Hypoxic activation of adventitial fibroblasts: role in vascular remodeling

Pathophysiology of Group 3 Pulmonary Hypertension Associated with Lung Diseases and/or Hypoxia

Pulmonary hypertension associated with lung diseases and/or hypoxia is classified as group 3 in the clinical classification of pulmonary hypertension. The efficacy of existing selective pulmonary vasodilators for group 3 pulmonary hypertension is still unknown, and it is currently associated with a poor prognosis. The mechanisms by which pulmonary hypertension occurs include hypoxic pulmonary vasoconstriction, pulmonary vascular remodeling, a decrease in pulmonary vascular beds, endothelial dysfunction, endothelial-to-mesenchymal transition, mitochondrial dysfunction, oxidative stress, hypoxia-inducible factors (HIFs), inflammation, microRNA, and genetic predisposition. Among these, hypoxic pulmonary vasoconstriction and subsequent pulmonary vascular remodeling are characteristic factors involving the pulmonary vasculature and are the focus of this review. Several factors have been reported to mediate vascular remodeling induced by hypoxic pulmonary vasoconstriction, such as HIF-1α and mechanosensors, including TRP channels. New therapies that target novel molecules, such as mechanoreceptors, to inhibit vascular remodeling are awaited.

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.

Vascular remodelling in cardiovascular diseases: hypertension, oxidation, and inflammation

Optimal vascular structure and function are essential for maintaining the physiological functions of the cardiovascular system. Vascular remodelling involves changes in vessel structure, including its size, shape, cellular and molecular composition. These changes result from multiple risk factors and may be compensatory adaptations to sustain blood vessel function. They occur in diverse cardiovascular pathologies, from hypertension to heart failure and atherosclerosis. Dynamic changes in the endothelium, fibroblasts, smooth muscle cells, pericytes or other vascular wall cells underlie remodelling. In addition, immune cells, including macrophages and lymphocytes, may infiltrate vessels and initiate inflammatory signalling. They contribute to a dynamic interplay between cell proliferation, apoptosis, migration, inflammation, and extracellular matrix reorganisation, all critical mechanisms of vascular remodelling. Molecular pathways underlying these processes include growth factors (e.g., vascular endothelial growth factor and platelet-derived growth factor), inflammatory cytokines (e.g., interleukin-1β and tumour necrosis factor-α), reactive oxygen species, and signalling pathways, such as Rho/ROCK, MAPK, and TGF-β/Smad, related to nitric oxide and superoxide biology. MicroRNAs and long noncoding RNAs are crucial epigenetic regulators of gene expression in vascular remodelling. We evaluate these pathways for potential therapeutic targeting from a clinical translational perspective. In summary, vascular remodelling, a coordinated modification of vascular structure and function, is crucial in cardiovascular disease pathology.

Obstructive sleep apnea hypopnea syndrome and vascular lesions: An update on what we currently know

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is the most prevalent sleep and respiratory disorder. This syndrome can induce severe cardiovascular and cerebrovascular complications, and intermittent hypoxia is a pivotal contributor to this damage. Vascular pathology is closely associated with the impairment of target organs, marking a focal point in current research. Vascular lesions are the fundamental pathophysiological basis of multiorgan ailments and indicate a shared pathogenic mechanism among common cardiovascular and cerebrovascular conditions, suggesting their importance as a public health concern. Increasing evidence shows a strong correlation between OSAHS and vascular lesions. Previous studies predominantly focused on the pathophysiological alterations in OSAHS itself, such as intermittent hypoxia and fragmented sleep, leading to vascular disruptions. This review aims to delve deeper into the vascular lesions affected by OSAHS by examining the microscopic pathophysiological mechanisms involved. Emphasis has been placed on examining how OSAHS induces vascular lesions through disruptions in the endothelial barrier, metabolic dysregulation, cellular phenotype alterations, neuroendocrine irregularities, programmed cell death, vascular inflammation, oxidative stress and epigenetic modifications. This review examines the epidemiology and associated risk factors for OSAHS and vascular diseases and subsequently describes the existing evidence on vascular lesions induced by OSAHS in the cardiovascular, cerebrovascular, retinal, renal and reproductive systems. A detailed account of the current research on the pathophysiological mechanisms mediating vascular lesions caused by OSAHS is provided, culminating in a discussion of research advancements in therapeutic modalities to mitigate OSAHS-related vascular lesions and the implications of these treatment strategies.

Paeoniflorin attenuates cuproptosis and ameliorates left ventricular remodeling after AMI in hypobaric hypoxia environments

This study investigates the cardioprotective effects of Paeoniflorin (PF) on left ventricular remodeling following acute myocardial infarction (AMI) under conditions of hypobaric hypoxia. Left ventricular remodeling post-AMI plays a pivotal role in exacerbating heart failure, especially at high altitudes. Using a rat model of AMI, the study aimed to evaluate the cardioprotective potential of PF under hypobaric hypoxia. Ninety male rats were divided into four groups: sham-operated controls under normoxia/hypobaria, an AMI model group, and a PF treatment group. PF was administered for 4 weeks after AMI induction. Left ventricular function was assessed using cardiac magnetic resonance imaging. Biochemical assays of cuproptosis, oxidative stress, apoptosis, inflammation, and fibrosis were performed. Results demonstrated PF significantly improved left ventricular function and remodeling after AMI under hypobaric hypoxia. Mechanistically, PF decreased FDX1/DLAT expression and serum copper while increasing pyruvate. It also attenuated apoptosis, inflammation, and fibrosis by modulating Bcl-2, Bax, NLRP3, and oxidative stress markers. Thus, PF exhibits therapeutic potential for left ventricular remodeling post-AMI at high altitude by inhibiting cuproptosis, inflammation, apoptosis and fibrosis. Further studies are warranted to optimize dosage and duration and elucidate PF's mechanisms of action.

Obstructive Sleep Apnea and Pulmonary Hypertension: A Chicken-and-Egg Relationship

Obstructive sleep apnea (OSA) is characterized by repeated episodes of upper airway obstruction during sleep, and it is closely linked to several cardiovascular issues due to intermittent hypoxia, nocturnal hypoxemia, and disrupted sleep patterns. Pulmonary hypertension (PH), identified by elevated pulmonary arterial pressure, shares a complex interplay with OSA, contributing to cardiovascular complications and morbidity. The prevalence of OSA is alarmingly high, with studies indicating rates of 20-30% in males and 10-15% in females, escalating significantly with age and obesity. OSA's impact on cardiovascular health is profound, particularly in exacerbating conditions like systemic hypertension and heart failure. The pivotal role of hypoxemia increases intrathoracic pressure, inflammation, and autonomic nervous system dysregulation in this interplay, which all contribute to PH's pathogenesis. The prevalence of PH among OSA patients varies widely, with studies reporting rates from 15% to 80%, highlighting the variability in diagnostic criteria and methodologies. Conversely, OSA prevalence among PH patients also remains high, often exceeding 25%, stressing the need for careful screening and diagnosis. Treatment strategies like continuous positive airway pressure (CPAP) therapy show promise in mitigating PH progression in OSA patients. However, this review underscores the need for further research into long-term outcomes and the efficacy of these treatments. This review provides comprehensive insights into the epidemiology, pathophysiology, and treatment of the intricate interplay between OSA and PH, calling for integrated, personalized approaches in diagnosis and management. The future landscape of OSA and PH management hinges on continued research, technological advancements, and a holistic approach to improving patient outcomes.

The role of transcription factors in the pathogenesis and therapeutic targeting of vascular diseases

Transcription factors (TFs) constitute an essential component of epigenetic regulation. They contribute to the progression of vascular diseases by regulating epigenetic gene expression in several vascular diseases. Recently, numerous regulatory mechanisms related to vascular pathology, ranging from general TFs that are continuously activated to histiocyte-specific TFs that are activated under specific circumstances, have been studied. TFs participate in the progression of vascular-related diseases by epigenetically regulating vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs). The Krüppel-like family (KLF) TF family is widely recognized as the foremost regulator of vascular diseases. KLF11 prevents aneurysm progression by inhibiting the apoptosis of VSMCs and enhancing their contractile function. The presence of KLF4, another crucial member, suppresses the progression of atherosclerosis (AS) and pulmonary hypertension by attenuating the formation of VSMCs-derived foam cells, ameliorating endothelial dysfunction, and inducing vasodilatory effects. However, the mechanism underlying the regulation of the progression of vascular-related diseases by TFs has remained elusive. The present study categorized the TFs involved in vascular diseases and their regulatory mechanisms to shed light on the potential pathogenesis of vascular diseases, and provide novel insights into their diagnosis and treatment.

