Heterogeneous Characteristics of Lymphatic Microvasculatures Associated with Pulmonary Sarcoid Granulomas

Genetic and geographic influence on phenotypic variation in European sarcoidosis patients

Introduction

Sarcoidosis is a highly variable disease in terms of organ involvement, type of onset and course. Associations of genetic polymorphisms with sarcoidosis phenotypes have been observed and suggest genetic signatures.

Methods

After obtaining a positive vote of the competent ethics committee we genotyped 1909 patients of the deeply phenotyped Genetic-Phenotype Relationship in Sarcoidosis (GenPhenReSa) cohort of 31 European centers in 12 countries with 116 potentially disease-relevant single-nucleotide polymorphisms (SNPs). Using a meta-analysis, we investigated the association of relevant phenotypes (acute vs. sub-acute onset, phenotypes of organ involvement, specific organ involvements, and specific symptoms) with genetic markers. Subgroups were built on the basis of geographical, clinical and hospital provision considerations.

Results

In the meta-analysis of the full cohort, there was no significant genetic association with any considered phenotype after correcting for multiple testing. In the largest sub-cohort (Serbia), we confirmed the known association of acute onset with TNF and reported a new association of acute onset an HLA polymorphism. Multi-locus models with sets of three SNPs in different genes showed strong associations with the acute onset phenotype in Serbia and Lublin (Poland) demonstrating potential region-specific genetic links with clinical features, including recently described phenotypes of organ involvement.

Discussion

The observed associations between genetic variants and sarcoidosis phenotypes in subgroups suggest that gene-environment-interactions may influence the clinical phenotype. In addition, we show that two different sets of genetic variants are permissive for the same phenotype of acute disease only in two geographic subcohorts pointing to interactions of genetic signatures with different local environmental factors. Our results represent an important step towards understanding the genetic architecture of sarcoidosis.

The lymphatic vasculature in lung function and respiratory disease

The lymphatic vasculature maintains tissue homeostasis via fluid drainage in the form of lymph and immune surveillance due to migration of leukocytes through the lymphatics to the draining lymph nodes. Lymphatic endothelial cells (LECs) form the lymphatic vessels and lymph node sinuses and are key players in shaping immune responses and tolerance. In the healthy lung, the vast majority of lymphatic vessels are found along the bronchovascular structures, in the interlobular septa, and in the subpleural space. Previous studies in both mice and humans have shown that the lymphatics are necessary for lung function from the neonatal period through adulthood. Furthermore, changes in the lymphatic vasculature are observed in nearly all respiratory diseases in which they have been analyzed. Recent work has pointed to a causative role for lymphatic dysfunction in the initiation and progression of lung disease, indicating that these vessels may be active players in pathologic processes in the lung. However, the mechanisms by which defects in lung lymphatic function are pathogenic are understudied, leaving many unanswered questions. A more comprehensive understanding of the mechanistic role of morphological, functional, and molecular changes in the lung lymphatic endothelium in respiratory diseases is a promising area of research that is likely to lead to novel therapeutic targets. In this review, we will discuss our current knowledge of the structure and function of the lung lymphatics and the role of these vessels in lung homeostasis and respiratory disease.

Association of proangiogenic and profibrotic serum markers with lung function and quality of life in sarcoidosis

Background

Sarcoidosis is a systemic inflammatory granulomatous disease, frequently affecting the lung. If left untreated, it may end in lung fibrosis. Proangiogenic and profibrotic vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β1, fibroblast growth factor (FGF)-2 and platelet-derived growth factor (PDGF)-AB are a known therapeutical target in pulmonary fibrosing diseases, e.g. IPF, but there is no targeted therapy option for pulmonary fibrosis in sarcoidosis.

Objectives

The aim of our study was to determine the association of these markers’ serum levels on lung function and the patients’ quality of life in a long-term follow-up of sarcoidosis patients, to provide further information for finding targeted therapy options for pulmonary sarcoidosis.

Methods

54 patients with sarcoidosis underwent blood sampling, pulmonary function testing and answered the King’s Brief Interstitial Lung Disease (K-BILD) questionnaire at baseline and at three-years follow-up. Serum levels of profibrotic and angiogenic markers were assessed at baseline by enzyme-linked immunosorbent assay.

