Organizing pneumonia in mice and men

Imaging of the Spectrum of Acute Lung Injury

Organizing pneumonia, acute fibrinous and organizing pneumonia, and diffuse alveolar damage, represent multi-compartment patterns of lung injury. The initial region of injury in all remains the same and is centered on the fused basement membrane (BM) between the capillary endothelium and type I pneumocyte. Injury leads to cellular death, BM denudation, increased cellular permeability, and BM structural damage, which leads to exudation, organization, and attempts at repair. When acute lung injury does lead to fibrosis, in some instances it can lead to histologic and/or radiologic usual interstitial pneumonia or nonspecific interstital pneumonia patterns suggesting that lung injury is the primary mechanism for the development of fibrosis.

Xuanfei Baidu Decoction reduces acute lung injury by regulating infiltration of neutrophils and macrophages via PD-1/IL17A pathway

The pathogenic hyper-inflammatory response has been revealed as the major cause of the severity and death of the Corona Virus Disease 2019 (COVID-19). Xuanfei Baidu Decoction (XFBD) as one of the "three medicines and three prescriptions" for the clinically effective treatment of COVID-19 in China, shows unique advantages in the control of symptomatic transition from moderate to severe disease states. However, the roles of XFBD to against hyper-inflammatory response and its mechanism remain unclear. Here, we established acute lung injury (ALI) model induced by lipopolysaccharide (LPS), presenting a hyperinflammatory process to explore the pharmacodynamic effect and molecular mechanism of XFBD on ALI. The in vitro experiments demonstrated that XFBD inhibited the secretion of IL-6 and TNF-α and iNOS activity in LPS-stimulated RAW264.7 macrophages. In vivo, we confirmed that XFBD improved pulmonary injury via down-regulating the expression of proinflammatory cytokines such as IL-6, TNF-α and IL1-β as well as macrophages and neutrophils infiltration in LPS-induced ALI mice. Mechanically, we revealed that XFBD treated LPS-induced acute lung injury through PD-1/IL17A pathway which regulates the infiltration of neutrophils and macrophages. Additionally, one major compound from XFBD, i.e. glycyrrhizic acid, shows a high binding affinity with IL17A. In conclusion, we demonstrated the therapeutic effects of XFBD, which provides the immune foundations of XFBD and fatherly support its clinical applications.

Mistaking Reversed Halo Sign with Cavity in Organizing Pneumonia: A Case Report

Organizing pneumonia (OP) is a rare inflammatory lung condition affecting bronchioles and alveoli. Symptoms may include cough, fever, malaise, fatigue, and weight loss with a wide variety of radiological manifestations. Both the unspecific symptoms and the radiological manifestations wide spectrum can make the diagnosis of OP challenging in daily practice. A pathological biopsy is a gold standard for diagnosis. However, there is usually a delay in making the diagnosis as a result of the time that is taken to decide to perform the biopsy. We present a case of OP in which its radiological manifestation first was mistaken for a cavity instead of the reversed halo sign (atoll sign) due to the similarity in some radiological features.

[Fibrotic remodeling of the lung following lung and stem-cell transplantation]

Transplantation of solid organs and hematopoietic stem cells represents an important therapeutic option for a variety of end-stage pulmonary diseases, aggressive hematopoietic neoplasms, or severe immunodeficiencies. Although the overall survival following transplantation has generally improved over recent decades, long-time survival of lung and stem-cell transplant recipients is still alarmingly low with an average 5‑year survival rate of only 50-60%. Chronic allo-immunoreactions in general and pulmonary allo-immunoreactions with subsequent fibrosis in particular are major reasons for this poor outcome. Comparable patterns of fibrotic lung remodeling are observed following both lung and hematopoietic stem-cell transplantation. Besides the meanwhile well-established obliterative and functionally obstructive remodeling of the small airways - obliterative bronchiolitis - a specific restrictive subform of fibrosis, namely alveolar fibroelastosis, has been identified. Despite their crucial impact on patient outcome, both entities can be very challenging to detect by conventional histopathological analysis. Their underlying mechanisms are considered overreaching aberrant repair attempts to acute lung injuries with overactivation of (myo-) fibroblasts and excessive and irreversible deposition of extracellular matrix. Of note, the underlying molecular mechanisms are widely divergent between these two morphological entities and are independent of the underlying clinical setting.Further comprehensive investigations of these fibrotic alterations are key to the development of much-needed predictive diagnostics and curative concepts, considering the high mortality of pulmonary fibrosis following transplantation.

