Primary pulmonary hypertension. Vascular structure, morphometry, and responsiveness to vasodilator agents

Dysregulated VEGF/VEGFR-2 Signaling and Plexogenic Lesions in the Embryonic Lungs of Chickens Predisposed to Pulmonary Arterial Hypertension

Plexiform lesions are a hallmark of pulmonary arterial hypertension (PAH) in humans and are proposed to stem from dysfunctional angioblasts. Broiler chickens (Gallus gallus) are highly susceptible to PAH, with plexiform-like lesions observed in newly hatched individuals. Here, we reported the emergence of plexiform-like lesions in the embryonic lungs of broiler chickens. Lung samples were collected from broiler chickens at embryonic day 20 (E20), hatch, and one-day-old, with PAH-resistant layer chickens as controls. Plexiform lesions consisting of CD133+/vascular endothelial growth factor receptor type-2 (VEGFR-2)+ angioblasts were exclusively observed in broiler embryos and sporadically in layer embryos. Distinct gene profiles of angiogenic factors were observed between the two strains, with impaired VEGF-A/VEGFR-2 signaling correlating with lesion development and reduced arteriogenesis. Pharmaceutical inhibition of VEGFR-2 resulted in enhanced lesion development in layer embryos. Moreover, broiler embryonic lungs displayed increased activation of HIF-1α and nuclear factor erythroid 2-related factor 2 (Nrf2), indicating a hypoxic state. Remarkably, we found a negative correlation between lung Nrf2 activation and VEGF-A and VEGFR-2 expression. In vitro studies indicated that Nrf2 overactivation restricted VEGF signaling in endothelial progenitor cells. The findings from broiler embryos suggest an association between plexiform lesion development and impaired VEGF system due to aberrant activation of Nrf2.

Case report: Pathological differences in pulmonary arterial hypertension in long-term responders to calcium channel blockers

Background

This study investigates the pulmonary arterial histopathology in patients with idiopathic pulmonary arterial hypertension (IPAH) and acute vasoreactive phenotype, who demonstrated long-term survival (>30 years) and incidental death from causes other than PAH progression. The pathological changes observed in these patients were compared with those in patients with bone morphogenetic protein receptor type 2 (BMPR2) mutation.

Case Presentation

We present two cases of patients with pulmonary arterial hypertension (PAH) who died incidentally from causes unrelated to PAH progression. We report compares pulmonary arterial histopathology in long-term survivors of CCB-responsive PAH patient and a hereditary PAH patient with a BMPR2 mutation. Lung specimens were analyzed using the Heath and Edwards (HE) classification and percentage muscular wall thickness (%MWT) of pulmonary arterioles. A significant difference in the severity of grading (p = 0.0001) and distribution between grades 1-2, 4 (p = 0.001), and 5 (p = 0.014) was observed between both patients. These findings suggest differential vascular pathology between the two cases, with CCB responders displaying more mild illness lesions compared to BMPR2 mutant patients.

Conclusion

The study revealed that CCB responders exhibit more mild illness vascular lesions than BMPR2 mutant patients despite their long-term survival, suggesting a difference in vascular pathology between the two phenotypes.

Potential contribution of early endothelial progenitor cell (eEPC)-to-macrophage switching in the development of pulmonary plexogenic lesion

Background

Plexiform lesions, which have a dynamic appearance in structure and cellular composition, are the histological hallmark of severe pulmonary arterial hypertension in humans. The pathogenesis of the lesion development remains largely unknown, although it may be related to local inflammation and dysfunction in early progenitor endothelial cells (eEPCs). We tested the hypothesis that eEPCs contribute to the development of plexiform lesions by differentiating into macrophages in the setting of chronic inflammation.

Methods

The eEPC markers CD133 and VEGFR-2, macrophage lineage marker mannose receptor C-type 1 (MRC1), TNFα and nuclear factor erythroid 2-related factor 2 (Nrf2) in plexiform lesions in a broiler model were determined by immunohistochemistry. eEPCs derived from peripheral blood mononuclear cells were exposed to TNFα, and macrophage differentiation and angiogenic capacity of the cells were evaluated by phagocytotic and Matrigel plug assays, respectively. The role of Nrf2 in eEPC-to-macrophage transition as well as in MRC1 expression was also evaluated. Intratracheal installation of TNFα was conducted to determine the effect of local inflammation on the formation of plexiform lesions.

Results

Cells composed of the early lesions have a typical eEPC phenotype whereas those in more mature lesions display molecular and morphological characteristics of macrophages. Increased TNFα production in plexiform lesions was observed with lesion progression. In vitro studies showed that chronic TNFα challenge directed eEPCs to macrophage differentiation accompanied by hyperactivation of Nrf2, a stress-responsive transcription factor. Nrf2 activation (Keap1 knockdown) caused a marked downregulation in CD133 but upregulation in MRC1 mRNA. Dual luciferase reporter assay demonstrated that Nrf2 binds to the promoter of MRC1 to trigger its expression. In good agreement with the in vitro observation, TNFα exposure induced macrophage differentiation of eEPCs in Matrigel plugs, resulting in reduced neovascularization of the plugs. Intratracheal installation of TNFα resulted in a significant increase in plexiform lesion density.

Conclusions

This work provides evidence suggesting that macrophage differentiation of eEPCs resulting from chronic inflammatory stimulation contributes to the development of plexiform lesions. Given the key role of Nrf2 in the phenotypic switching of eEPCs to macrophages, targeting this molecular might be beneficial for intervention of plexiform lesions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02210-7.

The physiologic basis of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare dyspnea-fatigue syndrome caused by a progressive increase in pulmonary vascular resistance (PVR) and eventual right ventricular (RV) failure. In spite of extensive pulmonary vascular remodeling, lung function in PAH is generally well preserved, with hyperventilation and increased physiologic dead space, but minimal changes in lung mechanics and only mild to moderate hypoxemia and hypocapnia. Hypoxemia is mainly caused by a low mixed venous PO₂ from a decreased cardiac output. Hypocapnia is mainly caused by an increased chemosensitivity. Exercise limitation in PAH is cardiovascular rather than ventilatory or muscular. The extent of pulmonary vascular disease in PAH is defined by multipoint pulmonary vascular pressure-flow relationships with a correction for hematocrit. Pulsatile pulmonary vascular pressure-flow relationships in PAH allow for the assessment of RV hydraulic load. This analysis is possible either in the frequency-domain or in the time-domain. The RV in PAH adapts to increased afterload by an increased contractility to preserve its coupling to the pulmonary circulation. When this homeometric mechanism is exhausted, the RV dilates to preserve flow output by an additional heterometric mechanism. Right heart failure is then diagnosed by imaging of increased right heart dimensions and clinical systemic congestion signs and symptoms. The coupling of the RV to the pulmonary circulation is assessed by the ratio of end-systolic to arterial elastances, but these measurements are difficult. Simplified estimates of RV-PA coupling can be obtained by magnetic resonance or echocardiographic imaging of ejection fraction.