Single-nucleus ribonucleic acid-sequencing and spatial transcriptomics reveal the cardioprotection of Shexiang Baoxin Pill (SBP) in mice with myocardial ischemia-reperfusion injury

Aim: The Shexiang Baoxin Pill (SBP) has been extensively used to treat cardiovascular diseases in China for four decades, and its clinical efficacy has been widely approved. However, the mechanism by which this is achieved remains largely unexplored. Research attempting to understand the underlying mechanism is ongoing, but the findings are controversial. Here, we aimed to explore the possible mechanism of SBP in myocardial ischemia-reperfusion (I/R) injury using heart single-nucleus and spatial ribonucleic acid (RNA) sequencing. Methods: We established a murine myocardial I/R injury model in C57BL/6 mice by ligating and recanalizing the left coronary artery anterior descending branch. Subsequently, single-nucleus RNA-seq and spatial transcriptomics were performed on mice cardiac tissue. We initially assessed the status of cell types and subsets in the model administered with or without SBP. Results: We used single-nucleus RNA sequencing to comprehensively analyze cell types in the cardiac tissue of sham, I/R, and SBP mice. Nine samples from nine individuals were analyzed, and 75,546 cells were obtained. We classified the cells into 28 clusters based on their expression characteristics and annotated them into seven cell types: cardiomyocytes, endothelial cells, fibroblasts, myeloid cells, smooth muscle cells, B cells, and T cells. The SBP group had distinct cellular compositions and features than the I/R group. Furthermore, SBP-induced cardioprotection against I/R was associated with enhanced cardiac contractility, reduced endocardial cell injury, increased endocardial-mediated angiogenesis, and inhibited fibroblast proliferation. In addition, macrophages had active properties. Conclusion: SBP improves the early LVEF of I/R mice and has a cardioprotective effect. Through sequencing analysis, we observed that SBP can increase the gene expression of Nppb and Npr3 in the infarct area of the heart. Npr3 is related to vascular generation mediated by endocardial cells and requires further research. In addition, SBP increases the number of fibroblasts, inhibits the expression of genes related to fibroblast activation and proliferation, and increases the transformation of endothelial cells into fibroblasts. These findings will help to indicate directions for further research.

Mitochondrial dynamics in vascular remodeling and target-organ damage

Vascular remodeling is the pathological basis for the development of many cardiovascular diseases. The mechanisms underlying endothelial cell dysfunction, smooth muscle cell phenotypic switching, fibroblast activation, and inflammatory macrophage differentiation during vascular remodeling remain elusive. Mitochondria are highly dynamic organelles. Recent studies showed that mitochondrial fusion and fission play crucial roles in vascular remodeling and that the delicate balance of fusion-fission may be more important than individual processes. In addition, vascular remodeling may also lead to target-organ damage by interfering with the blood supply to major body organs such as the heart, brain, and kidney. The protective effect of mitochondrial dynamics modulators on target-organs has been demonstrated in numerous studies, but whether they can be used for the treatment of related cardiovascular diseases needs to be verified in future clinical studies. Herein, we summarize recent advances regarding mitochondrial dynamics in multiple cells involved in vascular remodeling and associated target-organ damage.

Noncanonical HIPPO/MST Signaling via BUB3 and FOXO Drives Pulmonary Vascular Cell Growth and Survival

RATIONALE

The MSTs (mammalian Ste20-like kinases) 1/2 are members of the HIPPO pathway that act as growth suppressors in adult proliferative diseases. Pulmonary arterial hypertension (PAH) manifests by increased proliferation and survival of pulmonary vascular cells in small PAs, pulmonary vascular remodeling, and the rise of pulmonary arterial pressure. The role of MST1/2 in PAH is currently unknown.

OBJECTIVE

To investigate the roles and mechanisms of the action of MST1 and MST2 in PAH.

METHODS AND RESULTS

Using early-passage pulmonary vascular cells from PAH and nondiseased lungs and mice with smooth muscle-specific tamoxifen-inducible Mst1/2 knockdown, we found that, in contrast to canonical antiproliferative/proapoptotic roles, MST1/2 act as proproliferative/prosurvival molecules in human PAH pulmonary arterial vascular smooth muscle cells and pulmonary arterial adventitial fibroblasts and support established pulmonary vascular remodeling and pulmonary hypertension in mice with SU5416/hypoxia-induced pulmonary hypertension. By using unbiased proteomic analysis, gain- and loss-of function approaches, and pharmacological inhibition of MST1/2 kinase activity by XMU-MP-1, we next evaluated mechanisms of regulation and function of MST1/2 in PAH pulmonary vascular cells. We found that, in PAH pulmonary arterial adventitial fibroblasts, the proproliferative function of MST1/2 is caused by IL-6-dependent MST1/2 overexpression, which induces PSMC6-dependent downregulation of forkhead homeobox type O 3 and hyperproliferation. In PAH pulmonary arterial vascular smooth muscle cells, MST1/2 acted via forming a disease-specific interaction with BUB3 and supported ECM (extracellular matrix)- and USP10-dependent BUB3 accumulation, upregulation of Akt-mTORC1, cell proliferation, and survival. Supporting our in vitro observations, smooth muscle-specific Mst1/2 knockdown halted upregulation of Akt-mTORC1 in small muscular PAs of mice with SU5416/hypoxia-induced pulmonary hypertension.

CONCLUSIONS

Together, this study describes a novel proproliferative/prosurvival role of MST1/2 in PAH pulmonary vasculature, provides a novel mechanistic link from MST1/2 via BUB3 and forkhead homeobox type O to the abnormal proliferation and survival of pulmonary arterial vascular smooth muscle cells and pulmonary arterial adventitial fibroblasts, remodeling and pulmonary hypertension, and suggests new target pathways for therapeutic intervention.

A novel nonlocal partial differential equation model of endothelial progenitor cell cluster formation during the early stages of vasculogenesis

The formation of new vascular networks is essential for tissue development and regeneration, in addition to playing a key role in pathological settings such as ischemia and tumour development. Experimental findings in the past two decades have led to the identification of a new mechanism of neovascularisation, known as cluster-based vasculogenesis, during which endothelial progenitor cells (EPCs) mobilised from the bone marrow are capable of bridging distant vascular beds in a variety of hypoxic settings in vivo. This process is characterised by the formation of EPC clusters during its early stages and, while much progress has been made in identifying various mechanisms underlying cluster formation, we are still far from a comprehensive description of such spatio-temporal dynamics. In order to achieve this, we propose a novel mathematical model of the early stages of cluster-based vasculogenesis, comprising of a system of nonlocal partial differential equations including key mechanisms such as endogenous chemotaxis, matrix degradation, cell proliferation and cell-to-cell adhesion. We conduct a linear stability analysis on the system and solve the equations numerically. We then conduct a parametric analysis of the numerical solutions of the one-dimensional problem to investigate the role of underlying dynamics on the speed of cluster formation and the size of clusters, measured via appropriate metrics for the cluster width and compactness. We verify the key results of the parametric analysis with simulations of the two-dimensional problem. Our results, which qualitatively compare with data from in vitro experiments, elucidate the complementary role played by endogenous chemotaxis and matrix degradation in the formation of clusters, suggesting chemotaxis is responsible for the cluster topology while matrix degradation is responsible for the speed of cluster formation. Our results also indicate that the nonlocal cell-to-cell adhesion term in our model, even though it initially causes cells to aggregate, is not sufficient to ensure clusters are stable over long time periods. Consequently, new modelling strategies for cell-to-cell adhesion are required to stabilise in silico clusters. We end the paper with a thorough discussion of promising, fruitful future modelling and experimental research perspectives.

Application of 7.0 T ultra-high-field MRI in evaluating the structure and function of the right ventricle of the heart in rats under a chronic hypoxic environment at high altitude

Background

Long-term exposure to a high-altitude environment with low pressure and low oxygen can cause abnormalities in the structure and function of the heart, in particular the right ventricle. Monitoring the structure and function of the right ventricle is therefore essential for early diagnosis and prognosis of high-altitude heart-related diseases. In this study, 7.0 T MRI is used to detect cardiac structure and function indicators of rats in natural plateau and plain environments.

Methods

Rats in two groups were raised in different environments from 6 weeks of age for a period of 12 weeks. At 18 weeks of age both groups underwent 7.0 T cardiac magnetic resonance (CMR) scanning. Professional cardiac post-processing software was used to analyze right ventricular end-diastolic volume (RVEDV), right ventricular end-systolic volume (RVESV), right ventricular stroke volume (RVSV), right ventricular ejection fraction (RVEF), Right ventricular end-diastolic myocardial mass (RV Myo mass, diast), Right ventricular end-systolic myocardial mass (RV Myo mass, syst), tricuspid valve end-diastolic caliber (TVD), tricuspid valve end-systolic caliber (TVS), right ventricular end-systolic long-axis (RVESL) and right ventricular end-diastolic long-axis (RVEDL). Prior to the CMR scan, blood was collected from the two groups of rats for evaluation of blood indicators. After the scan, the rats were sacrificed and the myocardial tissue morphology observed under a light microscope.

Results

In the group of rats subject to chronic hypoxia at high altitude for 12 weeks (the plateau group), red blood cell (RBC) count, hemoglobin (HGB) and hematocrit (HCT) increased (P<0.05); RVEDV, RVESV, RVSV, RV Myo mass (diast), RV Myo mass (syst), TVS, RVESL, and RVEDL also increased (P<0.05). Observation of the right ventricle of rats in the plateau group using a light microscope mainly showed a slightly widened myocardial space, myocardial cell turbidity, vacuolar degeneration, myocardial interstitial edema, vascular congestion and a small amount of inflammatory cell infiltration.

Conclusions

The importance of ultra-high-field MRI for monitoring the early stages of rat heart injury has been demonstrated by studying the changes in the structure and function of the right ventricle of rats subject to chronic hypoxia at high altitude over a period of 12 weeks.

