Vascular remodeling in pulmonary hypertension

Pulmonary hypertension is a complex, progressive condition arising from a variety of genetic and pathogenic causes. Patients present with a spectrum of histologic and pathophysiological features, likely reflecting the diversity in underlying pathogenesis. It is widely recognized that structural alterations in the vascular wall contribute to all forms of pulmonary hypertension. Features characteristic of the remodeled vasculature in patients with pulmonary hypertension include increased stiffening of the elastic proximal pulmonary arteries, thickening of the intimal and/or medial layer of muscular arteries, development of vaso-occlusive lesions, and the appearance of cells expressing smooth muscle-specific markers in normally non-muscular small diameter vessels, resulting from proliferation and migration of pulmonary arterial smooth muscle cells and cellular transdifferentiation. The development of several animal models of pulmonary hypertension has provided the means to explore the mechanistic underpinnings of pulmonary vascular remodeling, although none of the experimental models currently used entirely replicates the pulmonary arterial hypertension observed in patients. Herein, we provide an overview of the histological abnormalities observed in humans with pulmonary hypertension and in preclinical models and discuss insights gained regarding several key signaling pathways contributing to the remodeling process. In particular, we will focus on the roles of ion homeostasis, endothelin-1, serotonin, bone morphogenetic proteins, Rho kinase, and hypoxia-inducible factor 1 in pulmonary arterial smooth muscle and endothelial cells, highlighting areas of cross-talk between these pathways and potentials for therapeutic targeting.     

先天性心脏病合并重度肺动脉高压的外科治疗体会

目的总结先天性心脏病合并重度肺动脉高压的外科治疗及有关围手术期的处理经验。方法1998年12月~2006年12月手术治疗先心病合并重度肺动脉高压共121例,男56例,女65例,年龄2~54岁,平均(18.0±9.5)岁。术前肺动脉和体动脉收缩压比Pp/Ps均>0.75,平均(0.95±0.16),动脉血氧饱和度SaO275%~96%。结果手术死亡10例(8.26%)。主要并发症:低心排血量2例,肺高压危象8例。死亡原因:低心排血量,肺高压危象。术后SaO290%~97%,平均(94±2.1)%。患者心功能均较术前改善。结论低心排血量和肺高压危像是合并重度肺高压的先心病患者术后的主要并发症和死亡原因,围术期处理是提高生存率的关键。     

Adiponectin decreases pulmonary arterial remodeling in murine models of pulmonary hypertension

Remodeling of the pulmonary arteries is a common feature among the heterogeneous disorders that cause pulmonary hypertension. In these disorders, the remodeled pulmonary arteries often demonstrate inflammation and an accumulation of pulmonary artery smooth muscle cells (PASMCs) within the vessels. Adipose tissue secretes multiple bioactive mediators (adipokines) that can influence both inflammation and remodeling, suggesting that adipokines may contribute to the development of pulmonary hypertension. We recently reported on a model of pulmonary hypertension induced by vascular inflammation, in which a deficiency of the adipokine adiponectin (APN) was associated with the extensive proliferation of PASMCs and increased pulmonary artery pressures. Based on these data, we hypothesize that APN can suppress pulmonary hypertension by directly inhibiting the proliferation of PASMCs. Here, we tested the effects of APN overexpression on pulmonary arterial remodeling by using APN-overexpressing mice in a model of pulmonary hypertension induced by inflammation. Consistent with our hypothesis, mice that overexpressed APN manfiested reduced pulmonary hypertension and remodeling compared with wild-type mice, despite developing similar levels of pulmonary vascular inflammation in the model. The overexpression of APN was also protective in a hypoxic model of pulmonary hypertension. Furthermore, APN suppressed the proliferation of PASMCs, and reduced the activity of the serum response factor-serum response element pathway, which is a critical signaling pathway for smooth muscle cell proliferation. Overall, these data suggest that APN can regulate pulmonary hypertension and pulmonary arterial remodeling through its direct effects on PASMCs. Hence, the activation of APN-like activity in the pulmonary vasculature may be beneficial in pulmonary hypertension.     