Electrical Stimulation-Guided Approach to Pulmonary Artery Catheter Ablation in Patients with Idiopathic Pulmonary Arterial Hypertension: A Pilot Feasibility Study with a 12-Month Follow-Up

Background

Recently, transcatheter pulmonary artery (PA) ablation aiming at sympathetic denervation has been proposed in pulmonary arterial hypertension (PAH). This pilot feasibility study aimed to assess the feasibility of selective radiofrequency PA ablation based on response to high-frequency stimulation mapping.

Methods

The study comprised 3 female patients with idiopathic PAH (IPAH). The following reactions to PA stimulation were noted and marked by color points on the three-dimensional map: sinus bradycardia (heart rate decrease ≥15%), tachycardia (heart rate increase ≥15%), phrenic nerve capture, and cough. Since the most appropriate ablation strategy was unknown, two approaches were suggested, according to stimulation results: ablation at points with any heart rate response (either bradycardia or tachycardia)—this approach was applied in patient #1 (IPAH long-term responder to calcium channel blockers); segmental ablation at points with no response and with tachycardia response (one IPAH long-term responder to calcium channel blockers patient and one–IPAH with negative vasoreactive testing). Hemodynamic measurements were performed before and after denervation. Follow-up visits were scheduled at 6 and 12 months.

Results

Six-months follow-up was uneventful for patients #1 and 3; patient #2 had one syncope and reduced 6-minute walk test distance and peak VO₂ consumption. At 12 months, there was a normalization of mean PA pressure and pulmonary vascular resistance (PVR) in patient #1. Patient #2 had no change in PA pressure and PVR at 12 months. Patient #3 remained in II functional class; however, there was an increase in mean PA pressure and loss of vasoreactivity.

Conclusions

Electrical high-frequency stimulation of the PA identifies several types of evoked reactions: heart rate slowing, acceleration, phrenic nerve capture, and cough. The improvement in clinical and hemodynamic parameters following targeted PA ablation in the IPAH patient with positive vasoreactive testing should be confirmed in larger studies.

Pathological abnormalities in splenic vasculature in non-cirrhotic portal hypertension: Its relevance in the management of portal hypertension

BACKGROUND

Portal hypertension (PH) is associated with changes in vascular structure and function of the portosplenomesenteric system (PSMS). This is referred to as portal hypertensive vasculopathy. Pathological abnormalities of PSMS has been described in the literature for cirrhotic patients. Raised portal pressure and hyperdynamic circulation are thought to be the underlying cause of this vasculopathy. In view of this, it is expected that pathological changes in splenic and portal vein similar to those reported in cirrhotic patients with PH may also be present in patients with non-cirrhotic PH (NCPH).

AIM

To investigate pathological abnormalities of splenic vein in patients with NCPH, and suggest its possible implications in the management of PH.

METHODS

A prospective observational study was performed on 116 patients with NCPH [Extrahepatic portal vein obstruction (EHPVO): 53 and non-cirrhotic portal fibrosis (NCPF): 63] who underwent proximal splenorenal shunt (PSRS), interposition shunt or splenectomy with devascularization in JIPMER, Pondicherry, India, a tertiary level referral center, between 2011-2016. All patients were evaluated by Doppler study of PSMS, computed tomography porto-venogram and upper gastrointestinal endoscopy. An acoustic resonance forced impulse (ARFI) scan and abdomen ultrasound were done for all cases to exclude cirrhosis. Intraoperative and histopathological assessment of the harvested splenic vein was performed in all. The study group was divided into delayed and early presentation based on the median duration of symptoms (i.e. 108 mo).

RESULTS

The study group comprising of 116 patients [77 (66%) females and 39 (34%) males] with NCPH had a median age of 22 years. Median duration of symptoms was 108 mo. The most common presentation in both EHPVO and NCPF patients was upper gastrointestinal bleeding (hematemesis and melena). The ARFI scan revealed a median score of 1.2 (1.0-1.8) m/s for EHPVO and 1.5 (0.9-2.8) m/s for NCPF. PSRS was performed in 84 patients (two of whom underwent interposition PSRS using a 10 mm Dacron graft); splenoadrenal shunt in 9; interposition mesocaval shunt in 5; interposition 1^st jejunal to caval shunt in 1 patient and devascularization with splenectomy in 17 patients. Median pre-splenectomy portal pressure was 25 (range: 15-51) mm Hg. In 77% cases, the splenic vein was abnormal upon intraoperative assessment. Under macroscopic examination, wall thickening was observed in 108 (93%), venous thrombosis in 32 (28%) and vein wall calcification in 27 (23%) cases. Upon examination under a surgical magnification loupe, 21 (18%) patients had intimal defects in the splenic vein. Histopathological examination of veins was abnormal in all cases. Medial hypertrophy was noted in nearly all patients (107/116), while intimal fibrosis was seen in 30%. Ninety one percent of patients with intimal fibrosis also had venous thrombosis. Vein wall calcification was found in 22%, all of whom had intimal fibrosis and venous thrombosis. The proportion of patients with pathological abnormalities in the splenic vein were significantly greater in the delayed presentation group as compared to the early presentation group.

CONCLUSION

Pathological changes in the splenic vein similar to those in cirrhotic patients with PH are noted in NCPH. We recommend that PH in NCPH be treated as systemic and pulmonary hypertension equivalent in the gastrointestinal tract, and that early aggressive therapy be initiated to reduce portal pressure and hemodynamic stress to avoid potential lethal effects.

Pulmonary hypertension on systemic sclerosis-lupus erythematosus overlap syndrome

PURPOSE

There are authentic observations of combination of systemic lupus erythematosus (SLE) with systemic sclerosis (SS) and with polymyositis defined as overlap syndromes. The prevalence of pulmonary hypertension is unknown in SS-SLE overlap syndrome because of its rarity. The aim of our study was to precise clinical, paraclinical and evolutive features of pulmonary hypertension in patients with systemic sclerosis-systemic lupus erythematosus (SS-SLE) overlap syndrome.