Results

Between 2015 and 2018, 54 patients with biopsy proven sarcoidosis were enrolled. Throughout the observation period, there was a significant decrease in the diffusion capacity for carbon monoxide (DLCO) [%] (-6.5504 ± 13,39, p = 0.001) and forced expiratory volume in one second predicted (FEV1) [%] (-6.07 ± 12.09, p = 0.001). Patients with greater impairment of forced vital capacity (FVC) did have significantly higher serum levels of VEGF (p = 0.03) and PDGF-AB (p<0.001). The K-BILD questionnaire did not change significantly during follow-up. However, patients with worsening K-BILD scores did have significantly higher serum-levels of PDGF-AB (2.67 pg/ml ± 0.93 vs. 1.88 pg/ml ± 0.60, p = 0.004) at baseline, compared to those with unchanged or increasing K-BILD scores.

Conclusions

Among patients with pulmonary sarcoidosis, baseline serum levels of VEGF and PDGF-AB were associated with pulmonary function impairment. Furthermore, PDGF-AB was associated with worsening K-BILD scores. No such association was observed for FGF-2 and TGF-ß1. VEGF and PDGF-AB may be possible prognostic and therapeutic targets in sarcoidosis as a fibrosing ILD beyond IPF.

Identification of Specific Endobronchial Ultrasound Features to Differentiate Sarcoidosis From Other Causes of Lymphadenopathy

OBJECTIVES

We hypothesized that specific endobronchial ultrasound (EBUS) features may differentiate sarcoidosis from other causes of lymphadenopathy.

METHODS

We conducted this retrospective observational study from January 2014 to January 2019 to analyze patients with intrathoracic lymphadenopathy who underwent EBUS-guided transbronchial needle aspiration. Ultrasound features, including nodal size, margin, echogenicity, the presence or absence of calcification, a central hilar structure, the coagulation necrosis sign, nodal conglomeration, and the septal vessel sign in the color Doppler mode were recorded and compared between 3 groups.

RESULTS

Of the 90 included patients, 15 had a diagnosis of tuberculosis; 56 had a diagnosis of sarcoidosis; and 19 had a diagnosis of malignant lymph nodes by EBUS-guided transbronchial needle aspiration. The presence of nodal conglomeration (94.6% versus 60.0% versus 5.3%; P < .001), the septal vessel sign in the color Doppler mode (55.4% versus 13.3% versus 15.8%; P = .002), and a distinct margin (73.2% versus 13.3% versus 47.4%; P < .001) were significantly higher in the sarcoidosis group than in the tuberculosis lymphadenopathy and malignant lymph node groups. The presence of the coagulation necrosis sign (8.9% versus 93.3% versus 31.6%; P < .001) was significantly lower in the sarcoidosis group than in tuberculosis lymphadenopathy and malignant lymph node groups. A multivariate analysis showed that the presence of nodal conglomeration, the absence of coagulation necrosis, and the presence of the septal vessel sign in the color Doppler mode were independent predictive factors for the diagnosis of sarcoidosis.

CONCLUSIONS

The presence of nodal conglomeration, the absence of coagulation necrosis, and the presence of the septal vessel sign in the color Doppler mode in lymph nodes on EBUS are predictive of sarcoidosis.

Granulomatous Inflammation in Tuberculosis and Sarcoidosis: Does the Lymphatic System Contribute to Disease?

A striking and unexplained feature of granulomatous inflammation is its anatomical association with the lymphatic system. Accumulating evidence suggests that lymphatic tracks and granulomas may alter the function of each other. The formation of new lymphatics, or lymphangiogenesis, is an adaptive response to tumor formation, infection, and wound healing. Granulomas also may induce lymphangiogenesis which, through a variety of mechanisms, could contribute to disease outcomes in tuberculosis and sarcoidosis. On the other hand, alterations in lymph node function and lymphatic draining may be primary events which attenuate the risk and severity of granulomatous inflammation. This review begins with an introduction of granulomatous inflammation and the lymphatic system. A role of the lymphatic system in tuberculosis and sarcoidosis is then hypothesized. With a focus on lymphangiogenesis in these diseases, and on the potential for this process to promote dissemination, parallels are established with the well-established role of lymphangiogenesis in tumor biology.