P-selectin gene polymorphism associates with pulmonary hypertension in congenital heart disease

Objective: To investigate the relationship between P-selectin gene polymorphism and congenital heart disease (CHD) with pulmonary hypertension (PAH). Methods: 58 CHD patients with PAH (PAH-CHD), 43 CHD patients without PAH and 205 healthy subjects were included in this study. The concentration of plasma P-selectin was determined by ELISA kits; the direct sequencing of PCR products was used to analyze the P-selectin genotypes. Results: The concentration of plasma P-selectin was markedly higher in PAH-CHD patients than that in CHD subjects and controls, while no difference was observed between CHD group and control. A significant difference of P-selectin genotype -825T/C polymorphism was observed between patients with PAH-CHD and healthy subjects (P<0.05). Logistic analysis showed that the subjects with haplotypes A-G and G-G had lower risk of PAH-CHD compared with the ones with haplotype A-A (OR=0.47, 95% CI=0.24-0.92). In the subjects of PAH-CHD and control, plasma P-selectin concentration was higher in subjects with -825TT genotype than the ones with haplotypes T-C and C-C (P<0.05). Conclusion: P-selectin probably involves in the development of PAH-CHD. The polymorphism of -825T/C is associated with the risk of PAH-CHD, and may be one of its risk factors.     

Conventional radiology and right heart catheterization in estimating primary pulmonary hypertension and pulmonary hypertension secondary to left-sided valvular disease

Aim: to estimate the comparative value of conventional radiology and cardiac catheterization in establishing the diagnosis and severity of primary and secondary pulmonary hypertension. We also tried to achieve some correlations between the radiological and invasive parameters. Methods: we performed a retrospective study over an 11-years time period, analyzing data from a group of 14 patients diagnosed with primary pulmonary hypertension compared to a matched group of 20 patients suffering from pulmonary hypertension secondary to mitral and aortic valvular disease. All the patients had undergone conventional radiology (chest X-ray) and catheterization of the right heart cavities and pulmonary artery. Results: we detected significantly elevated pulmonary artery pressures and resistances in the primary pulmonary hypertension group compared to secondary hypertension patients. Cardiac output values were much lower in the primary pulmonary hypertension individuals compared with secondary pulmonary hypertension in left-sided valvular disease. The pulmonary artery arch diameter, the diameter of the right descending pulmonary artery and the value of the arterio-bronchial ratio were similar in the two groups. Conclusion: in both groups, we found a statistically significant positive correlation between the values of the pulmonary artery vascular resistance and the diameter of the right descending pulmonary artery, which are very specific parameters in the diagnosis of pulmonary hypertension. In the primary pulmonary hypertension group we identified a significant inverse correlation between the diameter of the right descending pulmonary artery and the values of cardiac output. This finding was not confirmed in the secondary group.     

伊洛前列素治疗儿童先天性心脏病术后肺动脉高压对血液流变学的影响

目的:观察吸入伊洛前列素治疗先天性心脏病术后肺动脉高压患儿的血液流变学指标变化.方法:随机选择10例术后未吸入伊洛前列素患儿,10例术后24 h吸入伊洛前列素患儿,年龄0～14岁.运用血液流变学仪检测吸入伊洛前列素前后3项血液流变学指标.结果:与未吸入伊洛前列素组相比,吸入伊洛前列素后24 h患儿红细胞聚集性和血液屈服...     

伴肺动脉高压的先天性心脏病患儿肺组织病理学观察

目的　探讨左向右分流型先天性心脏病患儿肺组织的病理形态学改变、超微结构改变与肺动脉高压 (pulmonaryhy pertension ,PH)形成的关系。方法　应用光镜、电镜、组织化学染色 ,对 4 1例先心病患儿肺组织及肺各级小动脉进行研究、分析。结果　伴有PH的肺组织各级小动脉 (包括部分肌型及肌型动脉 )数量增加、管壁增厚、管腔狭窄 ,尤以中重度PH患者显著 ,主要表现血管中膜平滑肌 (SMC)和内皮细胞 (EC)增生 ,内弹力膜增厚 ,外膜胶原纤维增多。先天性心脏病患儿肺组织内无肌型小动脉肌化、部分肌型及肌型小动脉数量增加 ,随着PH的增高 ,差异有显著性 (P <0 0 1)。超微结构改变包括 :①肺泡隔纤维化逐渐明显 ,胶原纤维增生 ;②小动脉中膜SMC层数明显增加 ,SMC细胞面积增大 ,核染色质增粗 ,细胞间间隙明显增宽 ,血管外膜胶原纤维高度密集 ;③小动脉血管内皮细胞增生呈高柱状 ,细胞线粒体肿胀、空泡化 ,吞饮小泡多见 ;④毛细血管充血、瘀血 ,基膜明显增厚。结论　先心病引起缺氧导致肺血管重建 ,使肺血管阻力增加 ,是PH形成的关键因素 ,肺毛细血管的超微结构病变所致微循环障碍更加促进了PH的发生、发展。     