Hypoxia induces stress fiber formation in adipocytes in the early stage of obesity

In obese adipose tissue (AT), hypertrophic expansion of adipocytes is not matched by new vessel formation, leading to AT hypoxia. As a result, hypoxia inducible factor-1⍺ (HIF-1⍺) accumulates in adipocytes inducing a transcriptional program that upregulates profibrotic genes and biosynthetic enzymes such as lysyl oxidase (LOX) synthesis. This excess synthesis and crosslinking of extracellular matrix (ECM) components cause AT fibrosis. Although fibrosis is a hallmark of obese AT, the role of fibroblasts, cells known to regulate fibrosis in other fibrosis-prone tissues, is not well studied. Here we have developed an in vitro model of AT to study adipocyte-fibroblast crosstalk in a hypoxic environment. Further, this in vitro model was used to investigate the effect of hypoxia on adipocyte mechanical properties via ras homolog gene family member A (RhoA)/Rho-associated coiled-coil kinases (ROCK) signaling pathways. We confirmed that hypoxia creates a diseased phenotype by inhibiting adipocyte maturation and inducing actin stress fiber formation facilitated by myocardin-related transcription factor A (MRTF-A/MKL1) nuclear translocation. This work presents new potential therapeutic targets for obesity by improving adipocyte maturation and limiting mechanical stress in obese AT.

Inverse modeling framework for characterizing patient-specific microstructural changes in the pulmonary arteries

Microstructural changes in the pulmonary arteries associated with pulmonary arterial hypertension (PAH) is not well understood and characterized in humans. To address this issue, we developed and applied a patient-specific inverse finite element (FE) modeling framework to characterize mechanical and structural changes of the micro-constituents in the proximal pulmonary arteries using in-vivo pressure measurements and magnetic resonance images. The framework was applied using data acquired from a pediatric PAH patient and a heart transplant patient with normal pulmonary arterial pressure, which serves as control. Parameters of a constrained mixture model that are associated with the structure and mechanical properties of elastin, collagen fibers and smooth muscle cells were optimized to fit the patient-specific pressure-diameter responses of the main pulmonary artery. Based on the optimized parameters, individual stress and linearized stiffness resultants of the three tissue constituents, as well as their aggregated values, were estimated in the pulmonary artery. Aggregated stress resultant and stiffness are, respectively, 4.6 and 3.4 times higher in the PAH patient than the control subject. Stress and stiffness resultants of each tissue constituent are also higher in the PAH patient. Specifically, the mean stress resultant is highest in elastin (PAH: 69.96, control: 14.42 kPa-mm), followed by those in smooth muscle cell (PAH: 13.95, control: 4.016 kPa-mm) and collagen fibers (PAH: 13.19, control: 2.908 kPa-mm) in both the PAH patient and the control subject. This result implies that elastin may be the key load-bearing constituent in the pulmonary arteries of the PAH patient and the control subject.

Extreme Diversity of the Human Vascular Mesenchymal Cell Landscape

Background Human mesenchymal cells are culprit factors in vascular (patho)physiology and are hallmarked by phenotypic and functional heterogeneity. At present, they are subdivided by classic umbrella terms, such as "fibroblasts," "myofibroblasts," "smooth muscle cells," "fibrocytes," "mesangial cells," and "pericytes." However, a discriminative marker-based subclassification has to date not been established. Methods and Results As a first effort toward a classification scheme, a systematic literature search was performed to identify the most commonly used phenotypical and functional protein markers for characterizing and classifying vascular mesenchymal cell subpopulation(s). We next applied immunohistochemistry and immunofluorescence to inventory the expression pattern of identified markers on human aorta specimens representing early, intermediate, and end stages of human atherosclerotic disease. Included markers comprise markers for mesenchymal lineage (vimentin, FSP-1 [fibroblast-specific protein-1]/S100A4, cluster of differentiation (CD) 90/thymocyte differentiation antigen 1, and FAP [fibroblast activation protein]), contractile/non-contractile phenotype (α-smooth muscle actin, smooth muscle myosin heavy chain, and nonmuscle myosin heavy chain), and auxiliary contractile markers (h1-Calponin, h-Caldesmon, Desmin, SM22α [smooth muscle protein 22α], non-muscle myosin heavy chain, smooth muscle myosin heavy chain, Smoothelin-B, α-Tropomyosin, and Telokin) or adhesion proteins (Paxillin and Vinculin). Vimentin classified as the most inclusive lineage marker. Subset markers did not separate along classic lines of smooth muscle cell, myofibroblast, or fibroblast, but showed clear temporal and spatial diversity. Strong indications were found for presence of stem cells/Endothelial-to-Mesenchymal cell Transition and fibrocytes in specific aspects of the human atherosclerotic process. Conclusions This systematic evaluation shows a highly diverse and dynamic landscape for the human vascular mesenchymal cell population that is not captured by the classic nomenclature. Our observations stress the need for a consensus multiparameter subclass designation along the lines of the cluster of differentiation classification for leucocytes.

Adventitial growth and lung connective tissue growth factor expression in pulmonary arterioles due to hypobaric hypoxia in broilers

Forty broilers maintained under natural hypobaric hypoxia (2,638 m above sea level) and 20 maintained under relative normoxia (460 m above sea level) were selected as pulmonary hypertensive (PHB) and nonpulmonary hypertensive (NPHB), to estimate the degree of the adventitial vascular thickness in lung arterioles and connective tissue growth factor (CTGF) expression in lung. In each group, the adventitial thickness (%AT) of 20 arterioles with 100 to 250 μm of external diameter was measured in lung samples of 24 and 42-day-old broilers. Also, mRNA extraction and real-time reverse transcription-PCR analysis were used to measure lung CTGF expression. The %AT was higher in PHB at 42 D as compared to NPHB at both ages and PHB at 24 D; however, the same differences were not evidenced at 24 D. In the 2 ages evaluated, differences were observed in the %AT between broilers under hypobaric hypoxia (PHB and NPHB) and under relative normoxia (P < 0.01). In broilers subjected to relative normoxia, no significant differences were found at any of the 2 ages. The expression levels of CTGF mRNA were higher in PHB compared to NPHB at the 2 ages. The %AT was higher in PHB with high levels of expression of CTGF mRNA than those NPHB with low expression of CTGF mRNA. This study showed that adventitial thickening is part of the pulmonary hypertension (PH) physiopathology in broilers exposed to hypobaric hypoxia, in which CTGF appears to be a fibrosis enhancer. Although present data suggest that adventitial engrossment could be a time-dependent process, individual susceptibility and the variable time-course of PH pathophysiology have to be considered.

Medicinal Plants and Phytochemicals for the Treatment of Pulmonary Hypertension

Background

Pulmonary hypertension (PH) is a progressive disease that is associated with pulmonary arteries remodeling, right ventricle hypertrophy, right ventricular failure and finally death. The present study aims to review the medicinal plants and phytochemicals used for PH treatment in the period of 1994 – 2019.

Methods

PubMed, Cochrane and Scopus were searched based on pulmonary hypertension, plant and phytochemical keywords from August 23, 2019. All articles that matched the study based on title and abstract were collected, non-English, repetitive and review studies were excluded.

Results

Finally 41 studies remained from a total of 1290. The results show that many chemical treatments considered to this disease are ineffective in the long period because they have a controlling role, not a therapeutic one. On the other hand, plants and phytochemicals could be more effective due to their action on many mechanisms that cause the progression of PH.

Conclusion

Studies have shown that herbs and phytochemicals used to treat PH do their effects from six mechanisms. These mechanisms include antiproliferative, antioxidant, antivascular remodeling, anti-inflammatory, vasodilatory and apoptosis inducing actions. According to the present study, many of these medicinal plants and phytochemicals can have effects that are more therapeutic than chemical drugs if used appropriately.

Hypoxic mast cells accelerate the proliferation, collagen accumulation and phenotypic alteration of human lung fibroblasts

Pulmonary vascular remodeling and fibrosis are the critical pathological characteristics of hypoxic pulmonary hypertension. Our previous study demonstrated that hypoxia is involved in the functional alteration of lung fibroblasts, but the underlying mechanism has yet to be fully elucidated. The aim of the present study was to investigate the effect of mast cells on the proliferation, function and phenotype of fibroblasts under hypoxic conditions. Hypoxia facilitated proliferation and the secretion of proinflammatory cytokines, including tumor necrosis factor (TNF)‑α and interleukin (IL)‑6, in human mast cells (HMC‑1). RNA sequencing identified 2,077 upregulated and 2,418 downregulated mRNAs in human fetal lung fibroblasts (HFL‑1) cultured in hypoxic conditioned medium from HMC‑1 cells compared with normoxic controls, which are involved in various pathways, including extracellular matrix organization, cell proliferation and migration. Conditioned medium from hypoxic HMC‑1 cells increased the proliferation and migration capacity of HFL‑1 and triggered phenotypic transition from fibroblasts to myofibroblasts. A greater accumulation of collagen type I and III was also observed in an HFL‑1 cell culture in hypoxic conditioned medium from HMC‑1 cells, compared with HFL‑1 cells cultured in normoxic control medium. The expression of matrix metalloproteinase (MMP)‑9 and MMP‑13 was upregulated in HFL‑1 cells grown in hypoxic conditioned medium from HMC‑1 cells. Similar pathological phenomena, including accumulation of mast cells, activated collagen metabolism and vascular remodeling, were observed in a hypoxic rat model. The results of the present study provide direct evidence that the multiple effects of the hypoxic microenvironment and mast cells on fibroblasts contribute to pulmonary vascular remodeling, and this process appears to be among the most important mechanisms underlying hypoxic pulmonary hypertension.

