Obliterative airway remodelling in transplanted and non-transplanted lungs

Bioinformatics-based investigation on the genetic influence between SARS-CoV-2 infections and idiopathic pulmonary fibrosis (IPF) diseases, and drug repurposing

Some recent studies showed that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and idiopathic pulmonary fibrosis (IPF) disease might stimulate each other through the shared genes. Therefore, in this study, an attempt was made to explore common genomic biomarkers for SARS-CoV-2 infections and IPF disease highlighting their functions, pathways, regulators and associated drug molecules. At first, we identified 32 statistically significant common differentially expressed genes (cDEGs) between disease (SARS-CoV-2 and IPF) and control samples of RNA-Seq profiles by using a statistical r-package (edgeR). Then we detected 10 cDEGs (CXCR4, TNFAIP3, VCAM1, NLRP3, TNFAIP6, SELE, MX2, IRF4, UBD and CH25H) out of 32 as the common hub genes (cHubGs) by the protein-protein interaction (PPI) network analysis. The cHubGs regulatory network analysis detected few key TFs-proteins and miRNAs as the transcriptional and post-transcriptional regulators of cHubGs. The cDEGs-set enrichment analysis identified some crucial SARS-CoV-2 and IPF causing common molecular mechanisms including biological processes, molecular functions, cellular components and signaling pathways. Then, we suggested the cHubGs-guided top-ranked 10 candidate drug molecules (Tegobuvir, Nilotinib, Digoxin, Proscillaridin, Simeprevir, Sorafenib, Torin 2, Rapamycin, Vancomycin and Hesperidin) for the treatment against SARS-CoV-2 infections with IFP diseases as comorbidity. Finally, we investigated the resistance performance of our proposed drug molecules compare to the already published molecules, against the state-of-the-art alternatives publicly available top-ranked independent receptors by molecular docking analysis. Molecular docking results suggested that our proposed drug molecules would be more effective compare to the already published drug molecules. Thus, the findings of this study might be played a vital role for diagnosis and therapies of SARS-CoV-2 infections with IPF disease as comorbidity risk.

A first case of successful using of ibrutinib in treating paraneoplastic pemphigus related bronchiolitis obliterans concurrent with CLL

Paraneoplastic pemphigus (PNP) is a rare life-threatening disease which always associated with an underlying neoplasm. Tumor-related PNP most commonly precedes the detection of a hematological malignancy, with some cases seen during disease remission following cytotoxic drug therapy or radiotherapy. The lung is the most frequently-involved site in PNP, second only to the eyes, and involvement is seen in 59.2% to 92.8% of PNP cases. Bronchiolitis obliterans (BO) is the end stage of respiratory involvement and is regarded as life-threatening. The key point in treatment of PNP is to control the associated underlying hematologic neoplasia. High-dose systemic corticosteroids combined with other immunosuppressants are considered the first line of treatment. Other therapies that have shown beneficial effects include plasmapheresis, intravenous immunogloblin (IVIG), and more recently, daclizumab, alemtuzumab, and rituximab. There is no effective treatment for BO with PNP, and suppression of the cellular immune response may be necessary. Patients with PNP-BO associated with lymphoma mostly die within approximately 1 year. Herein, we reported a patient who diagnosed with PNP-BO concurrent with chronic lymphocytic leukemia. He was successful treated with ibrutinib and had achieved the longest survival which suggested that ibrutinib may be the best treatment choice for such patient.

Small airways dysfunction in patients with systemic sclerosis and interstitial lung disease

BACKGROUND

A number of studies report small airways involvement in patients with systemic sclerosis (SSc). Furthermore, small airways dysfunction is increasingly recognized in patients with interstitial lung disease (ILD) of idiopathic or autoimmune etiology. The objectives of this study were to evaluate small airways function in SSc patients with ILD and explore the effect of treatment on small airways function by using conventional and contemporary pulmonary function tests (PFTs).

