular, and systems-level drivers of disease that are being translated into novel therapeutic modalities. Simultaneous advances in clinical technology have led to a growing list of tools with potential application to diagnosis and phenotyping. Guided by fundamental biology, these developments hold the potential to usher in a new era of personalized medicine in PAH with broad implications for patient management and great promise for improved outcomes.

Bronchiectasis: Retrospective Analysis of Clinical and Pathological Findings in a Tertiary-Care Hospital

BACKGROUND

Bronchiectasis is still a challenging chronic lung disease in developing countries. Patients with bronchiectasis can also have pulmonary hypertension. There are sparse data on the prevalence of pulmonary hypertension in patients with bronchiectasis. Materials and methods. Archived H&E-stained slides of 141 patients histopathologically diagnosed with bronchiectasis were reevaluated. Cases were categorized into 4 subgroups based on histology: tubular, varicose, follicular, and cystic. In addition, concomitant histopathological changes were also reevaluated. For patients with available CT sections, main, right, and left pulmonary artery (PA) diameters and PA/aorta ratio were measured with regard to pulmonary hypertension.

RESULTS

Of the cases, 70% (n = 89) were female and 30% (n = 52) were male, with a mean age of 36.58 in females and 33.84 in males. Histopathologically, 43% (n = 68) of the cases showed follicular, 37% (n = 59) showed varicose, 35% (n = 56) showed tubular, and 28% (n = 45) showed cystic bronchiectasis morphology. All cases showed chronic inflammation, fibrosis, muscle destruction, and cartilage destruction. Aspergillus were present in 11% of the cases showing cystic morphology. Approximately 17% of the cases (n = 24) were found to have neuroendocrine cell proliferations. In cases with medial hypertrophy, a statistically significant increase in the left pulmonary artery diameter was radiologically determined.

CONCLUSIONS

Medial hypertrophy was found to be significant with regard to indicating a radiological increase in left pulmonary artery diameter. Vascular changes observed in bronchiectasis cases and the presence of neuroendocrine cell proliferations should be specified in pathology reports, and aspergilloma should be carefully investigated in cases with predominant cystic morphology.

Therapy for Pulmonary Arterial Hypertension: Glance on Nitric Oxide Pathway

Pulmonary arterial hypertension (PAH) is a severe disease with a resultant increase of the mean pulmonary arterial pressure, right ventricular hypertrophy and eventual death. Research in recent years has produced various therapeutic options for its clinical management but the high mortality even under treatment remains a big challenge attributed to the complex pathophysiology. Studies from clinical and non-clinical experiments have revealed that the nitric oxide (NO) pathway is one of the key pathways underlying the pathophysiology of PAH. Many of the essential drugs used in the management of PAH act on this pathway highlighting its significant role in PAH. Meanwhile, several novel compounds targeting on NO pathway exhibits great potential to become future therapy medications. Furthermore, the NO pathway is found to interact with other crucial pathways. Understanding such interactions could be helpful in the discovery of new drug that provide better clinical outcomes.

Clonal hematopoiesis with JAK2V617F promotes pulmonary hypertension with ALK1 upregulation in lung neutrophils

Pulmonary hypertension (PH) is a progressive cardiopulmonary disease characterized by pulmonary arterial remodeling. Clonal somatic mutations including JAK2V617F, the most frequent driver mutation among myeloproliferative neoplasms, have recently been identified in healthy individuals without hematological disorders. Here, we reveal that clonal hematopoiesis with JAK2V617F exacerbates PH and pulmonary arterial remodeling in mice. JAK2V617F-expressing neutrophils specifically accumulate in pulmonary arterial regions, accompanied by increases in neutrophil-derived elastase activity and chemokines in chronic hypoxia-exposed JAK2V617F transgenic (JAK2^V617F) mice, as well as recipient mice transplanted with JAK2^V617F bone marrow cells. JAK2V617F progressively upregulates Acvrl1 (encoding ALK1) during the differentiation from bone marrow stem/progenitor cells peripherally into mature neutrophils of pulmonary arterial regions. JAK2V617F-mediated STAT3 phosphorylation upregulates ALK1-Smad1/5/8 signaling. ALK1/2 inhibition completely prevents the development of PH in JAK2^V617F mice. Finally, our prospective clinical study identified JAK2V617F-positive clonal hematopoiesis is more common in PH patients than in healthy subjects. These findings indicate that clonal hematopoiesis with JAK2V617F causally leads to PH development associated with ALK1 upregulation.