Fibrous remodeling of the pulmonary venous system in pulmonary arterial hypertension associated with connective tissue diseases

Pulmonary arterial hypertension is a severe complication of connective tissue diseases. It is currently well established that pulmonary arterial hypertension associated with connective tissue diseases such as systemic sclerosis is frequently less responsive or even refractory to pulmonary vasodilator therapies. In that setting, pulmonary venoocclusive disease is believed to contribute to treatment failures. We therefore hypothesized that pulmonary arterial hypertension associated with connective tissue diseases may be associated with obstructive lesions of pulmonary veins. Lung samples from 8 patients with pulmonary arterial hypertension associated with connective tissue disease (4 limited systemic sclerosis, 2 systemic lupus erythematosus, 1 mixed connective tissue diseases, and 1 rheumatoid arthritis) were studied by light microscopy and analyzed by immunohistochemistry (5 postmortem samples, 3 explants after lung transplantation). Findings were compared with 29 pulmonary arterial hypertension cases from patients displaying neither connective tissue diseases nor associated conditions. We found that (a) 6 (75%) of 8 patients with pulmonary arterial hypertension associated with connective tissue diseases showed significant obstructive pulmonary vascular lesions predominating in veins/preseptal venules, as compared with 5 (17.2%) of 29 non-connective tissue diseases control pulmonary arterial hypertension; (b) lesions of small muscular arteries were consistently present in pulmonary arterial hypertension associated with connective tissue diseases, showing mostly intimal fibrosis and thrombotic lesions; and (c) 6 of 8 lung samples from patients with pulmonary arterial hypertension associated with connective tissue diseases revealed perivascular inflammatory infiltration. In conclusion, our study highlights the fact that pulmonary arterial hypertension complicating the course of connective tissue diseases may be characterized by a more frequent involvement of pulmonary veins and may thus explain why these patients are less prone to respond to specific pulmonary arterial hypertension treatment as compared with idiopathic pulmonary arterial hypertension.     

Animal models of pulmonary hypertension due to left heart disease

Pulmonary hypertension due to left heart disease (PH‐LHD) is regarded as the most prevalent form of pulmonary hypertension (PH). Indeed, PH is an independent risk factor and predicts adverse prognosis for patients with left heart disease (LHD). Clinically, there are no drugs or treatments that directly address PH‐LHD, and treatment of LHD alone will not also ameliorate PH. To target the underlying physiopathological alterations of PH‐LHD and to develop novel therapeutic approaches for this population, animal models that simulate the pathophysiology of PH‐LHD are required. There are several available models for PH‐LHD that have been successfully employed in rodents or large animals by artificially provoking an elevated pressure load on the left heart, which by transduction elicits an escalated pressure in pulmonary artery. In addition, metabolic derangement combined with aortic banding or vascular endothelial growth factor receptor antagonist is also currently applied to reproduce the phenotype of PH‐LHD. As of today, none of the animal models exactly recapitulates the condition of patients with PH‐LHD. Nevertheless, the selection of an appropriate animal model is essential in basic and translational studies of PH‐LHD. Therefore, this review will summarize the characteristics of each PH‐LHD animal model and discuss the advantages and limitations of the different models.     

Vascular remodeling in primary pulmonary hypertension. Potential role for transforming growth factor-beta.