A potential role of toll-like receptors, IFN-γ and the phosphatidylinositol 3-kinase pathway in the pathogenesis of acquired mediastinal lymphatic malformation

Sarcoidosis is a multisystem disorder with non-caseating granulomas in various organs. The etiology of sarcoid granuloma formation is not clear and likely an antigen-induced process. We came across a previously treated sarcoidosis patient who presented with worsening dyspnea on exertion for several months and several days of difficulty swallowing. On Chest CT imaging, large posterior mediastinal mass was found that subsequently diagnosed as macrocystic lymphatic malformation after surgical resection. Pathophysiology of development of acquired lymphatic malformations in a sarcoidosis patient is currently not clear. We hypothesize there might be a complex interplay of Toll-like receptors, IFN-γ and the phosphatidylinositol 3-kinase pathway in the pathogenesis.

Pulmonary lymphatic vessel morphology: a review

Our understanding of lymphatic vessels has been advanced by the recent identification of relatively specific lymphatic endothelium markers, including Prox-1, VEGFR3, podoplanin and LYVE-1. The use of lymphatic markers has led to the observation that, contrary to previous assumptions, human lymphatic vessels extend deep inside the pulmonary lobule, either in association with bronchioles, intralobular arterioles or small pulmonary veins. Pulmonary lymphatic vessels may thus be classified into pleural, interlobular (in interlobular septa) and intralobular. Intralobular lymphatic vessels may be further subdivided in: bronchovascular (associated with a bronchovascular bundle), perivascular (associated with a blood vessel), peribronchiolar (associated with a bronchiole), and interalveolar (in interalveolar septa). Most of the intralobular lymphatic vessels are in close contact with a blood vessel, either alone or within a bronchovascular bundle. A minority is associated with a bronchiole, and small lymphatics are occasionally present even in interalveolar septa, seemingly independent of blood vessels or bronchioles. The lymphatics of the interlobular septa often contain valves, are usually associated with the pulmonary veins, and connect with the pleural lymphatics. The large lymphatics associated with bronchovascular bundles have similar characteristics to pleural and interlobular lymphatics and may be considered conducting vessels. The numerous small perivascular lymphatics and the few peribronchiolar ones that are found inside the lobule are probably the absorbing compartment of the lung responsible for maintaining the alveolar interstitium relatively dry in order to provide a minimal thickness of the air-blood barrier and thus optimize gas diffusion. These lymphatic populations could be differentially involved in the pathogenesis of diseases preferentially involving distinct lung compartments.

Lymphatic Vessels: The Next Frontier in Lung Transplant

Lymphatic vessels are essential for the uptake of fluid, immune cells, macromolecules, and lipids from the interstitial space. During lung transplant surgery, the pulmonary lymphatic vessel continuum is completely disrupted, and, as a result, lymphatic drainage function is severely compromised. After transplantation, the regeneration of an effective lymphatic drainage system plays a crucial role in maintaining interstitial fluid balance in the lung allograft. In the meantime, these newly formed lymphatic vessels are commonly held responsible for the development of immune responses leading to graft rejection, because they are potentially capable of transporting antigen-presenting cells loaded with allogeneic antigens to the draining lymph nodes. However, despite remarkable progress in the understanding of lymphatic biology, there is still a paucity of consistent evidence that demonstrates the exact impacts of lymphatic vessels on lung graft function. In this review, we examine the current literature related to roles of lymphatic vessels in the pathogenesis of lung transplant rejection.

Lymphatic Changes in Respiratory Diseases: More than Just Remodeling of the Lung?

Advances in our ability to identify lymphatic endothelial cells and differentiate them from blood endothelial cells have led to important progress in the study of lymphatic biology. Over the past decade, preclinical and clinical studies have shown that there are changes to the lymphatic vasculature in nearly all lung diseases. Efforts to understand the contribution of lymphatics and their growth factors to disease initiation, progression, and resolution have led to seminal findings establishing critical roles for lymphatics in lung biology spanning from the first breath after birth to asthma, tuberculosis, and lung transplantation. However, in other diseases, it remains unclear if lymphatics are part of the overall lung remodeling process or real contributors to disease pathogenesis. The goal of this Translational Review is to highlight some of the advances in our understanding of the role(s) of lymphatics in lung disease and shed light on the critical needs and unanswered questions that might lead to novel translational applications.