Vascular remodeling of the small pulmonary arteries and measures of vascular pruning on computed tomography

Pulmonary hypertension is characterized histologically by intimal and medial thickening in the small pulmonary arteries, eventually resulting in vascular "pruning." Computed tomography (CT)-based quantification of pruning is associated with clinical measures of pulmonary hypertension, but it is not established whether CT-based pruning correlates with histologic arterial remodeling. Our sample consisted of 138 patients who underwent resection for early-stage lung adenocarcinoma. From histologic sections, we identified small pulmonary arteries and measured the relative area comprising the intima and media (VWA%), with higher VWA% representing greater histologic remodeling. From pre-operative CTs, we used image analysis algorithms to calculate the small vessel volume fraction (BV5/TBV) as a CT-based indicator of pruning (lower BV5/TBV represents greater pruning). We investigated relationships of CT pruning and histologic remodeling using Pearson correlation, simple linear regression, and multivariable regression with adjustment for age, sex, height, weight, smoking status, and total pack-years. We also tested for effect modification by sex and smoking status. In primary models, more severe CT pruning was associated with greater histologic remodeling. The Pearson correlation coefficient between BV5/TBV and VWA% was -0.41, and in linear regression models, VWA% was 3.13% higher (95% CI: 1.95-4.31%, p < 0.0001) per standard deviation lower BV5/TBV. This association persisted after multivariable adjustment. We found no evidence that these relationships differed by sex or smoking status. Among individuals who underwent resection for lung adenocarcinoma, more severe CT-based vascular pruning was associated with greater histologic arterial remodeling. These findings suggest CT imaging may be a non-invasive indicator of pulmonary vascular pathology.

Evidence for Multiple Origins of De Novo Formed Vascular Smooth Muscle Cells in Pulmonary Hypertension: Challenging the Dominant Model of Pre-Existing Smooth Muscle Expansion

Vascular remodeling is a prominent feature of pulmonary hypertension. This process involves increased muscularization of already muscularized vessels as well as neo-muscularization of non-muscularized vessels. The cell-of-origin of the newly formed vascular smooth muscle cells has been a subject of intense debate in recent years. Identifying these cells may have important clinical implications since it opens the door for attempts to therapeutically target the progenitor cells and/or reverse the differentiation of their progeny. In this context, the dominant model is that these cells derive from pre-existing smooth muscle cells that are activated in response to injury. In this mini review, we present the evidence that is in favor of this model and, at the same time, highlight other studies indicating that there are alternative cellular sources of vascular smooth muscle cells in pulmonary vascular remodeling.

miR-204: Molecular Regulation and Role in Cardiovascular and Renal Diseases

The field of microRNA research has evolved from studies aiming to gauge the importance of microRNAs to those focusing on understanding a subset of specific microRNAs that have emerged as potent regulators of molecular systems and pathophysiological conditions. In this article, we review the molecular features and regulation of miR-204 and the growing body of evidence for an important role of miR-204 in the regulation of cardiovascular and renal physiology and pathophysiological processes. miR-204 exhibits a highly tissue-specific expression pattern, and miR-204 abundance is regulated by several transcriptional and posttranscriptional mechanisms. Strong evidence supports a role for miR-204 in attenuating pulmonary arterial hypertension and hypertensive and diabetic renal injury while promoting hypertension and endothelial dysfunction in a wide range of model systems. miR-204 may influence these disease processes by targeting several biological pathways in a tissue-specific manner. miR-204 is dysregulated in patients with cardiovascular and renal diseases. The unequivocal functional roles and clear clinical relevance indicate that miR-204 is a high-value microRNA in cardiovascular and renal diseases.

Histopathological changes of pulmonary vascular remodeling in dogs affected with pulmonary hypertension secondary to degenerative mitral valve disease

INTRODUCTION/OBJECTIVES

Pulmonary hypertension (PH) can cause pulmonary arterial remodeling. Medial remodeling is a structural change of the pulmonary artery seen with PH. Hyperplasia and hypertrophy of pulmonary arterial smooth muscle cells (SMCs) are suggested as causes of medial remodeling. To demonstrate the histopathological changes of the pulmonary artery in dogs affected with PH secondary to degenerative mitral valve disease (DMVD) compared with DMVD without PH and control dogs.

ANIMALS

Lung samples obtained from the carcasses of 19 older small-breed dogs (Control, n = 5; DMVD, n = 7; DMVD + PH, n = 7).

MATERIALS AND METHODS

Lung tissue sections were stained with hematoxylin and eosin, Masson's trichrome, and proliferating cell nuclear antigen (PCNA) immunohistochemistry.