METHODS

This single-center, prospective, observational study included a total of 35 SSc patients, with and without ILD based on HRCT scan, evaluated by a special radiologist blindly. Clinical data were collected from all patients who were also assessed for HRCT findings of small airways disease. Small airways function was assessed by classic spirometry, measurement of diffusing capacity for carbon monoxide, body plethysmography, single breath nitrogen washout (N2SBW) and impulse oscillometry (IOS). The prevalence of small airways dysfunction according to R5-R20, phase III slopeN2SBW and CV/VC methodologies was calculated in the total SSc population. Pulmonary function tests were compared between: (a) SSc-ILD and non-ILD patients and (b) two time points (baseline and follow up visit) in a subset of SSc-ILD patients who received treatment for ILD and were re-evaluated at a follow up visit after 12 months.

RESULTS

Phase III slopeN2SBW and R5-R20 showed the highest diagnostic performance for detecting small airways dysfunction among SSc patients (61 and 37.5%, respectively). Twenty three SSc patients were found with ILD and 14 of them had a 12-month follow up visit. SSc-ILD patients compared to those without ILD exhibited increased phase III slopeN2SBW ≥120% (p = 0.04), R5-R20 ≥0.07 kPa/L/s (p = 0.025), airway resistance (Raw) (p = 0.011), and special airway resistance (sRaw) (p = 0.02), and decreased specific airway conductance (sGaw) (p = 0.022), suggesting impaired small airways function in the SSc-ILD group. Radiographic features of SAD on HRCT were observed in 22% of SSc-ILD patients and in none of SSc-non-ILD patients. Comparison of PFTs between baseline and follow-up visit after 12 months in the 14 SSc-ILD treated patients, showed improvement of phase III slopeN2SBW (p = 0.034), R5-R20 (p = 0.035) and Raw (p = 0.044) but not sRaw and sGaw parameters.

CONCLUSION

Phase III slopeN2SBW and R5-R20 may reveal small airways dysfunction in SSc associated ILD before structural damage and may be partially improved in a subset of patients receiving treatment for ILD.

Morphological and molecular motifs of fibrosing pulmonary injury patterns

Interstitial lung diseases encompass a large number of entities, which are characterised by a small number of partially overlapping fibrosing injury patterns, either alone or in combination. Thus, the presently applied morphological diagnostic criteria do not reliably discriminate different interstitial lung diseases. We therefore analysed critical regulatory pathways and signalling molecules involved in pulmonary remodelling with regard to their diagnostic suitability. Using laser‐microdissection and microarray techniques, we examined the expression patterns of 45 tissue‐remodelling associated target genes in remodelled and non‐remodelled tissue samples from patients with idiopathic pulmonary fibrosis/usual interstitial pneumonia (IPF/UIP), non‐specific interstitial pneumonia (NSIP), organising pneumonia (OP) and alveolar fibroelastosis (AFE), as well as controls (81 patients in total). We found a shared usage of pivotal pathways in AFE, NSIP, OP and UIP, but also individual molecular traits, which set the fibrosing injury patterns apart from each other and correlate well with their specific morphological aspects. Comparison of the aberrant gene expression patterns demonstrated that (1) molecular profiling in fibrosing lung diseases is feasible, (2) pulmonary injury patterns can be discriminated with very high confidence on a molecular level (86–100% specificity) using individual gene subsets and (3) these findings can be adapted as suitable diagnostic adjuncts.

Precision medicine: integration of genetics and functional genomics in prediction of bronchiolitis obliterans after lung transplantation

PURPOSE OF REVIEW

Lung transplantation (LTx) can be a life saving treatment in end-stage pulmonary diseases, but survival after transplantation is still limited. Posttransplant development of chronic lung allograft dysfunction with bronchiolits obliterans syndrome (BOS) as the major subphenotype, is the main cause of morbidity and mortality. Early identification of high-risk patients for BOS is a large unmet clinical need. In this review, we discuss gene polymorphisms and gene expression related to the development of BOS.