The Lymphatic Phenotype of Lung Allografts in Patients With Bronchiolitis Obliterans Syndrome and Restrictive Allograft Syndrome

BACKGROUND

Chronic lung allograft dysfunction (CLAD), presenting as bronchiolitis obliterans syndrome (BOS) or restrictive allograft syndrome (RAS) is the major limiting factor of long-term survival in lung transplantation. Its pathogenesis is still obscure. In BOS, persistent alloimmune injury and chronic airway inflammation are suggested. One of the main tasks of the lymphatic vessel (LV) system is the promotion of immune cell trafficking. The formation of new LVs has been shown to trigger chronic allograft rejection in kidney transplants. We therefore sought to address the role of lymphangiogenesis in CLAD.

METHODS

Formalin-fixed paraffin-embedded tissue samples of 22 patients receiving a lung retransplantation due to BOS or RAS were collected. Lymphatic vessel density (LVD) was determined by immunohistochemical staining for podoplanin. Lung tissue obtained from 13 non-CLAD patients served as control. The impact of LVD on graft survival was assessed.

RESULTS

Lymphatic vessel density in CLAD patients did not differ from those in control subjects (median number of LVs per bronchiole: 4.75 (BOS), 6.47 (RAS), 4.25 (control), P = 0.97). Moreover, the number of LVs was not associated with regions of cellular infiltrates (median number of LVs per bronchiole: with infiltrates, 5.00 (BOS), 9.00 (RAS), 4.00 (control), P = 0.62; without infiltrates, 4.5 (BOS), 0.00 (RAS), 4.56 (control), P = 0.74). Lymphatic vessel density did not impact the time to development of BOS or RAS in lung transplantation (low vs high LVD: 38.5 vs 86.0 months, P = 0.15 [BOS]; 60.5 vs 69.5 months, P = 0.80 [RAS]).

CONCLUSIONS

Unlike chronic organ failure in kidney transplantation, lymphangiogenesis is not altered in CLAD patients. Our findings highlight unique immunological processes leading to BOS and RAS.

Phenotypically heterogeneous podoplanin-expressing cell populations are associated with the lymphatic vessel growth and fibrogenic responses in the acutely and chronically infarcted myocardium

Cardiac lymphatic vasculature undergoes substantial expansion in response to myocardial infarction (MI). However, there is limited information on the cellular mechanisms mediating post-MI lymphangiogenesis and accompanying fibrosis in the infarcted adult heart. Using a mouse model of permanent coronary artery ligation, we examined spatiotemporal changes in the expression of lymphendothelial and mesenchymal markers in the acutely and chronically infarcted myocardium. We found that at the time of wound granulation, a three-fold increase in the frequency of podoplanin-labeled cells occurred in the infarcted hearts compared to non-operated and sham-operated counterparts. Podoplanin immunoreactivity detected LYVE-1-positive lymphatic vessels, as well as masses of LYVE-1-negative cells dispersed between myocytes, predominantly in the vicinity of the infarcted region. Podoplanin-carrying populations displayed a mesenchymal progenitor marker PDGFRα, and intermittently expressed Prox-1, a master regulator of the lymphatic endothelial fate. At the stages of scar formation and maturation, concomitantly with the enlargement of lymphatic network in the injured myocardium, the podoplanin-rich LYVE-1-negative multicellular assemblies were apparent in the fibrotic area, aligned with extracellular matrix deposits, or located in immediate proximity to activated blood vessels with high VEGFR-2 content. Of note, these podoplanin-containing cells acquired the expression of PDGFRβ or a hematoendothelial epitope CD34. Although Prox-1 labeling was abundant in the area affected by MI, the podoplanin-presenting cells were not consistently Prox-1-positive. The concordance of podoplanin with VEGFR-3 similarly varied. Thus, our data reveal previously unknown phenotypic and structural heterogeneity within the podoplanin-positive cell compartment in the infarcted heart, and suggest an alternate ability of podoplanin-presenting cardiac cells to generate lymphatic endothelium and pro-fibrotic cells, contributing to scar development.