RESULTS

The internal diameters of the pulmonary artery in the three groups were not different. Masson's trichrome staining revealed no collagen deposition in the intimal layer of the pulmonary artery in all dogs. The external diameter, percentage of medial thickness (%MT), percentage of SMC layer and collagen deposition areas, average number of SMCs, and the percentage of PCNA positive cells (%PCNA) of the pulmonary artery were increased in the DMVD and DMVD + PH groups compared with the control group. The %PCNA in the DMVD + PH group was significantly decreased when compared with the DMVD group.

CONCLUSIONS

Medial remodeling was found in left-sided heart failure DMVD dogs with and without PH. The medial remodeling in DMVD dogs with and without PH is related to SMC hyperplasia, hypertrophy, and collagen deposition, leading to an increased medial layer thickness of the pulmonary artery.

AMPK and Pulmonary Hypertension: Crossroads Between Vasoconstriction and Vascular Remodeling

Pulmonary hypertension (PH) is a debilitating and life-threatening disease characterized by increased blood pressure within the pulmonary arteries. Adenosine monophosphate-activated protein kinase (AMPK) is a heterotrimeric serine-threonine kinase that contributes to the regulation of metabolic and redox signaling pathways. It has key roles in the regulation of cell survival and proliferation. The role of AMPK in PH is controversial because both inhibition and activation of AMPK are preventive against PH development. Some clinical studies found that metformin, the first-line antidiabetic drug and the canonical AMPK activator, has therapeutic efficacy during treatment of early-stage PH. Other study findings suggest the use of metformin is preferentially beneficial for treatment of PH associated with heart failure with preserved ejection fraction (PH-HFpEF). In this review, we discuss the "AMPK paradox" and highlight the differential effects of AMPK on pulmonary vasoconstriction and pulmonary vascular remodeling. We also review the effects of AMPK activators and inhibitors on rescue of preexisting PH in animals and include a discussion of gender differences in the response to metformin in PH.

Up-Regulation of the Long Noncoding RNA X-Inactive-Specific Transcript and the Sex Bias in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a sex-biased disease. Increased expression and activity of the long-noncoding RNA X-inactive-specific transcript (Xist), essential for X-chromosome inactivation and dosage compensation of X-linked genes, may explain the sex bias of PAH. The present studies used a murine model of plexiform PAH, the intersectin-1s (ITSN) heterozygous knockout (KOITSN+/-) mouse transduced with an ITSN fragment (EHITSN) possessing endothelial cell proliferative activity, in conjunction with molecular, cell biology, biochemical, morphologic, and functional approaches. The data demonstrate significant sex-centered differences with regard to EHITSN-induced alterations in pulmonary artery remodeling, lung hemodynamics, and p38/ETS domain containing protein/c-Fos signaling, altogether leading to a more severe female lung PAH phenotype. Moreover, the long-noncoding RNA-Xist is up-regulated in the lungs of female EHITSN-KOITSN+/- mice compared with that in female wild-type mice, leading to sex-specific modulation of the X-linked gene ETS domain containing protein and its target, two molecular events also characteristic to female human PAH lung. More importantly, cyclin A1 expression in the S and G2/M phases of the cell cycle of synchronized pulmonary artery endothelial cells of female PAH patients is greater versus controls, suggesting functional hyperproliferation. Thus, Xist up-regulation leading to female pulmonary artery endothelial cell sexual dimorphic behavior may provide a better understanding of the origin of sex bias in PAH. Notably, the EHITSN-KOITSN+/- mouse is a unique experimental animal model of PAH that recapitulates most of the sexually dimorphic characteristics of human disease.

Sphingosine 1 Phosphate (S1P) Receptor 1 Is Decreased in Human Lung Microvascular Endothelial Cells of Smokers and Mediates S1P Effect on Autophagy

Destruction of alveoli by apoptosis induced by cigarette smoke (CS) is a major driver of emphysema pathogenesis. However, when compared to cells isolated from non-smokers, primary human lung microvascular endothelial cells (HLMVECs) isolated from chronic smokers are more resilient when exposed to apoptosis-inducing ceramide. Whether this adaptation restores homeostasis is unknown. To better understand the phenotype of HLMVEC in smokers, we interrogated a major pro-survival pathway supported by sphingosine-1-phosphate (S1P) signaling via S1P receptor 1 (S1P1). Primary HLMVECs from lungs of non-smoker or smoker donors were isolated and studied in culture for up to five passages. S1P1 mRNA and protein abundance were significantly decreased in HLMVECs from smokers compared to non-smokers. S1P1 was also decreased in situ in lungs of mice chronically exposed to CS. Levels of S1P1 expression tended to correlate with those of autophagy markers, and increasing S1P (via S1P lyase knockdown with siRNA) stimulated baseline macroautophagy with lysosomal degradation. In turn, loss of S1P1 (siRNA) inhibited these effects of S1P on HLMVECs autophagy. These findings suggest that the anti-apoptotic phenotype of HLMVECs from smokers may be maladaptive, since it is associated with decreased S1P1 expression that may impair their autophagic response to S1P.