Involvement of miR-200b-PKCα signalling in pulmonary hypertension in cor pulmonale model

The right ventricle (RV) enlargement and pulmonary fibrosis are involved in cor pulmonale. The role of miR-200b in cor pulmonale is less well understood. This study was designed to evaluate the regulatory roles of miR-200b in cor pulmonale. Cor pulmonary mouse model was built via monocrotaline injection of monocrotaline (MCT). The expression of miR-200b in the lungs, RV and left ventricle (LV) are using real-time polymerase chain reaction. The transthoracic echocardiography was employed to determine the effects of miR-200b mimics and Gö6976 injection on MCT mice. The protein levels of protein kinase C α (PKCα), collagen, and fibronectin in the lung, RV, and LV in the mice with and without miR-200b mimics and Gö6976 injection were evaluated using western blot. The expression of miR-200b decreased in MCT mice, while there was no difference in LV. Both the miR-200b mimics and Gö6976 injection reversed the muscularization in the pulmonary artery, reversed RV hypertrophy, reduced RV systolic pressure, wall thickness and pulmonary fibrosis. The injection of miR-200b can reduce the PKCα expression in the lung, RV, and LV. This study confirmed the down-regulation of miR-200b in cor pulmonale. The reverse effects of miR-200b in the present study may provide a potential tool for cor pulmonary treatment.

Hypercoagulability in Pulmonary Hypertension

Pulmonary hypertension (PH) is divided into varied pathophysiological and etiologic groupings, as classified by the World Health Organization (WHO). Pulmonary arterial hypertension (PAH), which falls under WHO group 1 PH, is a progressive and potentially fatal disease characterized by a vasoconstrictive, proliferative, and thrombotic phenotype, which leads to increased pulmonary artery pressure, right heart failure, and death. Pathologically, in situ thromboses are found in the small distal pulmonary arteries. Dysregulation of coagulation, platelet function, and endothelial cells may contribute to a prothrombotic state. There is mixed evidence for the use of anticoagulation or antiplatelet therapy in PAH patients.

Reactive Oxygen Species and Pulmonary Vasculature During Hypobaric Hypoxia

An increasing number of people are living or working at high altitudes (hypobaric hypoxia) and therefore suffering several physiological, biochemical, and molecular changes. Pulmonary vasculature is one of the main and first responses to hypoxia. These responses imply hypoxic pulmonary vasoconstriction (HPV), remodeling, and eventually pulmonary hypertension (PH). These events occur according to the type and extension of the exposure. There is also increasing evidence that these changes in the pulmonary vascular bed could be mainly attributed to a homeostatic imbalance as a result of increased levels of reactive oxygen species (ROS). The increase in ROS production during hypobaric hypoxia has been attributed to an enhanced activity and expression of nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase), though there is some dispute about which subunit is involved. This enzymatic complex may be directly induced by hypoxia-inducible factor-1α (HIF-1α). ROS has been found to be related to several pathways, cells, enzymes, and molecules in hypoxic pulmonary vasculature responses, from HPV to inflammation, and structural changes, such as remodeling and, ultimately, PH. Therefore, we performed a comprehensive review of the current evidence on the role of ROS in the development of pulmonary vasculature changes under hypoxic conditions, with a focus on hypobaric hypoxia. This review provides information supporting the role of oxidative stress (mainly ROS) in the pulmonary vasculature’s responses under hypobaric hypoxia and depicting possible future therapeutics or research targets. NADPH oxidase-produced oxidative stress is highlighted as a major source of ROS. Moreover, new molecules, such as asymmetric dimethylarginine, and critical inflammatory cells as fibroblasts, could be also involved. Several controversies remain regarding the role of ROS and the mechanisms involved in hypoxic responses that need to be elucidated.

Macrophage migration inhibitory factor (MIF) in the development and progression of pulmonary arterial hypertension

Macrophage migration inhibitory factor (MIF) has been described as a pro-inflammatory cytokine and regulator of neuro-endocrine function. It plays an important upstream role in the inflammatory cascade by promoting the release of other inflammatory cytokines such as TNF-alpha and IL-6, ultimately triggering a chronic inflammatory immune response. As lungs can synthesize and release MIF, many studies have investigated the potential role of MIF as a biomarker in assessment of patients with pulmonary arterial hypertension (PAH) and using anti-MIFs as a new therapeutic modality for PAH.

Mitochondrial dysfunction and pulmonary hypertension: cause, effect, or both

Pulmonary hypertension describes a heterogeneous disease defined by increased pulmonary artery pressures, and progressive increase in pulmonary vascular resistance due to pathologic remodeling of the pulmonary vasculature involving pulmonary endothelial cells, pericytes, and smooth muscle cells. This process occurs under various conditions, and although these populations vary, the clinical manifestations are the same: progressive dyspnea, increases in right ventricular (RV) afterload and dysfunction, RV-pulmonary artery uncoupling, and right-sided heart failure with systemic circulatory collapse. The overall estimated 5-yr survival rate is 72% in highly functioning patients, and as low as 28% for those presenting with advanced symptoms. Metabolic theories have been suggested as underlying the pathogenesis of pulmonary hypertension with growing evidence of the role of mitochondrial dysfunction involving the major proteins of the electron transport chain, redox-related enzymes, regulators of the proton gradient and calcium homeostasis, regulators of apoptosis, and mitophagy. There remain more studies needed to characterize mitochondrial dysfunction leading to impaired vascular relaxation, increase proliferation, and failure of regulatory mechanisms. The effects on endothelial cells and resulting interactions with their microenvironment remain uncharted territory for future discovery. Additionally, on the basis of observations that the "plexigenic lesions" of pulmonary hypertension resemble the unregulated proliferation of tumor cells, similarities between cancer pathobiology and pulmonary hypertension have been drawn, suggesting interactions between mitochondria and angiogenesis. Recently, mitochondria targeting has become feasible, which may yield new therapeutic strategies. We present a state-of-the-art review of the role of mitochondria in both the pathobiology of pulmonary hypertension and potential therapeutic targets in pulmonary vascular processes.

Accelerated tumour metastasis due to interferon-γ receptor-mediated dissociation of perivascular cells from blood vessels

Angiostasis mediated by interferon (IFN)-γ is a key mechanism of anti-tumour immunity; however, the effect of IFN-γ on host vascular endothelial growth factor A (VEGFA)-expressing cells during tumour progression is still elusive. Here, we developed transgenic mice with IFN-γ receptor (IFNγR) expression under control of the Vegfa promoter (V-γR). In these mice, the IFN-γ responsiveness of VEGFA-expressing cells led to dramatic growth suppression of transplanted lung carcinoma cells. Surprisingly, increased mortality and tumour metastasis were observed in the tumour-bearing V-γR mice, in comparison with the control wild-type and IFNγR-deficient mice. Further study showed that perivascular cells were VEGFA-expressing cells and potential IFN-γ targets. In vivo, tumour vascular perfusion and pericyte association with blood vessels were massively disrupted in V-γR mice. In vitro, IFN-γ inhibited transforming growth factor-β signalling by upregulating SMAD7, and therefore downregulated N-cadherin expression in pericytes. Importantly, IFN-γ neutralization in vivo with a monoclonal antibody reduced tumour metastasis. Together, the results suggest that IFNγR-mediated dissociation of perivascular cells from blood vessels contributes to the acceleration of tumour metastasis. Thus, the inhibition of tumour growth via IFN-γ-induced angiostasis might also accelerate tumour metastasis. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Expression profile of mitochondrial voltage-dependent anion channel-1 (VDAC1) influenced genes is associated with pulmonary hypertension

Several human diseases have been associated with mitochondrial voltage-dependent anion channel-1 (VDAC1) due to its role in calcium ion transportation and apoptosis. Recent studies suggest that VDAC1 may interact with endothelium-dependent nitric oxide synthase (eNOS). Decreased VDAC1 expression may limit the physical interaction between VDAC1 and eNOS and thus impair nitric oxide production, leading to cardiovascular diseases, including pulmonary arterial hypertension (PAH). In this report, we conducted meta-analysis of genome-wide expression data to identify VDAC1 influenced genes implicated in PAH pathobiology. First, we identified the genes differentially expressed between wild-type and Vdac1 knockout mouse embryonic fibroblasts in hypoxic conditions. These genes were deemed to be influenced by VDAC1 deficiency. Gene ontology analysis indicates that the VDAC1 influenced genes are significantly associated with PAH pathobiology. Second, a molecular signature derived from the VDAC1 influenced genes was developed. We suggest that, VDAC1 has a protective role in PAH and the gene expression signature of VDAC1 influenced genes can be used to i) predict severity of pulmonary hypertension secondary to pulmonary diseases, ii) differentiate idiopathic pulmonary artery hypertension (IPAH) patients from controls, and iii) differentiate IPAH from connective tissue disease associated PAH.