The Serum Expression of Selected miRNAs in Pulmonary Sarcoidosis with/without Löfgren's Syndrome

Purpose. Pulmonary sarcoidosis is associated with dysregulated expression of intracellular miRNAs. There is however only little information on extracellular miRNAs and their association with the disease course in sarcoidosis. We therefore assessed serum miRNAs in sarcoidosis classified according to the presence of Löfgren's syndrome (LS) as a hallmark of good prognosis in contrast to more advanced disease course. Methods. RT-PCR was used to assess 35 miRNAs in 13 healthy controls and 24 sarcoidosis patients (12 with X-ray (CXR) stage ≤ 1 and LS and 12 with insidious onset and CXR stage ≥ 3). Results. Compared to controls, we consistently observed dysregulated expressions of miR-146, miR-16, miR-425-5p, and miR-93-5p in both sarcoidosis groups irrespective of disease course. Specifically, patients without LS had dysregulated expressions of miR-150-5p, miR-1, and miR-212 compared to controls. Patients with LS had dysregulated expressions of miR-21-5p and miR-340-5p compared to controls. Bioinformatics predicted consistently "Pathways in cancer" to be modulated by both altered profiles in patients with/without LS. Three miRNAs (miR-21-5p, miR-340-5p, and miR-212-3p) differed between our patients with LS and those without LS; their cumulative effect may modulate "TGF-β signalling pathway." Conclusions. Further study should focus on possible applications of serum miRNAs for diagnostics follow-up and for prognosis.

Development of Lymphatic Capillary Network Along the Alveolar Walls of Autopsied Human Lungs with Pneumonia

BACKGROUND

Limited information is available regarding the lymphatic vasculature during pneumonia.

OBJECTIVE

To characterize lymphatic vasculatures in autopsied cadavers with pneumonia.

METHODS

Paraffin-embedded lung tissues obtained from 20 autopsied cadavers with complicated pneumonia and 10 control cadavers without pneumonia were used for immunohistochemical analyses using primary antibodies against podoplanin, vascular endothelial growth factor receptor-3 (VEGFR-3), CD34, vascular endothelial growth factor (VEGF)-C, VEGF-D, CD73, and CD163.

RESULTS

There was no difference in the vascular density of podoplanin⁺ usual lymphatics between the individuals with and without pneumonia. In half of the cadavers with pneumonia, however, a network of podoplanin⁺ cells lying together in a side-by-side bead-like arrangement appeared along the alveolar septa; however, this was absent in the control cadavers. The podoplanin⁺ cells in the network were characterized by a weaker expression of podoplanin, relative to usual lymphatics, and the occasional presence of ductal structures. Although podoplanin⁺ cells were not coexpressed with VEGFR-3, a part of the network was connected to CD73⁺ afferent lymphatics. The network showed an intertwined relationship with CD34⁺ capillaries, suggesting that the network represents lymphatic capillaries. The number of CD163⁺ macrophages was significantly increased in individuals with the network than those without the network, while a significant decrease in neutrophils was observed. VEGF-C expressed in CD163⁺ macrophages and type II epithelial cells was observed in the cadavers with the network.

CONCLUSION

The development of lymphatic capillary networks along the alveolar septa rather than the usual lymphangiogenesis was noted in autopsied individuals with pneumonia.

Lymphangiogenesis and Lesion Heterogeneity in Interstitial Lung Diseases

The lymphatic system has several physiological roles, including fluid homeostasis and the activation of adaptive immunity by fluid drainage and cell transport. Lymphangiogenesis occurs in adult tissues during various pathologic conditions. In addition, lymphangiogenesis is closely linked to capillary angiogenesis, and the balanced interrelationship between capillary angiogenesis and lymphangiogenesis is essential for maintaining homeostasis in tissues. Recently, an increasing body of information regarding the biology of lymphatic endothelial cells has allowed us to immunohistochemically characterize lymphangiogenesis in several lung diseases. Particular interest has been given to the interstitial lung diseases. Idiopathic interstitial pneumonias (IIPs) are characterized by heterogeneity in pathologic changes and lesions, as typified by idiopathic pulmonary fibrosis/usual interstitial pneumonia. In IIPs, lymphangiogenesis is likely to have different types of localized functions within each disorder, corresponding to the heterogeneity of lesions in terms of inflammation and fibrosis. These functions include inhibitory absorption of interstitial fluid and small molecules and maturation of fibrosis by excessive interstitial fluid drainage, caused by an unbalanced relationship between capillary angiogenesis and lymphangiogenesis and trafficking of antigen-presenting cells and induction of fibrogenesis via CCL21 and CCR7 signals. Better understanding for regional functions of lymphangiogenesis might provide new treatment strategies tailored to lesion heterogeneity in these complicated diseases.