METHODS

Sixteen cases of SS-SLE overlap syndrome were retrospectively studied in a period of 16 years (2000-2015). SS-SLE overlap syndrome was diagnosed in the presence of at least 4 criteria of the American College of Rheumatology (ACR) for the diagnosis of SLE and a major criterion or 2 minor criteria of ACR of SS classification. Pulmonary arterial pressure (PAP) was estimated with doppler echocardiography. Pulmonary hypertension (PAH) was defined by a PAP superior than 30mmHg. We distributed groups according to the existence (Group 1) or not (Group 2) of a PAH. Epidemiological, clinical and evolutive features were compared between the two groups with bilateral fisher test (P significant if inferior at 0.05) RESULTS: Sixteen cases of female patients with SS-SLE overlap syndrome with a middle-age of 39 years, extreme (29-58 years) were studied. PAH complicated the evolution of SS-SLE overlap syndrome in six cases with a middle-age of 41 years. Ten patients of the group 2 had an average age of 40 years. The average age of the beginning of the disease was 28 years in the group 1 and 31 years in the group 2. SS preceded SLE in 6 among 16 cases (Group 1: 2/6, Group 2: 4/10). SS was revealed most frequently by Raynauw's Syndrome in both groups (Group 1: 4/6, Group 2: 7/10). Cutaneous and articular involvements were the most frequent observed manifestations of SLE (Group 1: 5/6, Group 2: 6/10). In the group 1, the PAH was discovered approximatively11 years after the beginning of the SS-SLE overlap syndrome. The average PAP was 52mmHg, extreme (32-80mmHg). A right cardiac insufficiency complicated the evolution of the PAH in 3 cases. The PAH was primitive in 3 cases. There was no significant difference concerning the SS-SLE overlap syndrome onset disease symptoms, the frequency of lung involvement and esophageal, neurological, articular and trophic manifestations. PAH was not associated with lupic proliferative renal disease, neither with cutaneous proximal sclerosis nor with anti-Scl70 positivity. Patients were treated with vasodilator treatment in eleven cases: prostacyclin derivates in five cases and endothelin receptor antagonist in six cases. Two patients received corticosteroids and boli of cyclophosphamide for renal involvement and neurologic involvement in each case. Stabilization of PAP was observed in these two cases. Mean follow-up disease was 67 months, extreme (4-124 months) Cutaneous sclerosis evolution was not significantly different between both groups. Global cardiac insufficiency secondary to PAH caused death in one case.

CONCLUSION

According to the results of our study, SS-SLE overlap syndrome complicated with PAH seems to be associated more frequently with limited and distal cutaneous manifestations. Patients that have developed lupus nephropathy and/or had positive anti-Scl70 seem to be protected from appearance of PAH during the SS-SLE overlap syndrome.

Combined Spinal and Epidural Anaesthesia for Caesarean Section in a Parturient with Severe Primary Pulmonary Hypertension

We describe the management of a parturient with severe primary pulmonary hypertension who underwent caesarean section. A multi-disciplinary approach was used. She was admitted to the intensive care unit perioperatively for invasive monitoring and trial of inhaled nitric oxide. Anaesthesia was provided by combined spinal-epidural block. We discuss controversies about the management of obstetric patients with this rare and serious condition.

Vascular narrowing in pulmonary arterial hypertension is heterogeneous: rethinking resistance

In idiopathic pulmonary arterial hypertension (PAH), increased pulmonary vascular resistance is associated with structural narrowing of small (resistance) vessels and increased vascular tone. Current information on pulmonary vascular remodeling is mostly limited to averaged increases in wall thickness, but information on number of vessels affected and internal diameter decreases for vessels of different sizes is limited. Our aim was to quantify numbers of affected vessels and their internal diameter decrease for differently sized vessels in PAH in comparison with non‐PAH patients. Internal and external diameters of transversally cut vessels were measured in five control subjects and six PAH patients. Resistance vessels were classified in Strahler orders, internal diameters 13 μm (order 1) to 500 μm (order 8). The number fraction, that is, percentage of affected vessels, and the internal diameter fraction, that is, percentage diameter of normal diameter, were calculated. In PAH, not all resistance vessels are affected. The number fraction is about 30%, that is, 70% of vessels have diameters not different from vessels of control subjects. Within each order, the decrease in diameter of affected vessels is variable with an averaged diameter fraction of 50–70%. Narrowing of resistance vessels is heterogeneous: not all vessels are narrowed, and the decrease in internal diameters, even within a single order, vary largely. This heterogeneous narrowing alone cannot explain the large resistance increase in PAH. We suggest that rarefaction could be an important contributor to the hemodynamic changes.

Involvement of endothelial progenitor cells in the formation of plexiform lesions in broiler chickens: possible role of local immune/inflammatory response

Plexiform lesions (PLs), which are often accompanied by perivascular infiltrates of mononuclear cells, represent the hallmark lesions of pulmonary arteries in humans suffering from severe pulmonary arterial hypertension (PAH). Endothelial progenitor cells (EPCs) have been recently implicated in the formation of PLs in human patients. PLs rarely develop in rodent animal models of PAH but can develop spontaneously in broiler chickens. The aim of the present study was to confirm the presence of EPCs in the PLs in broilers. The immune mechanisms involved in EPC dysfunction were also evaluated. Lungs were collected from commercial broilers at 1 to 4 weeks of age. The right/total ventricle ratios indicated normal pulmonary arterial pressures for all sampled birds. Immunohistochemistry was performed to determine the expressions of EPC markers (CD133 and VEGFR-2) and proangiogenic molecule hepatocyte growth factor (HGF) in the lung samples. An EPC/lymphocyte co-culture system was used to investigate the functional changes of EPCs under the challenge of immune cells. PLs with different cellular composition were detected in the lungs of broilers regardless of age, and they were commonly surrounded by moderate to dense perivascular mononuclear cell infiltrates. Immunohistochemical analyses revealed the presence of CD133⁺ and VEGFR-2⁺ cells in PLs. These structures also exhibited a strong expression of HGF. Lymphocyte co-culture enhanced EPC apoptosis and completely blocked HGF-stimulated EPC survival and in vitro tube formation. Taken together, this work provides evidence for the involvement of EPCs in the development of PLs in broilers. It is suggested that the local immune cell infiltrate might serve as a contributor to EPC dysfunction by inducing EPC death and limiting their response to angiogenic stimuli. Broiler chickens may be valuable for investigating reversibility of plexogenic arteriopathy using gene-modified inflammation-resistant EPCs.

Vasodilator responsiveness in idiopathic pulmonary arterial hypertension: identifying a distinct phenotype with distinct physiology and distinct prognosis

Within the cohort of patients suffering from idiopathic pulmonary arterial hypertension (IPAH) is a group that responds dramatically (VR-PAH) to an acute vasodilator challenge and that has excellent long-term hemodynamic improvement and prognosis on high dose calcium channel blockers compared with vasodilator non-responders (VN-PAH). For the purposes of diagnosing VR-PAH, there is to date no test to replace the acute vasodilator challenge. However, recent studies have identified markers that may aid in the identification of VR-PAH, including peripheral blood lymphocyte RNA expression levels of desmogelin-2 and Ras homolog gene family member Q, and plasma levels of provirus integration site for Moloney murine leukemia virus. Genome wide-array studies of peripheral blood DNA have demonstrated differences in disease specific genetic variants between VR-PAH and NR-PAH, with particular convergence on cytoskeletal function pathways and Wnt signaling pathways. These studies offer hope for future non-invasive identification of VR-PAH, and insights into pathogenesis that may lead to novel therapies. Examination of the degree of pulmonary microvascular perfusion in PAH has offered additional insights. During the acute vasodilator challenge, VR-PAH patients demonstrate true vasodilation with recruitment and increased perfusion of the capillary bed, while VN-PAH patients are unable to recruit vasculature. In the very few reports of lung histology, VR-PAH has more medial thickening in the precapillary arterioles, while VN-PAH has the classic histology of PAH, including intimal thickening. VR-PAH is a disorder with a phenotype distinct from VN-PAH and other types of PAH, and should be considered separately in the classification of PAH.