Characterization of a Mouse Model of Emphysema Induced by Multiple Instillations of Low-Dose Elastase

Many experimental models have been proposed to study the pathophysiological features of emphysema, as well as to search for new therapeutic approaches for acute or chronically injured lung parenchyma. We aimed to characterize an emphysema model induced by multiple instillations of elastase by tracking changes in inflammation, remodeling, and cardiac function after each instillation. Forty-eight C57BL/6 mice were randomly assigned across two groups. Emphysema (ELA) animals received 1, 2, 3, or 4 intratracheal instillations of pancreatic porcine elastase (PPE, 0.2 IU) with a 1-week interval between them. Controls (C) received saline following the same protocol. Before and after implementation of the protocol, animals underwent echocardiographic analysis. After the first instillation of PPE, the percentage of mononuclear cells in the lung parenchyma increased compared to C (p = 0.0001). The second instillation resulted in hyperinflated alveoli, increased mean linear intercept, and reduced elastic fiber content in lung parenchyma compared to C (p = 0.0197). Following the third instillation, neutrophils and collagen fiber content in alveolar septa and airways increased, whereas static lung elastance was reduced compared to C (p = 0.0094). After the fourth instillation, the percentage of M1 macrophages in lungs; levels of interleukin-1β (IL-1β), keratinocyte-derived chemokine, hepatocyte growth factor (HGF), and vascular endothelial growth factor (VEGF); and collagen fiber content in the pulmonary vessel wall were increased compared to C (p = 0.0096). At this time point, pulmonary arterial hypertension was apparent, with increased diastolic right ventricular wall thickness. In conclusion, the initial phase of emphysema was characterized by lung inflammation with predominance of mononuclear cells, whereas at the late stage, impairment of pulmonary and cardiovascular functions was observed. This model enables analysis of therapies at different time points during controlled progression of emphysema. Accordingly, early interventions could focus on the inflammatory process, while late interventions should focus on restoring cardiorespiratory function.

Role of Extracellular Adenosine Triphosphate in Human Skin

Background:

The nucleotide adenosine triphosphate (ATP) has long been known to drive and participate in countless intracellular processes. Extracellular ATP and its metabolite adenosine have also been shown to exert a variety of effects on nearly every cell type in human skin. Knowledge of the sources and effects of extracellular ATP in human skin may help shape new therapies for skin injury, inflammation, and numerous other cutaneous disorders.

Objective:

The objective of this review is to introduce the reader to current knowledge regarding the sources and effects of extracellular ATP in human skin and to outline areas in which further research is necessary to clarify the nature and mechanism of these effects.

Conclusion:

Extracellular ATP seems to play a direct role in triggering skin inflammatory, regenerative, and fibrotic responses to mechanical injury, an indirect role in melanocyte proliferation and apoptosis, and a complex role in Langerhans cell-directed adaptive immunity.

Microarray analysis in pulmonary hypertension

Microarrays are a powerful and effective tool that allows the detection of genome-wide gene expression differences between controls and disease conditions. They have been broadly applied to investigate the pathobiology of diverse forms of pulmonary hypertension, namely group 1, including patients with idiopathic pulmonary arterial hypertension, and group 3, including pulmonary hypertension associated with chronic lung diseases such as chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis. To date, numerous human microarray studies have been conducted to analyse global (lung homogenate samples), compartment-specific (laser capture microdissection), cell type-specific (isolated primary cells) and circulating cell (peripheral blood) expression profiles. Combined, they provide important information on development, progression and the end-stage disease. In the future, system biology approaches, expression of noncoding RNAs that regulate coding RNAs, and direct comparison between animal models and human disease might be of importance.

Comprehensive overview of compartment-specific microarray studies of material from pulmonary hypertension patientshttp://ow.ly/YEFO2

TGF-β1/FGF-2 signaling mediates the 15-HETE-induced differentiation of adventitial fibroblasts into myofibroblasts

Background

Pulmonary adventitial fibroblasts (PAFs) are activated under stress stimuli leading to their differentiation into myofibroblasts, which is involved in vessel remodeling. 15-HETE is known as an important factor in vessel remodeling under hypoxia; however, the role of 15-HETE in PAF phenotypic alteration is not clear.

Results

The effect of 15-HETE on PAF phenotypic alterations was investigated in the present study. PAFs were treated with 15-HETE (0.5 μM) for 24 h, and the myofibroblast marker α-smooth muscle actin (α-SMA) was analyzed. The 15-HETE induced α-SMA expression and cell morphology. 15-HETE upregulated FGF-2 levels in PAFs, and knockdown FGF-2 by siRNAs blocked the enhanced α-SMA expression induced by 15-HETE. p38 kinase was activated, and blocked depressed 15-HETE-induced FGF-2 expression. The downstream of p38 pathway, Egr-1 activation, was also raised by 15-HETE treatment, and silenced Egr-1 suppressed the 15-HETE-induced upregulation of FGF-2. TGF-β1 was upregulated with FGF-2 treatment, and α-SMA expression induced by FGF-2 was inhibited after the cell was transferred with TGF-β1 siRNA. Meanwhile, FGF-2 increased α-SMA expression and improved proliferation, which was associated with p27^kip1 and cyclin E variation.

Conclusions

The above results suggest that p38/Egr-1 pathway-mediated FGF-2 is involved in 15-HETE-induced differentiation of PAFs into myofibroblasts and cell proliferation.

Leptin knockout attenuates hypoxia-induced pulmonary arterial hypertension by inhibiting proliferation of pulmonary arterial smooth muscle cells

Pulmonary arterial hypertension (PAH) is a fatal disease characterized by excessive vascular smooth muscle cells proliferation in small pulmonary arteries, leading to elevation of pulmonary vascular resistance with consequent right ventricular (RV) failure and death. Recently, emerging evidence has shown that leptin signaling is involved in different cardiac pathologies; however, the role of leptin remains limited in the setting of PAH. Thus, in this study, we tested the hypothesis of direct involvement of leptin in the development of PAH. Our data show that leptin activity in plasma and protein level in the lung were higher in hypoxia- and monocrotaline-induced PAH models compared with control animals. Wild-type (WT) and C57BL/6J-Lep(ob) (ob/ob) male mice were exposed to normobaric hypoxia (10% O(2)) or normoxia (21% O(2)). After 2 and 4 weeks of chronic hypoxia exposure, WT mice developed PAH as reflected by the increased values of RV systolic pressure, RV hypertrophy index, the medial wall thickness of pulmonary arterioles, and muscularization of pulmonary arterioles. And, all these alterations were attenuated in ob/ob mice treated with hypoxia. Leptin could stimulate the proliferation of pulmonary arterial smooth muscle cells (PASMCs) by activating extracellular signal-regulated kinase (ERK), signal transducer and activator of transcription 3 (STAT3), and Akt pathways. These data suggest that the leptin signaling pathway is crucial for the development of PAH. Leptin activates ERK, STAT, and Akt pathways and subsequently PASMCs proliferation, providing new mechanistic information about hypoxia-induced PAH.

ROCK2 and MYLK variants under hypobaric hypoxic environment of high altitude associate with high altitude pulmonary edema and adaptation

Objective

To date, a major class of kinases, serine–threonine kinase, has been scantly investigated in stress-induced rare, fatal (if not treated early), and morbid disorder, high altitude pulmonary edema (HAPE). This study examined three major serine–threonine kinases, ROCK2, MYLK, and JNK1, along with six other genes, tyrosine hydroxylase, G-protein subunits GNA11 and GNB3, and alpha1 adrenergic receptor isoforms 1A, 1B, and 1D as candidate gene markers of HAPE and adaptation.

Methods

For this, 57 variants across these nine genes were genotyped in HAPE patients (n=225), HAPE controls (n=210), and highlanders (n=259) by Sequenom MS (TOF)-based MassARRAY® platform using iPLEX™ Gold technology. In addition, to study the gene expression, quantitative real-time polymerase chain reaction was performed in human peripheral blood mononuclear cells of the three study groups.

Results

A significant association was observed for C allele (ROCK2 single-nucleotide polymorphism, rs10929728) with HAPE (P=0.03) and C, T, and A alleles (MYLK single-nucleotide polymorphisms, rs11717814, rs40305, and rs820336) with both HAPE and adaptation (P=0.001, P=0.006, and P=0.02, respectively). ROCK2 88 kb GGGTTGGT haplotype was associated with lower risk of HAPE (P=0.0009). MYLK 7 kb haplotype CTA, composed of variant alleles, was associated with higher risk of HAPE (P=0.0006) and lower association with adaptation (P=1E–06), whereas haplotype GCG, composed of wild-type alleles, was associated with lower risk of HAPE (P=0.001) and higher association with adaptation (P=1E–06). Haplotype–haplotype and gene–gene interactions demonstrated a correlation in working of ROCK2 and MYLK.

Conclusion

The data suggest the association of ROCK2 with HAPE and MYLK with HAPE and adaptation in Indian population. The outcome has provided new insights into the physiology of HAPE and adaptation.