RECENT FINDINGS

Candidate gene studies showed that donor and recipient gene polymorphisms affect transplant outcome and BOS-free survival after LTx. Both selective and nonselective gene expression studies revealed differentially expressed fibrosis and apoptosis-related genes in BOS compared with non-BOS patients. Significantly, recent microarray expression analysis of blood and broncho-alveolar lavage suggest a role for B-cell and T-cell responses prior to the development of BOS. Furthermore, 6 months prior to the development of BOS differentially expressed genes were identified in peripheral blood cells.

SUMMARY

Genetic polymorphisms and gene expression changes are associated with the development of BOS. Future genome wide studies are needed to identify easily accessible biomarkers for prediction of BOS toward precision medicine.

The activity of nintedanib in an animal model of allogenic left lung transplantation resembling aspects of allograft rejection

AIM OF THE STUDY

The prevention and treatment of chronic lung allograft dysfunction (CLAD) after lung transplantation (LTx) remain unsatisfactory. Growth factors may play an important role in the development of CLAD. This study evaluated the effects of nintedanib, a receptor tyrosine kinase inhibitor, in the treatment of CLAD after experimental LTx.

MATERIALS AND METHODS

A rat model of left lung allo-transplantation (Fisher 344 to Wistar Kyoto) was used to evaluate the effect of nintedanib (50 mg/kg per day) on the development of CLAD. Therapy with nintedanib began 2 days before LTx and ended on postoperative day (POD) 20 (n = 6) or 60 (n = 6). Nontreated animals who underwent LTx (n = 12) were used as controls, whereas naïve lungs (n = 24) served as reference for physiological healthy organs without transplantation damage or medical effects. Acute and chronic rejection were evaluated on POD 20 and 60, respectively.

RESULTS

Immunohistologic analysis showed a decrease in growth factors/receptors on POD 60 (nintedanib-treated vs. nontreated controls: platelet-derived growth factor (PDGF) A: [P ≤ 0.001]; PDGF receptor-α: [P ≤ 0.001]; vascular endothelial growth factor (VEGF) A: [P ≤ 0.001]; VEGF receptor-2: [P ≤ 0.001]). However, no reductions in fibrotic changes were observed in nintedanib-treated allografts compared with nontreated allografts. Although nintedanib treatment started before LTx none of the animals showed impaired wound healing. No dehiscence of the sutures of the bronchus, vessels or skin, or stenosis of the bronchus was found.

CONCLUSION

In conclusion, while nintedanib reduced the expression of growth factors/receptors in a rat LTx model, a reduction in fibrotic alterations was not observed at POD 60.

Repeated systemic administration of adipose tissue-derived mesenchymal stem cells prevents tracheal obliteration in a murine model of bronchiolitis obliterans

OBJECTIVE

To investigate the effect of adipose tissue-derived mesenchymal stem cell (ASC) administered either systemically or locally in a murine model of bronchiolitis obliterans.

RESULTS

When compared to controls, systemic treatment with 10⁶ ASCs on D0 and a second dose on D7 significantly prevented tracheal obliteration 28 days after heterotopic tracheal transplantation (median of 94 vs. 16%; P < 0.01). A single dose tended towards less stenosis than controls, but did not reach statistical significance (28 vs. 94%; P = 0.054). On the contrary, repeated local injection was incapable of preventing tracheal obliteration when compared to a single injection or controls (37 vs. 71 vs. 87%). Two intravenous doses also tended to be better than two local injections (16 vs. 37%; P = 0.058), and were better than a single local dose (16 vs. 71%; P < 0.01).

CONCLUSION

A second dose of ASC, given systemically after 7 days, reduces luminal obliteration in a heterotopic tracheal transplantation model in mice, suggesting that ASC can be used to prevent obliterative bronchiolitis after lung transplantation.