Optical coherence tomography evaluation of pulmonary arterial vasculopathy in Systemic Sclerosis

Our current understanding of the pathophysiology of pulmonary vascular disease is incomplete, since information about alterations of the pulmonary vasculature in pulmonary arterial hypertension (PAH) is primarily provided by autopsy or tissue specimens. The aim of this study was to compare the distal pulmonary vasculature of <2 mm in diameter in Systemic Sclerosis (SSc) patients with (n = 17) and without (n = 5) associated PAH using Optical Coherence Tomography during Right Heart catheterization. SSc-PAH patients showed significant thickening of Intima Media Thickening Area compared to patients without PAH (27 +/− 5.8% vs. 21 +/− 1.4%, p = 0.024). A good haemodynamic response to previous targeted PAH treatment was associated with a significantly greater number of small pulmonary artery side branches <300 μm per cm vessel (3.8 +/− 1.1 vs. 1.8 +/− 1.1; p = 0.010) and not associated with Intima Media thickening Area (26 +/− 5.4% vs. 28 +/− 6.7%; p = 0.6). Unexpected evidence of pulmonary artery thrombus formation was found in 19% of SSc-PAH patients. This is the first in-vivo study demonstrating a direct link between a structural abnormality of pulmonary arteries and a response to targeted treatment in PAH. Intravascular imaging may identify subgroups that may benefit from anticoagulation.

Pulmonary vascular remodeling in pulmonary hypertension

Pulmonary vascular remodeling is the key structural alteration in pulmonary hypertension and involves changes in the intima, media and adventitia, often with the interplay of inflammatory cells. This review examines the pathology of these changes and highlights some of the pathogenetic mechanisms that underlie the remodeling process.

Endothelial hyperpermeability in severe pulmonary arterial hypertension: role of store-operated calcium entry

Here, we tested the hypothesis that animals with severe pulmonary arterial hypertension (PAH) display increased sensitivity to vascular permeability induced by activation of store-operated calcium entry. To test this hypothesis, wild-type and transient receptor potential channel 4 (TRPC4) knockout Fischer 344 rats were given a single injection of Semaxanib (SU5416; 20 mg/kg) followed by 3 wk of exposure to hypoxia (10% oxygen) and a return to normoxia (21% oxygen) for an additional 2-3 wk. This Semaxanib/hypoxia/normoxia (i.e., SU5416/hypoxia/normoxia) treatment caused PAH, as evidenced by development of right ventricular hypertrophy, pulmonary artery medial hypertrophy, and occlusive lesions within precapillary arterioles. Pulmonary artery pressure was increased fivefold in Semaxanib/hypoxia/normoxia-treated animals compared with untreated, Semaxanib-treated, and hypoxia-treated controls, determined by isolated perfused lung studies. Thapsigargin induced a dose-dependent increase in permeability that was dependent on TRPC4 in the normotensive perfused lung. This increase in permeability was accentuated in PAH lungs but not in Semaxanib- or hypoxia-treated lungs. Fluid accumulated in large perivascular cuffs, and although alveolar fluid accumulation was not seen in histological sections, Evans blue dye conjugated to albumin was present in bronchoalveolar lavage fluid of hypertensive but not normotensive lungs. Thus PAH is accompanied by a TRPC4-dependent increase in the sensitivity to edemagenic agents that activate store-operated calcium entry.

CCN1 suppresses pulmonary vascular smooth muscle contraction in response to hypoxia

Pulmonary vasoconstriction and increased vascular resistance are common features in pulmonary hypertension (PH). One of the contributing factors in the development of pulmonary vasoconstriction is increased pulmonary artery smooth muscle cell (PASMC) contraction. Here we report that CCN1, an extracellular matrix molecule, suppressed PASMC contraction in response to hypoxia. CCN1 (Cyr61), discovered in past decade, belongs to the Cyr61-CTGF-Nov (CCN) family. It carries a variety of cellular functions, including angiogenesis and cell adhesion, death, and proliferation. Hypoxia robustly upregulated the expression of CCN1 in the pulmonary vessels and lung parenchyma. Given that CCN1 is a secreted protein and functions in a paracine manner, we examined the potential effects of CCN1 on the adjacent smooth muscle cells. Interestingly, bioactive recombinant CCN1 significantly suppressed hypoxia-induced contraction in human PASMCs in vitro. Consistently, in the in vivo functional studies, administration of bioactive CCN1 protein significantly decreased right ventricular pressure in three different PH animal models. Mechanistically, protein kinase A-pathway inhibitors abolished the effects of CCN1 in suppressing PASMC contraction. Furthermore, CCN1-inhibited smooth muscle contraction was independent of the known vasodilators, such as nitric oxide. Taken together, our studies indicated a novel cellular function of CCN1, potentially regulating the pathogenesis of PH.

The sexual dimorphism associated with pulmonary hypertension corresponds to a fibrotic phenotype

Although female predominance in the development of all types of pulmonary hypertension (PH) is well established, many clinical studies have confirmed that females have better prognosis and higher survival rate than males. There is no clear explanation of why sex influences the pathogenesis and progression of PH. Using a rat angioproliferative model of PH, which closely resembles the primary pathological changes observed in humans, we evaluated the role of sex in the development and progression of PH. Female rats had a more pronounced increase in medial thickness in the small pulmonary arteries. However, the infiltration of small pulmonary arteries by inflammatory cells was found only in male rats, and this corresponded to increased myeloperoxidase activity and abundant adventitial and medial fibrosis that were not present in female rats. Although the level of right ventricle (RV) peak systolic pressure was similar in both groups, the survival rate in male rats was significantly lower. Moreover, male rats presented with a more pronounced increase in RV thickness that correlated with diffuse RV fibrosis and significantly impaired right cardiac function. The reduction in fibrosis in female rats correlated with increased expression of caveolin-1 and reduced endothelial nitric oxide synthase-derived superoxide. We conclude that, in the pathogenesis of PH, female sex is associated with greater remodeling of the pulmonary arteries but greater survival. Conversely, in males, the development of pulmonary and cardiac fibrosis leads to early and severe RV failure, and this may be an important reason for the lower survival rate among males.