Significance of main pulmonary artery dilation on imaging studies

Proper and early identification of patients who harbor serious occult illness is the first step in developing a disease-management strategy. Identification of illnesses through the use of noninvasive techniques provides assurance of patient safety and is ideal. PA dilation is easily measured noninvasively and is due to a variety of conditions, including pulmonary hypertension (PH). The clinician should be able to thoroughly assess the significance of PA dilation in each individual patient. This involves knowledge of the ability of PA dilation to accurately predict PH, understand the wide differential diagnosis of causes of PA dilation, and reverse its life-threatening complications. We found that although PA dilation is suggestive of PH, data remain inconclusive regarding its ability to accurately predict PH. At this point, data are insufficient to place PA dilation into a PH risk-score equation. Here we review the causes and complications of PA dilation, define normal and abnormal PA measurements, and summarize the data linking its association to PH, while suggesting an algorithm designed to assist clinicians in patient work-up after recognizing PA dilation.

Hypoxia preconditioned mesenchymal stem cells prevent cardiac fibroblast activation and collagen production via leptin

AIMS

Activation of cardiac fibroblasts into myofibroblasts constitutes a key step in cardiac remodeling after myocardial infarction (MI), due to interstitial fibrosis. Mesenchymal stem cells (MSCs) have been shown to improve post-MI remodeling an effect that is enhanced by hypoxia preconditioning (HPC). Leptin has been shown to promote cardiac fibrosis. The expression of leptin is significantly increased in MSCs after HPC but it is unknown whether leptin contributes to MSC therapy or the fibrosis process. The objective of this study was to determine whether leptin secreted from MSCs modulates cardiac fibrosis.

METHODS

Cardiac fibroblast (CF) activation was induced by hypoxia (0.5% O2). The effects of MSCs on fibroblast activation were analyzed by co-culturing MSCs with CFs, and detecting the expression of α-SMA, SM22α, and collagen IαI in CFs by western blot, immunofluorescence and Sirius red staining. In vivo MSCs antifibrotic effects on left ventricular remodeling were investigated using an acute MI model involving permanent ligation of the left anterior descending coronary artery.

RESULTS

Co-cultured MSCs decreased fibroblast activation and HPC enhanced the effects. Leptin deficit MSCs from Ob/Ob mice did not decrease fibroblast activation. Consistent with this, H-MSCs significantly inhibited cardiac fibrosis after MI and mediated decreased expression of TGF-β/Smad2 and MRTF-A in CFs. These effects were again absent in leptin-deficient MSCs.

CONCLUSION

Our data demonstrate that activation of cardiac fibroblast was inhibited by MSCs in a manner that was leptin-dependent. The mechanism may involve blocking TGF-β/Smad2 and MRTF-A signal pathways.

Stromal fibroblast activation and their potential association with uterine fibroids (Review)

Uterine fibroids are the most common type of benign, gynecologic neoplasm and are the primary indication for performance of a hysterectomy, accounting for >200,000 hysterectomies annually in the USA. At present, females are younger and exhibit larger leiomyomas at the time of diagnosis. Cancer-associated fibroblasts in tumor microenvironments have emerged as an important target for cancer therapy. Repeated stimulation by infectious or non-infectious agents in the uterine tissues, including inflammation, mechanical forces or hypoxia, stimulate the resident fibroblasts to undergo specific activation and, thus, are significant in tumorigenesis. Furthermore, complex signaling pathways regulate the mechanisms of fibroblastic activation. The current review focuses on the molecular mechanisms of fibroblastic activation and the potential association with uterine leiomyoma pathogenesis, enabling an integrated pathogenic analysis for review of the therapeutic options.

Development and pathologies of the arterial wall

Arteries consist of an inner single layer of endothelial cells surrounded by layers of smooth muscle and an outer adventitia. The majority of vascular developmental studies focus on the construction of endothelial networks through the process of angiogenesis. Although many devastating vascular diseases involve abnormalities in components of the smooth muscle and adventitia (i.e., the vascular wall), the morphogenesis of these layers has received relatively less attention. Here, we briefly review key elements underlying endothelial layer formation and then focus on vascular wall development, specifically on smooth muscle cell origins and differentiation, patterning of the vascular wall, and the role of extracellular matrix and adventitial progenitor cells. Finally, we discuss select human diseases characterized by marked vascular wall abnormalities. We propose that continuing to apply approaches from developmental biology to the study of vascular disease will stimulate important advancements in elucidating disease mechanism and devising novel therapeutic strategies.

Regulation of hypoxia-induced pulmonary hypertension by vascular smooth muscle hypoxia-inducible factor-1α

RATIONALE

Chronic hypoxia induces pulmonary vascular remodeling, pulmonary hypertension, and right ventricular hypertrophy. At present, little is known about mechanisms driving these responses. Hypoxia-inducible factor-1α (HIF-1α) is a master regulator of transcription in hypoxic cells, up-regulating genes involved in energy metabolism, proliferation, and extracellular matrix reorganization. Systemic loss of a single HIF-1α allele has been shown to attenuate hypoxic pulmonary hypertension, but the cells contributing to this response have not been identified.

OBJECTIVES

We sought to determine the contribution of HIF-1α in smooth muscle on pulmonary vascular and right heart responses to chronic hypoxia.

METHODS

We used mice with homozygous conditional deletion of HIF-1α combined with tamoxifen-inducible smooth muscle-specific Cre recombinase expression. Mice received either tamoxifen or vehicle followed by exposure to either normoxia or chronic hypoxia (10% O2) for 30 days before measurement of cardiopulmonary responses.

MEASUREMENTS AND MAIN RESULTS

Tamoxifen-induced smooth muscle-specific deletion of HIF-1α attenuated pulmonary vascular remodeling and pulmonary hypertension in chronic hypoxia. However, right ventricular hypertrophy was unchanged despite attenuated pulmonary pressures.

CONCLUSIONS

These results indicate that HIF-1α in smooth muscle contributes to pulmonary vascular remodeling and pulmonary hypertension in chronic hypoxia. However, loss of HIF-1 function in smooth muscle does not affect hypoxic cardiac remodeling, suggesting that the cardiac hypertrophy response is not directly coupled to the increase in pulmonary artery pressure.

Regulation of hypoxia-induced pulmonary hypertension by vascular smooth muscle hypoxia-inducible factor-1α

RATIONALE

Chronic hypoxia induces pulmonary vascular remodeling, pulmonary hypertension, and right ventricular hypertrophy. At present, little is known about mechanisms driving these responses. Hypoxia-inducible factor-1α (HIF-1α) is a master regulator of transcription in hypoxic cells, up-regulating genes involved in energy metabolism, proliferation, and extracellular matrix reorganization. Systemic loss of a single HIF-1α allele has been shown to attenuate hypoxic pulmonary hypertension, but the cells contributing to this response have not been identified.

OBJECTIVES

We sought to determine the contribution of HIF-1α in smooth muscle on pulmonary vascular and right heart responses to chronic hypoxia.

METHODS

We used mice with homozygous conditional deletion of HIF-1α combined with tamoxifen-inducible smooth muscle-specific Cre recombinase expression. Mice received either tamoxifen or vehicle followed by exposure to either normoxia or chronic hypoxia (10% O2) for 30 days before measurement of cardiopulmonary responses.

MEASUREMENTS AND MAIN RESULTS

Tamoxifen-induced smooth muscle-specific deletion of HIF-1α attenuated pulmonary vascular remodeling and pulmonary hypertension in chronic hypoxia. However, right ventricular hypertrophy was unchanged despite attenuated pulmonary pressures.

CONCLUSIONS

These results indicate that HIF-1α in smooth muscle contributes to pulmonary vascular remodeling and pulmonary hypertension in chronic hypoxia. However, loss of HIF-1 function in smooth muscle does not affect hypoxic cardiac remodeling, suggesting that the cardiac hypertrophy response is not directly coupled to the increase in pulmonary artery pressure.

Soluble receptor for advanced glycation end products (sRAGE) attenuates haemodynamic changes to chronic hypoxia in the mouse

The calgranulin-like protein MTS1/S100A4 and the receptor for advanced glycation end-products (RAGE) have recently been implicated in mediating pulmonary arterial smooth muscle cell proliferation and vascular remodelling in experimental pulmonary arterial hypertension (PH). Here, the effects of RAGE antagonism upon 2 weeks of hypobaric hypoxia (10% O2)-induced PH in mice were assessed. Treatment with sRAGE was protective against hypobaric hypoxia-induced increases in right ventricular pressure but distal pulmonary vascular remodelling was unaffected. Intralobar pulmonary arteries from hypobaric hypoxic mice treated with sRAGE showed protection against a hypoxia-induced reduction in compliance. However, a combination of sRAGE and hypoxia also dramatically increased the force of contractions to KCl and 5-HT observed in these vessels. The acute addition of sRAGE to the organ bath produced a small, sustained contraction in intralobar pulmonary vessels and produced a synergistic enhancement of the maximal force of contraction in subsequent concentration-response curves to 5-HT. sRAGE had no effect on 5-HT-induced proliferation of Chinese hamster lung fibroblasts (CCL39), used since they have a similar pharmacological profile to mouse pulmonary fibroblasts but, surprisingly, produced a marked increase in hypoxia-induced proliferation. These data implicate RAGE as a modulator of both vasoreactivity and of proliferative processes in the response of the pulmonary circulation to chronic-hypoxia.