Comparative analysis of morphological and molecular motifs in bronchiolitis obliterans and alveolar fibroelastosis after lung and stem cell transplantation

Chronic lung allograft dysfunction (CLAD) remains the major obstacle to long‐term survival following lung transplantation (LuTx). Morphologically CLAD is defined by obliterative remodelling of the small airways (bronchiolitis obliterans, BO) as well as a more recently described collagenous obliteration of alveoli with elastosis summarised as alveolar fibroelastosis (AFE). Both patterns are not restricted to pulmonary allografts, but have also been reported following haematopoietic stem cell transplantation (HSCT) and radio chemotherapy (RC). In this study we performed compartment‐specific morphological and molecular analysis of BO and AFE lesions in human CLAD (n = 22), HSCT (n = 29) and RC (n = 6) lung explants, utilising conventional histopathology, laser‐microdissection, PCR techniques and immunohistochemistry to assess fibrosis‐associated gene and protein expression. Three key results emerged from our analysis of fibrosis‐associated genes: (i) generally speaking, “BO is BO”. Despite the varying clinical backgrounds, the molecular characteristics of BO lesions were found to be alike in all groups. (ii) “AFE is AFE”. In all groups of patients suffering from restrictive changes to lung physiology due to AFE there were largely – but not absolutely ‐ identical gene expression patterns. iii) BO concomitant to AFE after LuTx is characterised by an AFE‐like molecular microenvironment, representing the only exception to (i). Additionally, we describe an evolutionary model for the AFE pattern: a non‐specific fibrin‐rich reaction to injury pattern triggers a misguided resolution attempt and eventual progression towards manifest AFE. Our data point towards an absence of classical fibrinolytic enzymes and an alternative fibrin degrading mechanism via macrophages, resulting in fibrous remodelling and restrictive functional changes. These data may serve as diagnostic adjuncts and help to predict the clinical course of respiratory dysfunction in LuTx and HSCT patients. Moreover, analysis of the mechanism of fibrinolysis and fibrogenesis may unveil potential therapeutic targets to alter the course of the eventually fatal lung remodelling.

Airway remodelling in the transplanted lung

Following lung transplantation, fibrotic remodelling of the small airways has been recognized for almost 5 decades as the main correlate of chronic graft failure and a major obstacle to long-term survival. Mainly due to airway fibrosis, pulmonary allografts currently show the highest attrition rate of all solid organ transplants, with a 5-year survival rate of 58 % on a worldwide scale. The observation that these morphological changes are not just the hallmark of chronic rejection but rather represent a manifestation of a multitude of alloimmune-dependent and -independent injuries was made more recently, as was the discovery that chronic lung allograft dysfunction manifests in different clinical phenotypes of respiratory impairment and corresponding morphological subentities. Although recent years have seen considerable advances in identifying and categorizing these subgroups on the basis of clinical, functional and histomorphological changes, as well as susceptibility to medicinal treatment, this process is far from over. Since the actual pathophysiological mechanisms governing airway remodelling are still only poorly understood, diagnosis and therapy of chronic lung allograft dysfunction presents a major challenge to clinicians, radiologists and pathologists alike. Here, we review and discuss the current state of the literature on chronic lung allograft dysfunction and shed light on classification systems, corresponding clinical and morphological changes, key cellular players and underlying molecular pathways, as well as on emerging diagnostic and therapeutic approaches.

Organizing pneumonia in mice and men

BACKGROUND

Organizing pneumonia is a reaction pattern and an inflammatory response to acute lung injuries, and is characterized by intraluminal plugs of granulation tissue in distal airspaces. In contrast to other fibrotic pulmonary diseases, organizing pneumonia is generally responsive to corticosteroids. However, some patients do not respond to treatment, leading to respiratory failure and potentially death (up to 15 % of patients). In order to devise new therapeutic strategies, a better understanding of the disease's pathomechanisms is warranted. We previously generated a mouse model overexpressing CCL2, which generates organizing pneumonia-like changes, morphologically comparable to human patients. In this study, we investigated whether the histopathological similarities of human and murine pulmonary organizing pneumonia lesions also involve similar molecular pathways.

METHODS

We analyzed the similarities and differences of fibrosis-associated gene expression in individual compartments from patients with organizing pneumonia and transgenic (CCL2) mice using laser-assisted microdissection, real-time PCR and immunohistochemistry.