Chronic interstitial pneumonia with features of organizing pneumonia in an adult horse

A 22-y-old American Quarter Horse gelding was presented with a history of chronic progressive respiratory problems and a diffuse pulmonary nodular pattern in thoracic radiographs. The horse was euthanized, and 4 formalin-fixed samples of lung were submitted for histopathology. There were multifocal areas of marked thickening of alveolar septa as a result of proliferation of myofibroblasts embedded in fibromyxoid matrix (interpreted as "Masson bodies"), focal areas of fibrosis, and numerous papillary projections of connective tissue into bronchioles. A diagnosis of organizing pneumonia was reached. No etiology was found for this lesion. It is important to consider causes of chronic interstitial pneumonia with fibrosis in horses other than equid herpesvirus 5, such as complicated viral or bacterial pneumonia or chronic toxicoses.

Hashimoto's thyroiditis-induced cryptogenic organizing pneumonia: A case report

A 49-year-old female patient developed chest tightness and shortness of breath without apparent cause and presented to a local hospital. Chest radiography indicated increased thickening of the lung texture, increased multiple patchy densities in the lower lobes of the bilateral lungs and a slightly enlarged thyroid. The patient was treated for pulmonary infection with antibiotics but the symptoms persisted. A repeated CT scan revealed ground-glass attenuation of the bilateral lungs with multiple flaky exudates and visible bronchogenic signs. The symptoms did not improve after broadening anti-microbial coverage. Bronchoscopy and biopsy confirmed cryptogenic organizing pneumonia (COP). Thyroid ultrasound and thyroid function tests jointly confirmed the diagnosis of Hashimoto's thyroiditis (HT). After receiving corticosteroid treatment, the patient's condition improved and she was discharged. This case demonstrates that COP may present in combination with Hashimoto's thyroiditis (HT) and may possibly even be caused by HT. Early confirmation of diagnosis and treatment will help to improve the prognosis of such patients.

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.

[Injury patterns in interstitial lung diseases]

Interstitial lung diseases (ILD) consist of a complex group of hundreds of non-neoplastic pulmonary diseases with divergent clinical presentation, morphology and progression tendency. This great number of clinical entities contrasts with a limited number of injury patterns. By definition, an adequate classification requires a synopsis of the clinical, radiological and morphological findings. The ATS/ERS (American Thoracic Society/ European Respiratory Society) guidelines recommend an open lung biopsy if high-resolution computed tomography does not provide conclusive results. Due to the focal nature and overlapping features of injury patterns, microscopic categorization is not always possible. In order to broaden the diagnostic criteria by using molecular patterns the Lung Research Working Group of the Institute of Pathology of Hannover Medical School, Europe's leading transplant center, is working up fresh explanted human lungs in a standardized manner. These fresh specimens are used for translational research by means of functional, morphological and molecular techniques in order to identify disease-specific regulatory processes and to make them usable diagnostically and therapeutically.

Cryptogenic Organizing Pneumonia Presenting as a Solitary Mass: Clinical, Imaging, and Pathologic Features

BACKGROUND Cryptogenic organizing pneumonia (COP), with a variety of radiologic findings, is a clinical pathological entity characterized by the presence of granulation tissue composed of fibroblasts/myofibroblasts and loose connective tissue in the alveoli and/or the distal bronchioles. Nevertheless, the presence of a solitary mass in COP is relatively rare. This study investigated the clinical, imaging, and pathologic features of COP with solitary mass form. MATERIAL AND METHODS This retrospective analysis included 12 patients (9 men and 3 women; age range 36-78 years; mean age 60±9 years) with surgery- or biopsy-proven COP with a solitary lung mass, diagnosed between June 2012 and December 2017 at the Department of Radiology in our hospital. RESULTS All patients experienced cough with expectoration and 8 patients had hemoptysis. All lesions were adjacent to the pleura. Mean size of the lesions was 4.2±0.9 cm (range, 3.2-6.1 cm). The upper left lobe was the site of the lesion in 4 patients. Six masses had heterogeneous density; among these, 4 had cavities and distal obstructive inflammation. The mass caused pleural indentation in 4 patients. Lymphadenopathy was seen in 7 patients. All specimens showed buds of granulation tissue within the lumen of the distal pulmonary airspaces, with significant increase in interstitial lymphocytes in 4 specimens. CONCLUSIONS Patients with COP with solitary mass form are more susceptible to hemoptysis and the mass is prone to necrosis. Vascular bundles, exudation around the mass, interstitial lymphocyte infiltration, and mediastinal lymph node enlargement are common features.