Identifying Potential Mutations Responsible for Cases of Pulmonary Arterial Hypertension

Pulmonary Arterial Hypertension (PAH) is a progressive and devastating disease for which there is an escalating body of genetic and related pathophysiological information on disease pathobiology. Nevertheless, the success to date in identifying susceptibility genes, genetic variants and epigenetic processes has been limited due to PAH clinical multi-faceted variations. A number of germline gene candidates have been proposed but demonstrating consistently the association with PAH has been problematic, at least partly due to the reduced penetrance and variable expressivity. Although the data for bone morphogenetic protein receptor type 2 (BMPR2) and related genes remains undoubtedly the most extensive, recent advanced gene sequencing technologies have facilitated the discovery of further gene candidates with mutations among those with and without familial forms of PAH. An in depth understanding of the multitude of biologic variations associated with PAH may provide novel opportunities for therapeutic intervention in the coming years. This knowledge will irrevocably provide the opportunity for improved patient and family counseling as well as improved PAH diagnosis, risk assessment, and personalized treatment.

HIF2A gain-of-function mutation modulates the stiffness of smooth muscle cells and compromises vascular mechanics

Heterozygous gain-of-function (GOF) mutations of hypoxia-inducible factor 2α (HIF2A), a key hypoxia-sensing regulator, are associated with erythrocytosis, thrombosis, and vascular complications that account for morbidity and mortality of patients. We demonstrated that the vascular pathology of HIF2A GOF mutations is independent of erythrocytosis. We generated HIF2A GOF-induced pluripotent stem cells (iPSCs) and differentiated them into endothelial cells (ECs) and smooth muscle cells (SMCs). Unexpectedly, HIF2A-SMCs, but not HIF2A-ECs, were phenotypically aberrant, more contractile, stiffer, and overexpressed endothelin 1 (EDN1), myosin heavy chain, elastin, and fibrillin. EDN1 inhibition and knockdown of EDN1-receptors both reduced HIF2-SMC stiffness. Hif2A GOF heterozygous mice displayed pulmonary hypertension, had SMCs with more disorganized stress fibers and higher stiffness in their pulmonary arterial smooth muscle cells, and had more deformable pulmonary arteries compared with wild-type mice. Our findings suggest that targeting these vascular aberrations could benefit patients with HIF2A GOF and conditions of augmented hypoxia signaling.

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HIF2-SMCs are stiffer than WT-SMCs and differ in contractile SMC marker expression

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HIF2-SMCs and WT-SMCs differ in EDN1 production and ECM composition

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HIF- 2α induces EDN1; EDNI subsequently induces SMC stiffening

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Hif2A GOF mouse arterial SMCs have more disorganized stress fibers and are stiffer

Therapeutic efficacy of the novel selective RNA polymerase I inhibitor CX-5461 on pulmonary arterial hypertension and associated vascular remodelling

Background and Purpose

CX‐5461 is a novel selective RNA polymerase I (Pol I) inhibitor. Previously, we found that CX‐5461 could inhibit pathological arterial remodelling caused by angioplasty and transplantation. In the present study, we explored the pharmacological effects of CX‐5461 on experimental pulmonary arterial hypertension (PAH) and PAH‐associated vascular remodelling.

Experimental Approach

PAH was induced in Sprague–Dawley rats by monocrotaline or Sugen/hypoxia.

Key Results

We demonstrated that CX‐5461 was well tolerated for in vivo treatments. CX‐5461 prevented the development of pulmonary arterial remodelling, perivascular inflammation, pulmonary hypertension, and improved survival. More importantly, CX‐5461 partly reversed established pulmonary hypertension. In vitro, CX‐5461 induced cell cycle arrest in human pulmonary arterial smooth muscle cells. The beneficial effects of CX‐5461 in vivo and in vitro were associated with increased activation (phosphorylation) of p53.

Conclusion and Implications

Our results suggest that pharmacological inhibition of Pol I may be a novel therapeutic strategy to treat otherwise drug‐resistant PAH.