Immunoexpression of TGF-β/Smad and VEGF-A proteins in serum and BAL fluid of sarcoidosis patients

Background

The chronic course of pulmonary sarcoidosis can lead to lung dysfunction due to fibrosis, in which the signalling pathways TGF-β/Smad and VEGF-A may play a key role.

Methods

We evaluated immunoexpression of TGF-β₁, Smad2, 3, and 7, and VEGF-A in serum and bronchoalveolar lavage (BAL) fluid of patients (n = 57) classified according to the presence of lung parenchymal involvement (radiological stage I vs. II-III), acute vs. insidious onset, lung function test (LFT) results, calcium metabolism parameters, percentage of BAL lymphocytes (BAL-L%), BAL CD4⁺/CD8⁺ ratio, age, and gender. Immunoexpression analysis of proteins was performed by ELISA.

Results

The immunoexpression of all studied proteins were higher in serum than in BAL fluid of patients (p >0.05). The serum levels of TGF-β₁ (p = 0.03), Smad2 (p = 0.01), and VEGF-A (p = 0.0002) were significantly higher in sarcoidosis patients compared to healthy controls. There were no differences within the sarcoidosis group between patients with vs. without parenchymal involvement, acute vs. insidious onset, or patients with normal vs. abnormal spirometry results. In patients with abnormal spirometry results a negative correlation was found between forced vital capacity (FVC) % predicted value and TGF-β₁ immunoexpression in BAL fluid, and positive correlations were observed between the intensity of lung parenchymal changes estimated by high-resolution computed tomography (HRCT scores) and Smad 2 level in serum.

Conclusions

TGF-β/Smad signalling pathway and VEGF-A participate in the pathogenesis of sarcoidosis. BAL TGF-β₁, and Smad 2 in serum seem to be promising biomarkers with negative prognostic value, but further studies are required to confirmed our observations.

Lymphangiogenic factors are associated with the severity of hypersensitivity pneumonitis

Background

Antigen presenting cells play a pivotal role in the adaptive immune response in hypersensitivity pneumonitis (HP). It was hypothesised that lymphangiogenesis is involved in the pathophysiology of HP via cell transport.

Objective

To determine the clinical significance of lymphangiogenic factors in HP.

Methods

Levels of vascular endothelial growth factors (VEGF)-A, VEGF-C, VEGF-D and CCL21 in the serum and bronchoalveolar lavage fluid (BALF) were measured in 29 healthy volunteers, 14 patients with idiopathic pulmonary fibrosis (IPF) and 26 patients with HP by ELISA. Additionally, immunohistochemical analyses were performed using lung specimens of patients with HP (n=8) and IPF (n=10).

Results

BALF VEGF-D levels were significantly elevated in patients with HP compared to the other groups. BALF VEGF–D levels in patients with HP correlated significantly with the BALF total cell and lymphocyte counts (r=0.485, p=0.014 and r=0.717, p<0.0001, respectively). BALF VEGF-C and CCL21 levels were increased in patients with HP compared to healthy volunteers, but not patients with IPF. BALF CCL21 levels were negatively correlated with the forced expiratory volume in 1 s percentage and diffuse capacity of the lung for carbon monoxide (r=−0.662, p=0.007 and r=−0.671, p=0.024, respectively). According to the immunohistochemical analyses, CCL21 was expressed in the lymphatic endothelium in both conditions and CCR7⁺ cells were aggregated around lymphatics in patients with HP, but not in patients with IPF.

Conclusions

Lymphangiogenic factors might be associated with the inflammatory and functional severity of HP. The increased BALF VEGF-D levels were associated with lymphatic alveolitis intensity, and CCL21 with lung function impairment.