RESULTS

Gene expression profiling of human and murine organizing pneumonia lesions showed in part comparable expression levels of pivotal genes, notably of TGFB1/Tgfb1, TIMP1/Timp1, TIMP2/Timp2, COL3A1/Col3a1, CXCL12/Cxcl12, MMP2/Mmp2 and IL6/Il6. Hence, the transgenic CCL2 mouse model shows not only pathogenomic and morphological features of human organizing pneumonia but also a similar inflammatory profile.

CONCLUSIONS

We suggest that the CCL2-overexpressing transgenic mouse model (CCL2 Tg mice) is suitable for further investigation of fibrotic pulmonary remodeling, particularly of organizing pneumonia pathogenesis and for the search for novel therapeutic strategies.

Molecular Profiling in Lung Biopsies of Human Pulmonary Allografts to Predict Chronic Lung Allograft Dysfunction

Chronic lung allograft dysfunction (CLAD) is the main reason for poor long-term outcome of lung transplantation, with bronchiolitis obliterans (BO) representing the predominant pathological feature. BO is defined as a progressive fibrous obliteration of the small airways, thought to be triggered by a combination of nonimmune bronchial injury and alloimmune and autoimmune mechanisms. Because biopsy samples are too insensitive to reliably detect BO and a decline in lung function test results, which is clinically used to define CLAD, does not detect early stages, there is need for alternative biomarkers for early diagnosis. Herein, we analyzed the cellular composition and differential expression of 45 tissue remodeling-associated genes in transbronchial lung biopsy specimens from two cohorts with 18 patients each: patients who did not develop CLAD within 3 years after transplantation (48 biopsy specimens) and patients rapidly developing CLAD within the first 3 postoperative years (57 biopsy specimens). Integrating the mRNA expression levels of the five most significantly dysregulated genes from the transforming growth factor-β axis (BMP4, IL6, MMP1, SMAD1, and THBS1) into a score, patient groups could be confidently separated and the outcome predicted (P < 0.001). We conclude that overexpression of fibrosis-associated genes may be valuable as a tissue-based molecular biomarker to more accurately diagnose or predict the development of CLAD.

[Aberrant reparative tissue remodeling: histopathology and molecular pathology]

Not only tumorous infiltrations can lead to destruction of parenchymal organs but also the aberrant proliferation and matrix production of mesenchymal cells and vessels during a dysregulated repair attempt. This fibrogenesis is the result of a complex pathogenesis, which can be investigated in animal models but also in situ to harvest new biomarkers. This article deals particularly with the second method and summarizes molecular pathological findings in various model diseases for aberrant reparative tissue reconstruction. These model diseases include plexiform vasculopathy in pulmonary arterial hypertension (PAH), Quilty lesions in heart transplantation, bronchiolitis obliterans (BO), inflammatory airway remodeling and Epstein-Barr virus (EBV) induced smooth muscle proliferation (posttransplantation smooth muscle tumor, PTSMT).Using in situ molecular pathology, we were able to dismiss an assumed involvement of myofibroblastic cells in vessel reconstruction of the lung in PAH. We could also for the first time perform a comprehensive molecular characterization of the vascular remodeling and prove that plexiform vasculopathy represents a complex-regulated epiphenomenon of excessive pulmonary hypertension. This method also allowed us to describe for the first time the miRNA expression in PAH in a compartment-specific manner and to draw conclusions regarding the damaged overriding regulatory mechanisms. In the same way, we were also able to describe the chimeric character of the complex neoangiogenesis in the donor organ after heart transplantation.After lung transplantation, we identified for the first time a group of tissue-based molecular markers, which can predict later occurrence of BO even in morphologically normal transbronchial biopsies. In addition, we have documented for the first time the molecular characteristics of the morphologically analogous airway reconstruction in lung-transplanted and non-transplanted patients. We could further elucidate the role of matrix metalloproteinases (MMP) and their antagonists in inflammatory airway reconstruction and deduce from this the resulting therapeutic implications. Accordingly, we were able to further clarify the origin, pathogenesis and the malignant potential of EBV-induced PTSMT and for the first time provide an evidence-based therapy recommendation and risk assessment.In summary, this article documents that in situ diagnostics can meet the requirements of the challenging parameters and issues of life sciences. It is to be expected that the technical possibilities will develop analogously to the increasing demands and the in situ method will move further into the focus of molecular pathology.