RETRACTED ARTICLE: High Pulsatility Flow Promotes Vascular Fibrosis by Triggering Endothelial EndMT and Fibroblast Activation

Vascular fibrosis, the formation of excess fibrous tissue on the blood vessel wall, is characterized by unmitigated proliferation of fibroblasts or myofibroblast-like cells exhibiting α-smooth-muscle-actin in vessel lumen and other vascular layers. It likely contributes to vascular unresponsiveness to conventional therapies. This paper demonstrates a new flow-induced vascular fibrosis mechanism. Using our developed flow system which simulates the effect of vessel stiffening and generates unidirectional high pulsatility flow (HPF) with the mean shear flow at a physiological level, we have shown that HPF caused vascular endothelial dysfunction. Herein, we further explored the role of HPF in vascular fibrosis through endothelial-to-mesenchymal transdifferentiation (EndMT). Pulmonary arterial endothelial cells (ECs) were exposed to steady flow and HPF, which have the same physiological mean fluid shear but different in flow pulsatility. Cells were analyzed after being conditioned with flows for 24 or 48 h. HPF was found to induce EndMT of cells after 48 h stimulation; cells demonstrated drastically decreased expression in EC marker CD31, as well as increased transforming growth factor β, α-SMA, and collagen type-I, in both gene and protein expression profiles. Using the flow media from HPF-conditioned endothelial culture to cultivate arterial adventitial fibroblasts (AdvFBs) and ECs respectively, we found that the conditioned media respectively enhanced migration, proliferation and α-SMA expression of AdvFBs, and induced EndMT of ECs. It was further revealed that cells exposed to HPF exhibited much higher percentage of caspase-positive cells compared to those exposed to steady flow. Apoptotic cells together with remaining, caspase-negative cells suggested the presence of apoptosis-resistant dysfunctional ECs which likely underwent EndMT process and perpetuated fibrosis throughout vascular tissues. Therefore, our results indicate that prolonged HPF stimuli induce vascular fibrosis through triggering EndMT and EC-mediated AdvFB activation and migration, which follows initial endothelial inflammation, dysfunction and apoptosis.

The role of calcium channel blockers for the treatment of pulmonary arterial hypertension: How much do we actually know and how could they be positioned today?

Calcium channel blockers (CCB) were the first vasodilator agents to gain popular acceptance in the treatment of pulmonary arterial hypertension (PAH). They have been shown to be particularly effective in patients who show a significant immediate hemodynamic response to pulmonary vasodilators ("responders"). The application of CCB is currently restricted to "responders" only. It is believed that no more than 5% of PAH patients will benefit from CCB long term. The response rate of most non-idiopathic forms of PAH is considered to be even lower. The "non-responders" as well as "responders" who fail to benefit from CCB should be treated with newer agents, collectively called "advanced PAH therapy." The basis of this consensus rests on empiric experience gained in the PAH community over the years. However, the cut-points where advanced agents are more effective than CCB and where there is no additional role for CCB remain unknown. In this manuscript, we review the data concerning this issue and postulate a role for CCB in the modern era of pulmonary hypertension therapy.

Phosphodiesterase 5 inhibitors augment UT-15C-stimulated ATP release from erythrocytes of humans with pulmonary arterial hypertension

Both prostacyclin analogs and phosphodiesterase 5 (PDE5) inhibitors are effective treatments for pulmonary arterial hypertension (PAH). In addition to direct effects on vascular smooth muscle, prostacyclin analogs increase cAMP levels and ATP release from healthy human erythrocytes. We hypothesized that UT-15C, an orally available form of the prostacyclin analog, treprostinil, would stimulate ATP release from erythrocytes of humans with PAH and that this release would be augmented by PDE5 inhibitors. Erythrocytes were isolated and the effect of UT-15C on cAMP levels and ATP release were measured in the presence and absence of the PDE5 inhibitors, zaprinast or tadalafil. In addition, the ability of a soluble guanylyl cyclase inhibitor to prevent the effects of tadalafil was determined. Erythrocytes of healthy humans and humans with PAH respond to UT-15C with increases in cAMP levels and ATP release. In both groups, UT-15C-induced ATP release was potentiated by zaprinast and tadalafil. The effect of tadalafil was prevented by pre-treatment with an inhibitor of soluble guanylyl cyclase in healthy human erythrocytes. Importantly, UT-15C-induced ATP release was greater in PAH erythrocytes than in healthy human erythrocytes in both the presence and the absence of PDE5 inhibitors. The finding that prostacyclin analogs and PDE5 inhibitors work synergistically to enhance release of the potent vasodilator ATP from PAH erythrocytes provides a new rationale for the co-administration of these drugs in this disease. Moreover, these results suggest that the erythrocyte is a novel target for future drug development for the treatment of PAH.

The current approach into signaling pathways in pulmonary arterial hypertension and their implication in novel therapeutic strategies

Many mediators and signaling pathways, with their downstream effectors, have been implicated in the pathogenesis of pulmonary hypertension. Currently approved drugs, representing an option of specific therapy, target NO, prostacyclin or ET-1 pathways and provide a significant improvement in the symptomatic status of patients and a slower rate of clinical deterioration. However, despite such improvements in the treatment, PAH remains a chronic disease without a cure, the mortality associated with PAH remains high and effective therapeutic regimens are still required. Knowledge about the role of the pathways involved in PAH and their interactions provides a better understanding of the pathogenesis of the disease and may highlight directions for novel therapeutic strategies for PAH. This paper reviews some novel, promising PAH-associated signaling pathways, such as RAAS, RhoA/ROCK, PDGF, PPAR, and TGF, focusing also on their possible interactions with well-established ones such as NO, ET-1 and prostacyclin pathways.

Pulmonary Arterial Hypertension and Insulin Resistance

The clinical recognition of pulmonary arterial hypertension (PAH) is increasing, and with recent therapeutic advances, short-term survival has improved. In spite of these advances, however, PAH remains a disease with substantial morbidity and long-term mortality. The pathogenesis of PAH involves a complex interaction of local and distant cytokines, growth factors, co-factors, and transcription factors occurring in the right genetic and environmental setting. These factors ultimately lead to the detrimental changes in vascular anatomy and function seen in PAH patients. An important association between obesity/insulin resistance and PAH has recently been identified. Both conditions occur in the presence of a chronic low-grade inflammatory state, and although it is unlikely that a single pathway is solely responsible for the observed association, deficiencies in adiponectin, apolipoprotein E (ApoE) and peroxisome proliferator-activator receptor gamma (PPAR-γ) activity likely play a prominent role. Although incompletely understood, it is clear that further investigation is warranted and the role of weight loss and improved glycemic control in the treatment of at-risk patients with PAH and obesity should be determined.

In vivo assessment of pulmonary arterial wall fibrosis by intravascular optical coherence tomography in pulmonary arterial hypertension: a new prognostic marker of adverse clinical follow-up

Background:

The aim is to correlate pulmonary arterial (PA) remodeling estimated by PA fibrosis in PA hypertension (PAH) with clinical follow-up. Histology of PA specimens is also performed.

Methods:

19 patients, aged 54±16 (4 men), functional class II-III were studied with right heart catheterization, PA Intravascular Ultrasound and optical coherence tomography (OCT) in inferior lobe segment. PA wall fibrosis was obtained by OCT ( area of fibrosis/PA cross sectional area × 100). Patients follow-up was blind to OCT. Events were defined as mortality, lung transplantation, need of intravenous prostaglandins or onset of right ventricular failure.

