ABSTRACT
The development of lung fibrosis is a major concern in patients recovered from severe COVID-19 pneumonia. This study aimed to document the evolution of diffuse alveolar damage (DAD) to the fibrosing pattern and define the transcriptional programs involved. Morphological, immunohistochemical and transcriptional analysis were performed in lung samples obtained from autopsy of 33 severe COVID-19 patients (median illness duration: 36 days). Normal lung and idiopathic pulmonary fibrosis (IPF) were used for comparison. Twenty-seven patients with DAD and disease evolution of more than 2 weeks had fibrosis. Pathways and genes related with collagen biosynthesis and extracellular matrix (ECM) biosynthesis and degradation, myofibroblastic differentiation and epithelial to mesenchymal transition (EMT) were overexpressed in COVID-19. This pattern had similarities with that observed in IPF. By immunohistochemistry, pathological fibroblasts (pFBs), with CTHRC1 and SPARC expression, increased in areas of proliferative DAD and decreased in areas of mature fibrosis. Immunohistochemical analysis demonstrated constitutive expression of cadherin-11 in normal epithelial cells and a similar pattern of cadherin and catenin expression in epithelial cells from both normal and COVID-19 samples. Transcriptomic analysis revealed downregulation of the Hippo pathway, concordant with the observation of YAP overexpression in hyperplastic alveolar epithelial cells. Progression to fibrosis in severe COVID-19 is associated with overexpression of fibrogenic pathways and increased in CTHRC1- and SPARC-positive pFBs. Whereas the Hippo pathway seemed to be implicated in the response to epithelial cell damage, EMT was not a major process implicated in COVID-19 mediated lung fibrosis.
ABSTRACT
CASE PRESENTATION: An 84-year-old man with an active smoking habit presented to the ED with dyspnea, hemoptysis, and thick phlegm that was difficult to clear. He reported no weight loss, no fever, and no chest pain or dysphonia. He denied both international travel and previous contact with confirmed cases of TB or SARS-CoV-2. He had no known occupational exposures. The patient's personal history included a resolved complete atrioventricular block that required a permanent pacemaker, moderate-to-severe COPD, rheumatoid arthritis (treated with oral prednisone, 2.5 mg/d) and B-chronic lymphocytic leukemia (treated with methotrexate and prophylactic oral supplements of ferrous sulfate). Moreover, he was in medical follow up because of a peptic ulcer, atrophic gastritis, and colonic diverticulosis. The patient also had a history of thoracic surgery after an episode of acute mediastinitis from an odontogenic infection, which required ICU management and temporal tracheostomy.
Subject(s)
Bronchoscopy/methods , COVID-19/diagnosis , Ferrous Compounds , Lung Diseases , Multiple Chronic Conditions/therapy , Respiratory Aspiration , Aged, 80 and over , Biopsy/methods , Bronchoalveolar Lavage/methods , COVID-19/epidemiology , Diagnosis, Differential , Ferrous Compounds/administration & dosage , Ferrous Compounds/adverse effects , Hematinics/administration & dosage , Hematinics/adverse effects , Hemoptysis/diagnosis , Hemoptysis/etiology , Humans , Lung Diseases/chemically induced , Lung Diseases/diagnostic imaging , Lung Diseases/physiopathology , Lung Diseases/therapy , Male , Respiratory Aspiration/complications , Respiratory Aspiration/diagnosis , Respiratory Aspiration/physiopathology , SARS-CoV-2 , Tomography, X-Ray Computed/methods , Withholding TreatmentABSTRACT
Diffuse alveolar damage and thrombi are the most common lung histopathological lesions reported in patients with severe COVID-19. Although some studies have suggested increased pulmonary angiogenesis, the presence of vascular proliferation in COVID-19 lungs has not been well characterised. Glomeruloid-like microscopic foci and/or coalescent vascular proliferations measuring up to 2 cm were present in the lung of 14 out of 16 autopsied patients. These lesions expressed CD31, CD34 and vascular endothelial cadherin. Platelet-derived growth factor receptor-ß immunohistochemistry and dual immunostaining for CD34/smooth muscle actin demonstrated the presence of pericytes. These vascular alterations may contribute to the severe and refractory hypoxaemia that is common in patients with severe COVID-19.