Active exogenous transforming growth factor-beta s (TGF-beta s) are potent modulators of extracellular matrix synthesis in cell culture and stimulate matrix synthesis in wounds and other remodeling tissues. The role of endogenous TGF-beta s in remodeling tissues is less well defined. Vascular remodeling in the pulmonary arteries of patients with primary pulmonary hypertension is characterized, in part, by abnormal deposition of immunohistochemically detectable procollagen, thereby identifying actively remodeling vessels. We used this marker of active matrix synthesis to begin defining the in vivo role of TGF-beta in the complex milieu of actively remodeling tissues. Immunohistochemistry using isoform-specific anti-TGF-beta antibodies was performed to determine whether TGF-beta was present in actively remodeling hypertensive pulmonary arteries 20 to 500 microns in diameter. Intense, cell-associated TGF-beta 3 immunoreactivity was observed in the media and neointima of these hypertensive muscular arteries. Immunostaining was present, but less intense, in normal arteries of comparable size. TGF-beta 2 immunoreactivity was observed in normal vessels and was increased slightly in hypertensive vessels, in a pattern resembling TGF-beta 3 immunoreactivity. No staining was associated with the adventitia. TGF-beta 1 immunostaining was either faint or absent in both normal and hypertensive vessels. Comparison of procollagen and TGF-beta localization demonstrated that TGF-beta 2 and TGF-beta 3 colocalized at all sites of procollagen synthesis. However, TGF-beta was observed in vessels, or vascular compartments, where there was no procollagen synthesis. Procollagen immunoreactivity was not present in normal vessels that showed immunoreactivity for TGF-beta 2 and TGF-beta 3. These observations suggest: a) the stimulation of procollagen synthesis by TGF-beta in vivo is more complex than suggested by in vitro studies and b) a potential role for TGF-beta 2 or TGF-beta 3, but not TGF-beta 1, in hypertensive pulmonary vascular remodeling.     

Leukotrienes in pulmonary arterial hypertension

Leukotrienes (LTs) are lipid mediators derived from the 5-lipoxygenase (5-LO) pathway of arachidonic acid metabolism and are markers and mediators of pulmonary inflammation. Research over the past two decades has established that LTs modulate inflammation in pulmonary arterial hypertension (PAH). The purpose of this review was to summarize the current knowledge of LTs in the pathophysiology of PAH and to highlight a recent study that advances our understanding of how leukotriene B₄ (LTB₄) specifically contributes to pulmonary vascular remodeling. The results of these studies suggest that pharmacological inhibition of LT pathways, especially LTB₄, has high potential for the treatment of PAH.     

Sildenafil in pediatric pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening disease of varied etiologies. Although PAH has no curative treatment, a greater understanding of pathophysiology, technological advances resulting in early diagnosis, and the availability of several newer drugs have improved the outlook for patients with PAH. Sildenafil is one of the therapeutic agents used extensively in the treatment of PAH in children, as an off-label drug. In 2012, the United States Food and Drug Administration (USFDA) issued a warning regarding the of use high-dose sildenafil in children with PAH. This has led to a peculiar situation where there is a paucity of approved therapies for the management of PAH in children and the use of the most extensively used drug being discouraged by the regulator. This article provides a review of the use of sildenafil in the treatment of PAH in children.KEY WORDS: Child, phosphodiesterase (PDE)-5 inhibitor, Pulmonary hypertension therapy     

先天性心脏病伴肺动脉高压内皮素-1和内皮型一氧化氮合酶的表达

目的：研究内皮素-1（ET-1）及内皮型一氧化氮合酶（eNOS）对先天性心脏病伴肺动脉高压（PH）的调控作用。 方法： 将40例先天性心脏病患儿按其肺动脉收缩压分为中重度PH组12例、轻度PH组14例、无PH组14例；另选取10例非心脏疾患手术病人10例作为对照组。采用放射免疫、硝酸还原酶、透射电镜、免疫组化等方法，观察各组患儿肺细小动脉超微结构、血ET-1、一氧化氮（NO）浓度及肺细小动脉ET-1、eNOS蛋白表达的变化。 结果： ①血浆ET-1水平，中重度PH组、轻度PH组明显高于无PH组（P<0.01）；血清NO浓度中重度PH组、轻度PH组明显低于无PH组（P<0.01）。 ②电镜下,中重度PH组肺细小动脉中膜平滑肌增生，外膜胶原纤维密集；轻度PH组肺细小动脉中膜平滑肌细胞和外膜胶原纤维增生轻于中重度PH组；无PH组肺细小动脉结构改变不明显。③免疫组化显示中重度PH组、轻度PH组肺细小动脉ET-1平均吸光度值显著高于无PH组(P<0.01)；而中重度PH组、轻度PH组肺细小动脉eNOS平均吸光度值显著低于无PH组(P<0.01)。 结论： ET-1、eNOS可能参与了先天性心脏病PH的形成与肺血管结构重建。