Results:

OCT measurements showed high intra- and interobserver agreement. There was a good correlation between OCT and histology in PA fibrosis from explanted lungs. Area of fibrosis was 1.4±0.8 mm², % fibrosis was 22.3±8. Follow-up was 3.5 years (2.5-4.5). OCT %Fib was significantly correlated with PA capacitance (r=-0.536) and with pulmonary vascular rsistance (r=0.55). Patients were divided according to the median value of PA fibrosis. There were 10 patients with a high (≥ 22%) and 9 with a low fibrosis (<22%). Events occurred in 6 (1 death, 1 lung transplantation, 2 intravenous prostaglandins, 2 right heart failure) out of 10 patients with high and in 0 out of 9 patients with low fibrosis (p<0.01).

Conclusions:

In PAH, the severity of PA remodeling assessed by OCT wall fibrosis was significantly predictive of severely unfavorable clinical outcome. In vivo assessment of pulmonary arterial wall fibrosis by intravascular OCT in PAH is a promising new prognostic marker of adverse clinical outcome.

Cross talk between autophagy and apoptosis in pulmonary hypertension

Endothelial cell (EC) apoptosis and apoptosis resistant proliferation have been proposed to play crucial roles in the development of featured plexiform lesions in the pathogenesis of pulmonary hypertension (PH). Subsequently, EC injury associated smooth muscle cell (SMC) proliferation facilitates vascular remodeling and eventually leads to narrowed vascular lumen, increased pulmonary vascular resistance, increased pulmonary arterial pressure, and right heart failure. The imbalance between cell death and proliferation occurs in every stage of pulmonary vascular remodeling and pathogenesis of PH, and involves every cell type in the vasculature including, but not limited to ECs, SMCs, and fibroblasts. Despite extensive studies, the detailed cellular and molecular mechanisms on how the transition from initial apoptosis of ECs to apoptosis resistant proliferation on ECs and SMCs remains unclear. Recent knowledge on autophagy, a conservative and powerful regulatory machinery existing in almost all mammalian cells, has shed light on the complex and delicate control on cell fate in the development of vascular remodeling in PH. In this review, we will discuss the recent understandings on how the cross-talk between apoptosis and autophagy regulates cell death or proliferation in PH pathogenesis, particularly in pulmonary vascular remodeling involving ECs and SMCs.

Vascular compromise and hemodynamics in pulmonary arterial hypertension: model predictions

A previously validated computer model of the normal pulmonary circulation is adapted to simulate pulmonary arterial hypertension (PAH) in humans. Model predictions are used to explore the suitability of currently accepted criteria for diagnosing PAH by correlating hemodynamic data with the degree of vascular compromise (disease severity). Model predictions demonstrate a hyperbolic relationship between vascular compromise, mean pulmonary artery pressure (PAPm) and pulmonary vascular resistance (PVR). PAPm and PVR change very little from disease initiation until a vascular compromise of 65% to 70% (surface area of 0.35 to 0.3 of baseline, respectively) is reached. Following that, further compromise is associated with a steep rise in PAPm and PVR. The relationship between vascular compromise and hemodynamics may explain the relative stability of cardiac output early in this disease process and, therefore, the lack of symptoms. It also explains the rapid deterioration following diagnosis if the disease remains untreated. Model predictions demonstrate the inadequacy of the current hemodynamic criteria for diagnosing PAH over a wide range of left atrial pressure and cardiac output combinations and for early detection of disease. The model provides an alternative approach to diagnosing PAH by translating hemodynamic data to degree of vascular compromise.

Plexiform lesions in the lungs of domestic fowl selected for susceptibility to pulmonary arterial hypertension: incidence and histology

Plexiform lesions develop in the pulmonary arteries of humans suffering from idiopathic pulmonary arterial hypertension (IPAH). Plexogenic arteriopathy rarely develops in existing animal models of IPAH. In this study, plexiform lesions developed in the lungs of rapidly growing meat-type chickens (broiler chickens) that had been genetically selected for susceptibility to IPAH. Plexiform lesions developed spontaneously in: 42% of females and 40% of males; 35% of right lungs, and 45% of left lungs; and, at 8, 12, 16, 20, 24, and 52 weeks of age the plexiform lesion incidences averaged 52%, 50%, 51%, 40%, 36%, and 22%, respectively. Plexiform lesions formed distal to branch points in muscular interparabronchial pulmonary arteries exhibiting intimal proliferation. Perivascular mononuclear cell infiltrates consistently surrounded the affected arteries. Proliferating intimal cells fully or partially occluded the arterial lumen adjacent to plexiform lesions. Broilers reared in clean stainless steel cages exhibited a 50% lesion incidence that did not differ from the 64% incidence in flock mates grown on dusty floor litter. Microparticles (30 μm diameter) were injected to determine if physical occlusion and focal inflammation within distal pulmonary arteries might initiate plexiform lesion development. Three months postinjection no plexiform lesions were observed in the vicinity of persisting microparticles. Broiler chickens selected for innate susceptibility to IPAH represent a new animal model for investigating the mechanisms responsible for spontaneous plexogenic arteriopathy.

Idiopathic pulmonary arterial hypertension: an avian model for plexogenic arteriopathy and serotonergic vasoconstriction

Idiopathic pulmonary arterial hypertension (IPAH) is a disease of unknown cause that is characterized by elevated pulmonary arterial pressure and pulmonary vascular resistance attributable to vasoconstriction and vascular remodeling of small pulmonary arteries. Vascular remodeling includes hypertrophy and hyperplasia of smooth muscle (medial hypertrophy) accompanied in up to 80% of the cases by the formation of occlusive plexiform lesions (plexogenic arteriopathy). Patients tend to be unresponsive to vasodilator therapy and have a poor prognosis for survival when plexogenic arteriopathy progressively obstructs their pulmonary arteries. Research is needed to understand and treat plexogenic arteriopathy, but advances have been hindered by the absence of spontaneously developing lesions in existing laboratory animal models. Young domestic fowl bred for meat production (broiler chickens, broilers) spontaneously develop IPAH accompanied by semi-occlusive endothelial proliferation that progresses into fully developed plexiform lesions. Plexiform lesions develop in both female and male broilers, and lesion incidences (lung sections with lesions/lung sections examined) averaged approximately 40% in 8 to 52 week old birds. Plexiform lesions formed distal to branch points in muscular interparabronchial pulmonary arteries, and were associated with perivascular mononuclear cell infiltrates. Serotonin (5-hydroxytryptamine, 5-HT) is a potent vasoconstrictor and mitogen known to stimulate vascular endothelial and smooth muscle cell proliferation. Serotonin has been directly linked to the pathogenesis of IPAH in humans, including IPAH linked to serotonergic anorexigens that trigger the formation of plexiform lesions indistinguishable from those observed in primary IPAH triggered by other causes. Serotonin also plays a major role in the susceptibility of broilers to IPAH. This avian model of spontaneous IPAH constitutes a new animal model for biomedical research focused on the pathogenesis of IPAH and plexogenic arteriopathy.