Long-Term Culture of Distal Airway Epithelial Cells Allows Differentiation Towards Alveolar Epithelial Cells Suited for Influenza Virus Studies

As the target organ for numerous pathogens, the lung epithelium exerts critical functions in health and disease. However, research in this area has been hampered by the quiescence of the alveolar epithelium under standard culture conditions. Here, we used human distal airway epithelial cells (DAECs) to generate alveolar epithelial cells. Long-term, robust growth of human DAECs was achieved using co-culture with feeder cells and supplementation with epidermal growth factor (EGF), Rho-associated protein kinase inhibitor Y27632, and the Notch pathway inhibitor dibenzazepine (DBZ). Removal of feeders and priming with DBZ and a cocktail of lung maturation factors prevented the spontaneous differentiation into airway club cells and instead induced differentiation to alveolar epithelial cells. We successfully transferred this approach to chicken distal airway cells, thus generating a zoonotic infection model that enables studies on influenza A virus replication. These cells are also amenable for gene knockdown using RNAi technology, indicating the suitability of the model for mechanistic studies into lung function and disease.

Exogenous alpha 1-antitrypsin down-regulates SERPINA1 expression

The main goal of the therapy with purified human plasma alpha1-antitrypsin (A1AT) is to increase A1AT levels and to prevent lungs from elastolytic activity in patients with PiZZ (Glu342Lys) A1AT deficiency-related emphysema. Potential hepatic gains of this therapy are unknown. Herein, we investigated the effect of A1AT therapy on SERPINA1 (gene encoding A1AT) expression. The expression of SERPINA1 was determined in A1AT or A1AT plus Oncostatin M (OSM) treated primary human hepatocytes isolated from liver tissues from A1AT deficient patients and control liver tissues. In addition, SERPINA1 mRNA was assessed in lung tissues from PiZZ emphysema patients with and without A1AT therapy, and in adherent human peripheral blood mononuclear cells (PBMC) isolated from healthy PiMM donors. In a dose-dependent manner purified A1AT lowered SERPINA1 expression in hepatocytes. This latter effect was more prominent in hepatocytes stimulated with OSM. Although it did not reach statistical significance (P = 0.0539)-analysis of lung tissues showed lower SERPINA1 expression in PiZZ emphysema patients receiving augmentation therapy relative to those without therapy. Finally, exogenously added purified A1AT (1mg/ml) reduced SERPINA1 expression in naïve as well as in lipopolysaccharide (LPS)-stimulated human adherent PBMCs. Exogenous A1AT protein reduces its own endogenous expression. Hence, augmentation with native M-A1AT protein and a parallel reduction in expression of dysfunctional mutant Z-A1AT may be beneficial for PiZZ liver, and this motivates further studies.

Radiation-Induced Organizing Pneumonia: A Characteristic Disease that Requires Symptom-Oriented Management

Radiation-induced organizing pneumonia (RIOP) is an inflammatory lung disease that is occasionally observed after irradiation to the breast. It is a type of secondary organizing pneumonia that is characterized by infiltrates outside the irradiated volume that are sometimes migratory. Corticosteroids work acutely, but relapse of pneumonia is often experienced. Management of RIOP should simply be symptom-oriented, and the use of corticosteroids should be limited to severe symptoms from the perspective not only of cost-effectiveness but also of cancer treatment. Once steroid therapy is started, it takes a long time to stop it due to frequent relapses. We review RIOP from the perspective of its diagnosis, epidemiology, molecular pathogenesis, and patient management.

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.