Cellular mechanisms of tissue fibrosis. 6. Purinergic signaling and response in fibroblasts and tissue fibrosis

Tissue fibrosis occurs as a result of the dysregulation of extracellular matrix (ECM) synthesis. Tissue fibroblasts, resident cells responsible for the synthesis and turnover of ECM, are regulated via numerous hormonal and mechanical signals. The release of intracellular nucleotides and their resultant autocrine/paracrine signaling have been shown to play key roles in the homeostatic maintenance of tissue remodeling and in fibrotic response post-injury. Extracellular nucleotides signal through P2 nucleotide and P1 adenosine receptors to activate signaling networks that regulate the proliferation and activity of fibroblasts, which, in turn, influence tissue structure and pathologic remodeling. An important component in the signaling and functional responses of fibroblasts to extracellular ATP and adenosine is the expression and activity of ectonucleotideases that attenuate nucleotide-mediated signaling, and thereby integrate P2 receptor- and subsequent adenosine receptor-initiated responses. Results of studies of the mechanisms of cellular nucleotide release and the effects of this autocrine/paracrine signaling axis on fibroblast-to-myofibroblast conversion and the fibrotic phenotype have advanced understanding of tissue remodeling and fibrosis. This review summarizes recent findings related to purinergic signaling in the regulation of fibroblasts and the development of tissue fibrosis in the heart, lungs, liver, and kidney.

The adventitia: Essential role in pulmonary vascular remodeling

A rapidly emerging concept is that the vascular adventitia acts as a biological processing center for the retrieval, integration, storage, and release of key regulators of vessel wall function. It is the most complex compartment of the vessel wall and comprises a variety of cells including fibroblasts, immunomodulatory cells, resident progenitor cells, vasa vasorum endothelial cells, and adrenergic nerves. In response to vascular stress or injury, resident adventitial cells are often the first to be activated and reprogrammed to then influence tone and structure of the vessel wall. Experimental data indicate that the adventitial fibroblast, the most abundant cellular constituent of adventitia, is a critical regulator of vascular wall function. In response to vascular stresses such as overdistension, hypoxia, or infection, the adventitial fibroblast is activated and undergoes phenotypic changes that include proliferation, differentiation, and production of extracellular matrix proteins and adhesion molecules, release of reactive oxygen species, chemokines, cytokines, growth factors, and metalloproteinases that, collectively, affect medial smooth muscle cell tone and growth directly and that stimulate recruitment and retention of circulating inflammatory and progenitor cells to the vessel wall. Resident dendritic cells also participate in "sensing" vascular stress and actively communicate with fibroblasts and progenitor cells to simulate repair processes that involve expansion of the vasa vasorum, which acts as a conduit for further delivery of inflammatory/progenitor cells. This review presents the current evidence demonstrating that the adventitia acts as a key regulator of pulmonary vascular wall function and structure from the "outside in."

Genomics and proteomics of pulmonary vascular disease

Study of RNA and proteins in cells of both normal and diseased tissues is providing researchers with new knowledge of disease pathologies. While still in its early stages, high-throughput expression analysis is improving our understanding of the pathogenesis of pulmonary arterial hypertension (PAH). While many studies have used microarray and proteomic analyses as "hypothesis-generating" tools, the technologies also have potential to identify and quantify biomarkers of disease. To date, many of the published studies have examined gene expression profiles of tissue biopsies, others have utilized cells from peripheral blood. Microarray technology has been employed successfully in the investigation of a diverse array of human diseases. The potential of high-throughput expression analysis to improve our understanding of the pathogenesis of PAH is highlighted in this review. Proteomic studies of PAH and pulmonary vascular diseases in general have been little utilized thus far. To date, such studies are few and no consistent biomarker has emerged from studies of either plasma or blood cells from idiopathic pulmonary arterial hypertension (IPAH) patients. The studies of both lung tissue and lymphocytes are perhaps more revealing and suggest that changes in the cytoskeletal machinery may play a role in the pathogenesis of idiopathic pulmonary arterial hypertension. The oncology literature has demonstrated the utility of gene microarray analysis to predict important outcomes such as response to therapy and survival. It is likely that in the near future, gene microarrays and proteomic analyses will also be employed in a pharmacogenomics approach in PAH, helping to identify the most appropriate therapies for individual patients.

Placenta growth factor mediates angiogenesis in hypoxic pulmonary hypertension

Our previous studies have proved that hypoxia enhances the 15-lipoxygenase (15-LO) expression and increases endogenous 15-hydroxyeicosatetraenoic acid (15-HETE) production to promote pulmonary vascular remodeling and angiogenesis, while the mechanisms of how hypoxia regulates 15-LO expression in endothelium is still unknown. As placenta growth factor (PlGF) promotes pathological angiogenesis by acting on the growth, migration and survival of endothelial cells, there may be some connections between PlGF and 15-LO in hypoxia induced endothelial cells proliferation. In this study, we performed immunohistochemistry, pulmonary artery endothelial cells migration and bromodeoxyuridine incorporation to determine the role of PlGF in pulmonary remodeling induced by hypoxia. Our results showed that hypoxia up-regulated PlGF expression, which was mediated by 15-LO/15-HETE pathway. Furthermore, we found that PlGF had a positive feedback regulation with 15-LO expression and 15-HETE generation. The interaction in hypoxia between 15-HETE and PlGF created a PlGF-15-LO-15-HETE loop, leading to endothelial dysfunction. Thus, these findings suggest a new therapeutic agent in combination with the blockade of PlGF as well as 15-LO in hypoxic pulmonary hypertension.

Cooperation by fibroblasts and bone marrow-mesenchymal stem cells to improve pancreatic rat-to-mouse islet xenotransplantation

Experimental and clinical experiences highlight the need to review some aspects of islet transplantation, especially with regard to site of grafting and control of the immune response. The subcutaneous space could be a good alternative to liver but its sparse vasculature is its main limitation. Induction of graft tolerance by using cells with immunoregulatory properties is a promising approach to avoid graft rejection. Both Fibroblasts and Mesenchymal Stem Cells (MSCs) have shown pro-angiogenic and immunomodulatory properties. Transplantation of islets into the subcutaneous space using plasma as scaffold and supplemented with fibroblasts and/or Bone Marrow-MSCs could be a promising strategy to achieve a functional extra-hepatic islet graft, without using immunosuppressive drugs. Xenogenic rat islets, autologous fibroblasts and/or allogenic BM-MSCs, were mixed with plasma, and coagulation was induced to constitute a Plasma-based Scaffold containing Islets (PSI), which was transplanted subcutaneously both in immunodeficient and immunocompetent diabetic mice. In immunodeficient diabetic mice, PSI itself allowed hyperglycemia reversion temporarily, but the presence of pro-angiogenic cells (fibroblasts or BM-MSCs) within PSI was necessary to improve graft re-vascularization and, thus, consistently maintain normoglycemia. In immunocompetent diabetic mice, only PSI containing BM-MSCs, but not those containing fibroblasts, normalized glycemia lasting up to one week after transplantation. Interestingly, when PSI contained both fibroblasts and BM-MSCs, the normoglycemia period showed an increase of 4-times with a physiological-like response in functional tests. Histology of immunocompetent mice showed an attenuation of the immune response in those grafts with BM-MSCs, which was improved by co-transplantation with fibroblasts, since they increased BM-MSC survival. In summary, fibroblasts and BM-MSCs showed similar pro-angiogenic properties in this model of islet xenotransplantation, whereas only BM-MSCs exerted an immunomodulatory effect, which was improved by the presence of fibroblasts. These results suggest that cooperation of different cell types with islets will be required to achieve a long-term functional graft.

Pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a chronic and progressive disease leading to right heart failure and ultimately death if untreated. The first classification of PH was proposed in 1973. In 2008, the fourth World Symposium on PH held in Dana Point (California, USA) revised previous classifications. Currently, PH is devided into five subgroups. Group 1 includes patients suffering from idiopathic or familial PAH with or without germline mutations. Patients with a diagnosis of PAH should systematically been screened regarding to underlying mutations of BMPR2 gene (bone morphogenetic protein receptor type 2) or more rarely of ACVRL1 (activine receptor-like kinase type 1), ENG (endogline) or Smad8 genes. Pulmonary veno occusive disease and pulmonary capillary hemagiomatosis are individualized and designated as clinical group 1'. Group 2 'Pulmonary hypertension due to left heart diseases' is divided into three sub-groups: systolic dysfonction, diastolic dysfonction and valvular dysfonction. Group 3 'Pulmonary hypertension due to respiratory diseases' includes a heterogenous subgroup of respiratory diseases like PH due to pulmonary fibrosis, COPD, lung emphysema or interstitial lung disease for exemple. Group 4 includes chronic thromboembolic pulmonary hypertension without any distinction of proximal or distal forms. Group 5 regroup PH patients with unclear multifactorial mechanisms. Invasive hemodynamic assessment with right heart catheterization is requested to confirm the definite diagnosis of PH showing a resting mean pulmonary artery pressure (mPAP) of ≥ 25 mmHg and a normal pulmonary capillary wedge pressure (PCWP) of ≤ 15 mmHg. The assessment of PCWP may allow the distinction between pre-capillary and post-capillary PH (PCWP > 15 mmHg). Echocardiography is an important tool in the management of patients with underlying suspicion of PH. The European Society of Cardiology and the European Respiratory Society (ESC-ERS) guidelines specify its role, essentially in the screening proposing criteria for estimating the presence of PH mainly based on tricuspid regurgitation peak velocity and systolic artery pressure (sPAP). The therapy of PAH consists of non-specific drugs including oral anticoagulation and diuretics as well as PAH specific therapy. Diuretics are one of the most important treatment in the setting of PH because right heart failure leads to fluid retention, hepatic congestion, ascites and peripheral edema. Current recommendations propose oral anticoagulation aiming for targeting an International Normalized Ratio (INR) between 1.5-2.5. Target INR for patients displaying chronic thromboembolic PH is between 2–3. Better understanding in pathophysiological mechanisms of PH over the past quarter of a century has led to the development of medical therapeutics, even though no cure for PAH exists. Several specific therapeutic agents were developed for the medical management of PAH including prostanoids (epoprostenol, trepoprostenil, iloprost), endothelin receptor antagonists (bosentan, ambrisentan) and phosphodiesterase type 5 inhibitors (sildenafil, tadalafil). This review discusses the current state of art regarding to epidemiologic aspects of PH, diagnostic approaches and the current classification of PH. In addition, currently available specific PAH therapy is discussed as well as future treatments.