Pulmonary arterial hypertension associated with chronic active Epstein-Barr virus infection

A 45-year-old man with chronic active Epstein-Barr virus (EBV) infection (CAEBV) with natural killer cell type developed pulmonary arterial hypertension (PAH). After chemotherapy, he showed marked depression of the EBV DNA genome in the peripheral blood, but PAH sustained. He died of heart failure due to PAH, and the histo-pathological examination revealed pulmonary vascular abnormalities without lung disease on autopsy. Although the EBV DNA genome and the infiltrating lymphocytes were not detected in the lung, his clinical course suggested that his PAH might be caused by CAEBV. This is the first reported case of PAH associated CAEBV in an adult.

Endothelial progenitor cells in pulmonary hypertension - dawn of cell-based therapy?

There is mounting interest in the concept of endothelial progenitor cell (EPC) therapy for the treatment of pulmonary arterial hypertension (PAH). Recent successful pilot studies in idiopathic PAH have raised questions about the contribution of progenitor cells circulating in the peripheral blood to pulmonary vascular homeostasis and to the process of vascular remodelling. This review will summarise the work performed to date in animal and human therapeutic trials and clarify what is known about the potential contribution of EPCs to the pathophysiology of PAH.

Genomics of pulmonary arterial hypertension: implications for therapy

Pulmonary arterial hypertension (PAH) remains a vexing clinical disease with no cure. Despite advances and the discovery of a gene (BMPR2) associated with many of the hereditary forms of the disease, and some cases not previously known to be inherited, the reasons for mutations in this gene as a cause remain somewhat elusive. Clearly, a complex interplay exists between genetic alterations, environmental exposures (including infections), and disease development. This article addresses the advances in the genetics of PAH, including the identification of genetic etiologies and modulators, and the role of genetics in predicting disease progression and targeting therapeutics.

Involvement of the bone morphogenetic protein system in endothelin- and aldosterone-induced cell proliferation of pulmonary arterial smooth muscle cells isolated from human patients with pulmonary arterial hypertension

Recent genetic studies have uncovered a link between familial and idiopathic pulmonary arterial hypertension (PAH) and germline mutations in the bone morphogenetic protein type-II receptor (BMPRII). The pathology of PAH is characterized by remodeling of the pulmonary arteries due to pulmonary artery smooth muscle cell (PASMC) hyperproliferation. Although increased endothelial injury and impaired suppression of PASMC proliferation are both critical for the cellular pathogenesis of PAH, a detailed molecular mechanism underlying PAH has yet to be elucidated. In the present study, we investigated the roles of the BMP system and other vasoactive factors associated with PAH (including endothelin (ET), angiotensin II (Ang II) and aldosterone) in the mitotic actions of PASMCs isolated from idiopathic and secondary PAH lungs. ET1 and aldosterone stimulated PASMC proliferation of idiopathic PAH more effectively than secondary PAH, whereas Ang II and ET3 failed to activate mitosis in either of the PASMC cell type. The effects of ET1 and aldosterone were blocked by bosentan, an ET type-A/B receptor (ETA/BR) antagonist, and eplerenone, a selective mineralocorticoid receptor (MR) blocker, respectively. Among the BMP ligands examined, BMP-2 and BMP-7, but not BMP-4 or BMP-6, significantly increased cell mitosis in both PASMC cell types. Notably, ET1- and aldosterone-induced mitosis and mitogen-activated protein kinase phosphorylation were significantly increased in the presence of BMP-2 and BMP-7 in PASMCs isolated from idiopathic PAH, although additive effects were not observed in PASMCs isolated from secondary PAH. Inhibition of extracellular signal-regulated kinase 1 (ERK1)/ERK2 signaling suppressed basal-, ET1- and aldosterone-induced PASMC mitosis more potently than that of stress-activated protein kinase/c-Jun NH2-terminal kinase inhibition. Given the fact that BMP-2 and BMP-7 upregulated ETA/BR and MR expression and that BMP-2 decreased 11betaHSD2 (11beta-hydroxysteroid dehydrogenase type 2) levels in PASMCs isolated from idiopathic PAH, BMPR-Smad signaling may have a key role in amplifying the ETA/BR and/or MR-ERK signaling in PASMCs of the PAH lung. Collectively, the functional link between BMP and ET and/or the MR system may be involved in the progress of PASMC mitosis, ultimately leading to the development of clinical PAH.

Increased concentrations of serotonin and 5-hydroxyindoleacetic acid in blood plasma from patients with pulmonary hypertension due to mitral valve disease

Serotonin content in the plasma and platelets and 5-hydroxyindoleacetic acid concentration in the plasma were shown to increase in patients with pulmonary arterial hypertension due to mitral valve disease. A positive correlation was found between the severity of pulmonary arterial hypertension and concentrations of serotonin (r=0.48) and 5-hydroxyindoleacetic acid in the plasma (r=0.9).

Animal models of pulmonary arterial hypertension: the hope for etiological discovery and pharmacological cure

At present, six groups of chronic pulmonary hypertension (PH) are described. Among these, group 1 (and 1′) comprises a group of diverse diseases termed pulmonary arterial hypertension (PAH) that have several pathophysiological, histological, and prognostic features in common. PAH is a particularly severe and progressive form of PH that frequently leads to right heart failure and premature death. The diagnosis of PAH must include a series of defined clinical parameters, which extend beyond mere elevations in pulmonary arterial pressures and include precapillary PH, pulmonary hypertensive arteriopathy (usually with plexiform lesions), slow clinical onset (months or years), and a chronic time course (years) characterized by progressive deterioration. What appears to distinguish PAH from other forms of PH is the severity of the arteriopathy observed, the defining characteristic of which is “plexogenic arteriopathy.” The pathogenesis of this arteriopathy remains unclear despite intense investigation in a variety of animal model systems. The most commonly used animal models (“classic” models) are rodents exposed to either hypoxia or monocrotaline. Newer models, which involve modification of classic approaches, have been developed that exhibit more severe PH and vascular lesions, which include neointimal proliferation and occlusion of small vessels. In addition, genetically manipulated mice have been generated that have provided insight into the role of specific molecules in the pulmonary hypertensive process. Unfortunately, at present, there is no perfect preclinical model that completely recapitulates human PAH. All models, however, have provided and will continue to provide invaluable insight into the numerous pathways that contribute to the development and maintenance of PH. Use of both classic and newly developed animal models will allow continued rigorous testing of new hypotheses regarding pathogenesis and treatment. This review highlights progress that has been made in animal modeling of this important human condition.