Expression of HIF-1A/VEGF/ING-4 Axis in Pulmonary Sarcoidosis

Angiogenesis/angiostasis regulated by hypoxia inducible factor-1A (HIF-1A)/vascular endothelial growth factor (VEGF)/inhibitor of growth protein 4 (ING-4) axis may be crucial for the course and outcome of sarcoidosis. Overexpression of angiogenic factors (activation of VEGF through HIF-1A) may predispose to chronic course and lung fibrosis, whereas immunoangiostasis (related to an overexpression of inhibitory ING-4) may be involved in granuloma formation in early sarcoid inflammation, or sustained or recurrent formation of granulomas. In this work we investigated gene expression of HIF-1A, VEGF and ING-4 in bronchoalveolar fluid (BALF) cells and in peripheral blood (PB) lymphocytes of sarcoidosis patients (n=94), to better understand mechanisms of the disease and to search for its biomarkers. The relative gene expression level (RQ value) was analyzed by qPCR. The results were evaluated according to the presence of lung parenchymal involvement (radiological stage I vs. II-IV), acute vs. insidious onset, lung function tests, calcium metabolism parameters, percentage of lymphocytes (BALL%) and BAL CD4+/CD8+ in BALF, age, and gender. In BALF cells, the ING-4 and VEGF RQ values were increased, while HIF-1A expression was decreased. In PB lymphocytes all studied genes were overexpressed. Higher expression of HIF-1A in PB lymphocytes of patients with abnormal spirometry, and in BALF cells of patients with lung volume restriction was found. VEGF gene expression in BALF cells was also higher in patients with abnormal spirometry. These findings were in line with previous data on the role of HIF-1A/VEGF/ING-4 axis in the pathogenesis of sarcoidosis. Up-regulated HIF-1A and VEGF genes are linked to acknowledged negative prognostics.

Increased number and altered phenotype of lymphatic vessels in peripheral lung compartments of patients with COPD

BACKGROUND

De novo lymphatic vessel formation has recently been observed in lungs of patients with moderate chronic obstructive pulmonary disease (COPD). However, the distribution of lymphatic vessel changes among the anatomical compartments of diseased lungs is unknown. Furthermore, information regarding the nature of lymphatic vessel alterations across different stages of COPD is missing. This study performs a detailed morphometric characterization of lymphatic vessels in major peripheral lung compartments of patients with different severities of COPD and investigates the lymphatic expression of molecules involved in immune cell trafficking.

METHODS

Peripheral lung resection samples obtained from patients with mild (GOLD stage I), moderate-severe (GOLD stage II-III), and very severe (GOLD stage IV) COPD were investigated for podoplanin-immunopositive lymphatic vessels in distinct peripheral lung compartments: bronchioles, pulmonary blood vessels and alveolar walls. Control subjects with normal lung function were divided into never smokers and smokers. Lymphatics were analysed by multiple morphological parameters, as well as for their expression of CCL21 and the chemokine scavenger receptor D6.

RESULTS

The number of lymphatics increased by 133% in the alveolar parenchyma in patients with advanced COPD compared with never-smoking controls (p < 0.05). In patchy fibrotic lesions the number of alveolar lymphatics increased 20-fold from non-fibrotic parenchyma in the same COPD patients. The absolute number of lymphatics per bronchiole and artery was increased in advanced COPD, but numbers were not different after normalization to tissue area. Increased numbers of CCL21- and D6-positive lymphatics were observed in the alveolar parenchyma in advanced COPD compared with controls (p < 0.01). Lymphatic vessels also displayed increased mean levels of immunoreactivity for CCL21 in the wall of bronchioles (p < 0.01) and bronchiole-associated arteries (p < 0.05), as well as the alveolar parenchyma (p < 0.001) in patients with advanced COPD compared with never-smoking controls. A similar increase in lymphatic D6 immunoreactivity was observed in bronchioles (p < 0.05) and alveolar parenchyma (p < 0.01).

CONCLUSIONS

This study shows that severe stages of COPD is associated with increased numbers of alveolar lymphatic vessels and a change in lymphatic vessel phenotype in major peripheral lung compartments. This novel histopathological feature is suggested to have important implications for distal lung immune cell traffic in advanced COPD.