WNT7B in fibroblastic foci of idiopathic pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a devastating interstitial pneumonia causing a loss of respiratory surface area due to a proliferative fibrotic response involving hyperplastic, hypertrophic, and metaplastic epithelium, cystic honeycomb change, septal expansion, and variable inflammation. Wnt (wingless) signaling glycoproteins are known to be involved in lung development and tissue repair, and are up-regulated in patients with IPF. Based on previous qRT-PCR data showing increased Wnt7B in lungs of IPF patients, a systematic, quantitative examination of its tissue site distribution was undertaken.

Methods

Tissue samples from the Lung Tissue Research Consortium (LTRC) of 39 patients diagnosed with mild to severe IPF/usual interstitial pneumonia (UIP) and 19 normal patients were examined for the immunolocalization of Wnt7B.

Results

In normal lung, moderate Wnt7B reactivity was confined to airway epithelium, smooth muscle of airways and vasculature, and macrophages. IPF lung showed strong Wnt7B reactivity in fibroblastic foci, dysplastic airway and alveolar epithelium, and in highly discrete subepithelial, basement membrane-associated regions. All reactive sites were sized and counted relative to specific microscopic regions. Those in the subepithelial sites were found in significantly greater numbers and larger relative area compared with the others. No reactive sites were present in normal patient controls.

Conclusions

The results demonstrate Wnt7B to be expressed at high concentrations in regions of active hyperplasia, metaplasia, and fibrotic change in IPF patients. In this context and its previously established biologic activities, Wnt7B would be expected to be of potential importance in the pathogenesis of IPF.

Krüppel-like zinc finger proteins in end-stage COPD lungs with and without severe alpha1-antitrypsin deficiency

Background

Chronic obstructive pulmonary disease (COPD) is influenced by environmental and genetic factors. An important fraction of COPD cases harbor a major genetic determinant, inherited ZZ (Glu342Lys) α1-antitrypsin deficiency (AATD). A study was undertaken to investigate gene expression patterns in end-stage COPD lungs from patients with and without AATD.

Methods

Explanted lungs of end-stage ZZ AATD-related (treated and non-treated with AAT augmentation therapy) and “normal” MM COPD, and liver biopsies from patients suffering from liver cirrhosis with and without ZZ AATD were used for gene expression analysis by Affymetrix microarrays or RT-PCR.

Results

A total of 162 genes were found to be differentially expressed (p-value ≤ 0.05 and |FC| ≥ 2) between MM and ZZ COPD patients. Of those, 134 gene sets were up-regulated and 28 were down-regulated in ZZ relative to MM lung tissue. A subgroup of genes, zinc finger protein 165, snail homolog 1 (Drosophila) (SNAI1), and Krüppel-like transcription factors (KLFs) 4 (gut), 9 and 10, perfectly segregated ZZ and MM COPD patients. The higher expression of KLF 9 and KLF10 has been verified in the replication cohort with AATD-related end-stage lung emphysema and liver cirrhosis. Furthermore, higher expression of KLF9, SNAI1 and DEFA1 was found in ZZ COPD lungs without augmentation therapy relative to MM COPD or ZZ COPD with augmentation therapy.

Conclusions

These results reveal the involvement of transcriptional regulators of the zinc-finger family in COPD pathogenesis and provide deeper insight into the pathophysiological mechanisms of COPD with and without AATD.

Bronchiolitis and bronchial disorders in interstitial lung disease

PURPOSE OF REVIEW

Bronchial and bronchiolar abnormalities in interstitial lung diseases (ILDs) are an issue often underestimated. However, new interstitial patterns with bronchiolar involvement are being described and the concept is still evolving. The scope of this review is to introduce a comprehensive approach to airway disorders in the context of ILDs, mainly from a pathologic perspective.