Evidence of dysfunction of endothelial progenitors in pulmonary arterial hypertension

RATIONALE

Severe pulmonary arterial hypertension (PAH) is characterized by the formation of plexiform lesions and concentric intimal fibrosis in small pulmonary arteries. The origin of cells contributing to these vascular lesions is uncertain. Endogenous endothelial progenitor cells are potential contributors to this process.

OBJECTIVES

To determine whether progenitors are involved in the pathobiology of PAH.

METHODS

We performed immunohistochemistry to determine the expression of progenitor cell markers (CD133 and c-Kit) and the major homing signal pathway stromal cell-derived factor-1 and its chemokine receptor (CXCR4) in lung tissue from patients with idiopathic PAH, familial PAH, and PAH associated with congenital heart disease. Two separate flow cytometric methods were employed to determine peripheral blood circulating numbers of angiogenic progenitors. Late-outgrowth progenitor cells were expanded ex vivo from the peripheral blood of patients with mutations in the gene encoding bone morphogenetic protein receptor type II (BMPRII), and functional assays of migration, proliferation, and angiogenesis were undertaken. measurements and main results: There was a striking up-regulation of progenitor cell markers in remodeled arteries from all patients with PAH, specifically in plexiform lesions. These lesions also displayed increased stromal cell-derived factor-1 expression. Circulating angiogenic progenitor numbers in patients with PAH were increased compared with control subjects and functional studies of late-outgrowth progenitor cells from patients with PAH with BMPRII mutations revealed a hyperproliferative phenotype with impaired ability to form vascular networks.

CONCLUSIONS

These findings provide evidence of the involvement of progenitor cells in the vascular remodeling associated with PAH. Dysfunction of circulating progenitors in PAH may contribute to this process.

Update in nonneoplastic lung diseases

CONTEXT

Nonneoplastic lung diseases include a wide range of pathologic disorders from asthma to interstitial lung disease to pulmonary hypertension. Recent advances in our understanding of the pathophysiology of many of these disorders may ultimately impact diagnosis, therapy, and prognosis. It is important for the practicing pathologist to be aware of this new information and to understand how it impacts the diagnosis, treatment, and outcome of these diseases.

OBJECTIVE

To update current progress toward elucidating the pathophysiology of pulmonary alveolar proteinosis, idiopathic pulmonary hemosiderosis, and pulmonary arterial hypertension, as well as to present classification systems for pulmonary hypertension, asthma, and interstitial lung disease and describe how these advances relate to the current practice of pulmonary pathology.

DATA SOURCES

Published literature from PubMed (National Library of Medicine) and primary material from the authors' institution.

CONCLUSIONS

Improved understanding of the pathophysiology of pulmonary alveolar proteinosis, pulmonary hypertension, and idiopathic hemosiderosis may impact the role of the surgical pathologist. New markers of disease may need to be assessed by immunohistochemistry or molecular techniques. The classification systems for interstitial lung disease, asthma, and pulmonary hypertension are evolving, and surgical pathologists should consider the clinicopathologic context of their diagnoses of these entities.

Interleukin-6 overexpression induces pulmonary hypertension

Inflammatory cytokine interleukin (IL)-6 is elevated in the serum and lungs of patients with pulmonary artery hypertension (PAH). Several animal models of PAH cite the potential role of inflammatory mediators. We investigated role of IL-6 in the pathogenesis of pulmonary vascular disease. Indices of pulmonary vascular remodeling were measured in lung-specific IL-6-overexpressing transgenic mice (Tg(+)) and compared to wild-type (Tg(-)) controls in both normoxic and chronic hypoxic conditions. The Tg(+) mice exhibited elevated right ventricular systolic pressures and right ventricular hypertrophy with corresponding pulmonary vasculopathic changes, all of which were exacerbated by chronic hypoxia. IL-6 overexpression increased muscularization of the proximal arterial tree, and hypoxia enhanced this effect. It also reproduced the muscularization and proliferative arteriopathy seen in the distal arteriolar vessels of PAH patients. The latter was characterized by the formation of occlusive neointimal angioproliferative lesions that worsened with hypoxia and were composed of endothelial cells and T-lymphocytes. IL-6-induced arteriopathic changes were accompanied by activation of proangiogenic factor, vascular endothelial growth factor, the proproliferative kinase extracellular signal-regulated kinase, proproliferative transcription factors c-MYC and MAX, and the antiapoptotic proteins survivin and Bcl-2 and downregulation of the growth inhibitor transforming growth factor-beta and proapoptotic kinases JNK and p38. These findings suggest that IL-6 promotes the development and progression of pulmonary vascular remodeling and PAH through proproliferative antiapoptotic mechanisms.

Pulmonary arterial hypertension from a pediatric perspective

This review of pediatric pulmonary arterial hypertension provides a framework within which to view pulmonary hypertension in children. Classification schemes, including the latest recommendations from the World Health Organization, are discussed, and the histopathology of severe pulmonary hypertension is reviewed. New information is provided regarding idiopathic and familial forms of the disease. Specific childhood etiologies, including persistent pulmonary hypertension of the newborn and congenital heart disease, are reviewed. Additionally, we examine the role of collagen vascular diseases, portal hypertension, and viruses in the pathogenesis of severe pulmonary arterial hypertension.

Rosuvastatin provides pleiotropic protection against pulmonary hypertension, right ventricular hypertrophy, and coronary endothelial dysfunction in rats

We recently reported that increased vascular endothelial nitric oxide production could protect against the development of monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH) and right ventricular hypertrophy (RVH) in rats (32). The present study investigated whether the pleiotropic action of 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors in upregulating endothelial function could also protect against the MCT-induced end-organ damages. Rosuvastatin (2 mg kg(-1) day(-1) via oral gavage) or placebo was initiated 1 wk before or 1 wk after MCT (60 mg/kg ip) administration. One month after MCT, significant PAH developed in the placebo rats, which were accompanied by histological evidence of pulmonary vascular thickening and right ventricular hypertrophy. The coronary endothelial vasodilatory function, assessed with endothelial/nitric oxide-dependent responses to acetylcholine and N(G)-nitro-L-arginine methyl ester (L-NAME), was depressed, while the constrictory responses to known coronary constrictors was enhanced. In rats that received rosuvastatin treatment 1 wk before MCT administration, a significantly reduced PAH and RVH was observed, as well as reduced pulmonary vascular and right ventricular remodelings. Rosuvastatin 1-wk posttreatment had no effect on PAH, but inhibited RVH. Right coronary endothelial dysfunction, which was shown in placebo rats, was effectively prevented by both pre- and postrosuvastatin treatment, while this effect was more dramatic in the pretreated group. Left coronary endothelial function, which was not affected by MCT, also showed an upregulation by rosuvastatin. Taken together, our results demonstrated the pleiotropic protection of rosuvastatin against the development of PAH and RVH and confirmed our previous finding that the targeted preservation of coronary endothelial function and vasoactivity may provide a novel approach to protect against cardiac remodeling.