MicroRNAs in pulmonary arterial remodeling

Pulmonary arterial remodeling is a presently irreversible pathologic hallmark of pulmonary arterial hypertension (PAH). This complex disease involves pathogenic dysregulation of all cell types within the small pulmonary arteries contributing to vascular remodeling leading to intimal lesions, resulting in elevated pulmonary vascular resistance and right heart dysfunction. Mutations within the bone morphogenetic protein receptor 2 gene, leading to dysregulated proliferation of pulmonary artery smooth muscle cells, have been identified as being responsible for heritable PAH. Indeed, the disease is characterized by excessive cellular proliferation and resistance to apoptosis of smooth muscle and endothelial cells. Significant gene dysregulation at the transcriptional and signaling level has been identified. MicroRNAs are small non-coding RNA molecules that negatively regulate gene expression and have the ability to target numerous genes, therefore potentially controlling a host of gene regulatory and signaling pathways. The major role of miRNAs in pulmonary arterial remodeling is still relatively unknown although research data is emerging apace. Modulation of miRNAs represents a possible therapeutic target for altering the remodeling phenotype in the pulmonary vasculature. This review will focus on the role of miRNAs in regulating smooth muscle and endothelial cell phenotypes and their influence on pulmonary remodeling in the setting of PAH.

Persistent pulmonary hypertension of the newborn: recent advances in pathophysiology and treatment

OBJECTIVES

Although recognized for decades, little is known about the etiology, physiopathology, and prevention of persistent pulmonary hypertension of the newborn (PPHN), and its treatment remains a major challenge for neonatologists. In this review, the clinical features and physiopathology of the syndrome will be addressed, as well as its general and specific treatments.

DATA SOURCE

A review was carried out in PubMed, Cochrane Library, and MRei consult databases, searching for articles related to the syndrome and published between 1995 and 2011.

DATA SYNTHESIS

Risk factors and the physiopathological mechanisms of the syndrome are discussed. The clinical presentation depends on the different factors involved. These are related to the etiology and physiopathology of the different forms of the disease. In addition to the measures used to allow for the decrease in pulmonary vascular resistance after birth, in some instances pulmonary vasodilators will be required. Although inhaled nitric oxide has proved effective, other vasodilators have been recently used, but clinical evidence is still lacking to demonstrate their benefits in the treatment of PPHN.

CONCLUSIONS

Despite recent technological advances and new physiopathological knowledge of this disease, mortality associated with PPHN remains at 10%. More clinical research and evidence-based experimental results are needed to prevent, treat, and reduce the morbidity/mortality associated with this neonatal syndrome.

Expression and significance of α-SMA and PCNA in the vascular adventitia of balloon-injured rat aorta

The aim of this study was to investigate changes in the expression of α-smooth muscle actin (α-SMA) and proliferating cell nuclear antigen (PCNA) in the vascular adventitia of balloon-injured rat aortas in the second and sixth postoperative weeks. A total of 32 rats were divided into a control group and a balloon-injured group. The rats underwent vascular morphometric analysis and adventitial cell counting, as well as immunohistochemical staining of α-SMA and PCNA in postoperative weeks 2 and 6 for observation of the expression of each immune parameter in the vascular adventitia and calculation of the number of PCNA-positive nuclei and the PCNA labeling index (PCNALI) in the vascular adventitia. The area and thickness of the adventitia, the number of nuclei and the PCNALI of the vascular adventitia were significantly increased in the injured group compared with the control group (P<0.05), while the external elastic lamina area (EELA), internal elastic lamina area (IELA) and lumen area (LA) were significantly decreased (P<0.05) in the second week. The area and thickness of the adventitia, the number of nuclei and the PCNALI of the vascular adventitia were significantly increased in the injured group compared with the control group (P<0.05), while the EELA, IELA and LA were significantly reduced (P<0.05) in the sixth week, and were significantly lower than those in the injured group in the second week (P<0.05). The positive expression levels of α-SMA and PCNA in the vascular adventitia were significantly reduced compared with those in the second week after injury. The vascular adventitial cells underwent proliferation and phenotypic switching and participated in vascular remodeling and vascular restenosis following balloon-induced injury. The vascular contractile remodeling in the injured group was more evident in the sixth week than in the second week, followed by a more aggravated vascular stenosis. Consequently, the vascular remodeling was one of the causes of vascular restenosis.

Vinorelbine inhibits angiogenesis and 95D migration via reducing hypoxic fibroblast stromal cell-derived factor 1 secretion

Tumor stroma plays a prominent role in cancer progression. Fibroblasts constitute a majority of the stromal cells in tumor, and yet the functional contributions of these cells to tumor angiogenesis and invasion are poorly understood, especially the anticancer drug interference to these processes. To estimate the effects of vinorelbine (VNR) on fibroblast-associated tumor invasion and angiogenesis, we evaluated the response of 95D and human umbilical vein endothelial cell (HUVEC) migration, tube formation in vitro, as well as capillary formation of rat thoracic aorta rings to hypoxic MRC-5 conditioned medium (CM) by VNR pretreatment. Our results demonstrated that VNR significantly inhibited 95D and HUVEC migration and angiogenesis induced by hypoxic MRC-5 cells. We also showed that hypoxic MRC-5 CM (Hypo-CM) had a higher level of stromal cell-derived factor 1 (SDF-1) secretion, while Hypo-CM up-regulated the CXCR4 expression in HUVECs and 95Ds. This increased activity of SDF-1/CXCR4 paracrine was clearly attenuated by VNR pretreatment. It was further found that pretreating HUVECs and 95Ds with AMD3100, a CXCR4 antagonist, markedly reversed the Hypo-CM promoting cell migration and angiogenesis, while adding exogenous SDF-1 attenuated the inhibition effects of CM collected from VNR-pretreated hypoxic MRC-5 (Hypo-CMV). These data indicate that VNR indirectly decreased 95D migration and angiogenesis through its effect on hypoxic MRC-5, via impacting SDF-1/CXCR4 paracrine, suggesting that VNR could interrupt the influence of fibroblasts on HUVECs and 95Ds to exert an anticancer role. Therefore, fibroblasts should be taken into consideration when evaluating and developing anticancer drugs.

Osteopontin is an endogenous modulator of the constitutively activated phenotype of pulmonary adventitial fibroblasts in hypoxic pulmonary hypertension

Increased cell proliferation and migration, of several cell types are key components of vascular remodeling observed in pulmonary hypertension (PH). Our previous data demonstrate that adventitial fibroblasts isolated from pulmonary arteries of chronically hypoxic hypertensive calves (termed PH-Fibs) exhibit a "constitutively activated" phenotype characterized by high proliferative and migratory potential. Osteopontin (OPN) has been shown to promote several cellular activities including growth and migration in cancer cells. We thus tested the hypothesis that elevated OPN expression confers the "activated" highly proproliferative and promigratory/invasive phenotype of PH-Fibs. Our results demonstrate that, both in vivo and ex vivo, PH-Fibs exhibited increased expression of OPN, as well as its cognate receptors, α(V)β(3) and CD44, compared with control fibroblasts (CO-Fibs). Augmented OPN expression in PH-Fibs corresponded to their high proliferative, migratory, and invasive properties and constitutive activation of ERK1/2 and AKT signaling. OPN silencing via small interfering RNA or sequestering OPN production by specific antibodies led to decreased proliferation, migration, invasion, and attenuated ERK1/2, AKT phosphorylation in PH-Fibs. Furthermore, increasing OPN levels in CO-Fibs via recombinant OPN resulted in significant increases in their proliferative, migratory, and invasive capabilities to the levels resembling those of PH-Fibs. Thus our data suggest OPN as an essential contributor to the activated (highly proliferative, migratory, and proinvasive) phenotype of pulmonary adventitial fibroblasts in hypoxic PH.