RECENT FINDINGS

Recent studies have revealed significant inflammatory and structural alterations at the level of small airways in idiopathic interstitial pneumonias, which may participate in the lung-remodeling pathogenetic process. A suggested pathogenetic role of cigarette smoking for lung-remodeling in smoking-related ILDs is further investigated, and unclassified fibrosis as a prominent feature in lung biopsy specimens of smokers has been established. New targeted therapies for lymphangioleiomyomatosis based on molecular and biologic properties of the disease are currently undergoing clinical trials. Combined pharmaceutical and interventional therapeutic regimens are of growing concern for refractory airway lesions in sarcoidosis. The application of volumetric high-resolution computed tomography (HRCT) chest scanning with acquisition of expiratory images provides valuable information about the involvement of small airways in ILDs.

SUMMARY

The imaging and pathologic focus on airway abnormalities in ILDs make them an integral part of their pathology with a significant pathogenetic role in interstitial processes and variable contribution to the functional status of patients.

Obliterative airway remodeling: molecular evidence for shared pathways in transplanted and native lungs

Obliteration of the small airways is a largely unresolved challenge in pulmonary medicine. It represents either the irreversible cause of functional impairment or a morphologic disorder of limited importance in a multitude of diseases. Bronchiolitis obliterans is a key complication of lung transplantation. No predictive markers for the onset of obliterative remodeling are currently available. To further elucidate the molecular mechanisms of airway remodeling, compartment-specific expression patterns were analyzed in patients. For this purpose, remodeled and nonremodeled bronchioli were isolated from transplanted and nontransplanted lung explants using laser-assisted microdissection (n = 24). mRNA expression of 45 fibrosis-associated genes was measured using quantitative real-time RT-PCR. For 20 genes, protein expression was also analyzed by immunohistochemistry. Infiltrating cells were characterized at conventional histology and immunohistochemistry. Obliterative remodeling of the small airways in transplanted and nontransplanted lungs shared similar grades of chronic inflammation and pivotal fibrotic pathways such as transforming growth factor β signaling and increased collagen expression. Bone morphogenetic protein and thrombospondin signaling, and also matrix metalloproteinases and tissue inhibitor of metalloproteinases, were primarily up-regulated in obliterative airway remodeling in nontransplanted lungs. In transplanted lungs, clinical remodeled bone morphogenetic protein but nonremodeled bronchioli were characterized by a concordant up-regulation of matrix metalloproteinase-9, RANTES, and tissue inhibitor of metalloproteinase-1. These distinct expression patterns warrant further investigation as potential markers of impending airway remodeling, especially for prospective longitudinal molecular profiling.

Plexiform lesions in pulmonary arterial hypertension composition, architecture, and microenvironment

Pulmonary arterial hypertension (PAH) is a debilitating disease with a high mortality rate. A hallmark of PAH is plexiform lesions (PLs), complex vascular formations originating from remodeled pulmonary arteries. The development and significance of these lesions have been debated and are not yet fully understood. Some features of PLs resemble neoplastic disorders, and there is a striking resemblance to glomeruloid-like lesions (GLLs) in glioblastomas. To further elucidate PLs, we used in situ methods, such as (fluorescent) IHC staining, three-dimensional reconstruction, and laser microdissection, followed by mRNA expression analysis. We generated compartment-specific expression patterns in the lungs of 25 patients (11 with PAH associated with systemic shunts, 6 with idiopathic PAH, and 8 controls) and GLLs from 5 glioblastomas. PLs consisted of vascular channels lined by a continuously proliferating endothelium and backed by a uniform myogenic interstitium. They also showed up-regulation of remodeling-associated genes, such as HIF1a, TGF-β1, VEGF-α, VEGFR-1/-2, Ang-1, Tie-2, and THBS1, but also of cKIT and sprouting-associated markers, such as NOTCH and matrix metalloproteinases. The cellular composition and signaling seen in GLLs in neural neoplasms differed significantly from those in PLs. In conclusion, PLs show a distinct cellular composition and microenvironment, which contribute to the plexiform phenotype and set them apart from other processes of vascular remodeling in patients with PAH. Neoplastic models of angiogenesis seem to be of limited use in further study of plexiform vasculopathy.