Time-dependent molecular motifs of pulmonary fibrogenesis in COVID-19

Background: In COVID-19 survivors, there is an increased prevalence of pulmonary fibrosis of which the underlying molecular mechanisms are poorly understood. Aims and objectives: In this study, we aimed to gain insights into the evolution of pulmonary fibrogenesis in COVID19. Method(s): In this multicentric study, n=12 patients who succumbed to COVID-19 due to progressive respiratory failure were assigned to an early and late group (death within <=7 and >7 days of hospitalization, respectively) and compared to n=11 healthy controls;mRNA and protein expression were analyzed using a fibrosis-specific panel and immunostaining. Biological pathway analysis was performed using two different gene expression databases. Result(s): Median duration of hospitalization until death was 3 (IQR25-75, 3-3.75) and 14 (12.5-14) days in the early and late group, respectively. Fifty-eight out of 770 analyzed genes showed a significantly altered expression signature in COVID-19 compared to controls in a time-dependent manner. The entire study group showed an increased expression of Bone Marrow Stromal Cell Antigen 2 (BST2) and interleukin-1 receptor 1 (IL1R1), independent of hospitalization time. In the early group, there was increased activity of inflammation-related genes and pathways, while fibrosis-related genes (particularly PDGFRB) and pathways dominated in the late group. Conclusion(s): After the first week of hospitalization, there is a shift from pro-inflammatory to fibrogenic activity in severe COVID-19. IL1R1 and PDGFRB may serve as potential therapeutic targets in future studies.

COVID-19 is a systemic vascular hemopathy: insight for mechanistic and clinical aspects

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is presenting as a systemic disease associated with vascular inflammation and endothelial injury. Severe forms of SARS-CoV-2 infection induce acute respiratory distress syndrome (ARDS) and there is still an ongoing debate on whether COVID-19 ARDS and its perfusion defect differs from ARDS induced by other causes. Beside pro-inflammatory cytokines (such as interleukin-1 beta [IL-1beta] or IL-6), several main pathological phenomena have been seen because of endothelial cell (EC) dysfunction: hypercoagulation reflected by fibrin degradation products called D-dimers, micro- and macrothrombosis and pathological angiogenesis. Direct endothelial infection by SARS-CoV-2 is not likely to occur and ACE-2 expression by EC is a matter of debate. Indeed, endothelial damage reported in severely ill patients with COVID-19 could be more likely secondary to infection of neighboring cells and/or a consequence of inflammation. Endotheliopathy could give rise to hypercoagulation by alteration in the levels of different factors such as von Willebrand factor. Other than thrombotic events, pathological angiogenesis is among the recent findings. Overexpression of different proangiogenic factors such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-2) or placental growth factors (PlGF) have been found in plasma or lung biopsies of COVID-19 patients. Finally, SARS-CoV-2 infection induces an emergency myelopoiesis associated to deregulated immunity and mobilization of endothelial progenitor cells, leading to features of acquired hematological malignancies or cardiovascular disease, which are discussed in this review. Altogether, this review will try to elucidate the pathophysiology of thrombotic complications, pathological angiogenesis and EC dysfunction, allowing better insight in new targets and antithrombotic protocols to better address vascular system dysfunction. Since treating SARS-CoV-2 infection and its potential long-term effects involves targeting the vascular compartment and/or mobilization of immature immune cells, we propose to define COVID-19 and its complications as a systemic vascular acquired hemopathy. Copyright © 2021, The Author(s), under exclusive licence to Springer Nature B.V.

ENDOGENOUS REGULATION OF NEUTROPHIL EXTRACELLULAR TRAPS IN ACUTE ISCHAEMIC STROKE DUE TO VACCINE-INDUCED IMMUNE THROMBOTIC THROMBOCYTOPENIA

Background and aims: Vaccination is one of the most important countermeasures in the ongoing COVID19-pandemic. Pharmacovigilance concerns, however, emerged after very rare, but potentially disastrous thrombotic complications following vaccination with ChAdOx1. The underlying pathology was described as platelet factor 4 antibody mediated vaccine-induced immune thrombotic thrombocytopenia (VITT). Mechanisms of immunothrombosis including the regulation of neutrophil extracellular traps (NETs) might be of crucial importance in VITT. Methods: In this study, we had the exceptional opportunity to investigate blood and thrombus samples of a patient who suffered severe ischaemic stroke due to VITT undergoing successful mechanical thrombectomy (MT) in comparison to 13 control stroke patients with similar clinical characteristics without VITT. Cerebral thrombi were stained for complement factors, NETs-markers, DNase and LL-37 and were histologically assessed. In blood samples before MT and 7 days later, cell-free DNA, myeloperoxidase-histone complexes, myeloperoxidase activity, DNase activity, LL-37 and inflammatory cytokines were determined. Results: We identified NETs-markers in thrombi of all patients. The thrombus of the VITT-patient, however, exclusively revealed complement factors and high amounts of NETs-degrading DNase and LL-37, which protects NETs from degradation. In accordance, ex vivo and in vitro studies also implied a disturbed regulation of NETs in VITT-samples. Moreover, we found markedly pronounced temporal changes of specific circulating cytokines in the VITT-case. Conclusions: The results of this study suggest a disturbed endogenous regulation of NETs in VITT involving a pro-inflammatory response and fulminant clinical course. Further studies are warranted to confirm our results and to provide deeper insights into the causative mechanisms.

Imaging intact human organs with local resolution of cellular structures using hierarchical phase-contrast tomography.

Imaging intact human organs from the organ to the cellular scale in three dimensions is a goal of biomedical imaging. To meet this challenge, we developed hierarchical phase-contrast tomography (HiP-CT), an X-ray phase propagation technique using the European Synchrotron Radiation Facility (ESRF)'s Extremely Brilliant Source (EBS). The spatial coherence of the ESRF-EBS combined with our beamline equipment, sample preparation and scanning developments enabled us to perform non-destructive, three-dimensional (3D) scans with hierarchically increasing resolution at any location in whole human organs. We applied HiP-CT to image five intact human organ types: brain, lung, heart, kidney and spleen. HiP-CT provided a structural overview of each whole organ followed by multiple higher-resolution volumes of interest, capturing organotypic functional units and certain individual specialized cells within intact human organs. We demonstrate the potential applications of HiP-CT through quantification and morphometry of glomeruli in an intact human kidney and identification of regional changes in the tissue architecture in a lung from a deceased donor with coronavirus disease 2019 (COVID-19).

Clinical and molecular practice of European thoracic pathology laboratories during the COVID-19 pandemic. The past and the near future.

BACKGROUND: This study evaluated the consequences in Europe of the COVID-19 outbreak on pathology laboratories orientated toward the diagnosis of thoracic diseases. MATERIALS AND METHODS: A survey was sent to 71 pathology laboratories from 21 European countries. The questionnaire requested information concerning the organization of biosafety, the clinical and molecular pathology, the biobanking, the workload, the associated research into COVID-19, and the organization of education and training during the COVID-19 crisis, from 15 March to 31 May 2020, compared with the same period in 2019. RESULTS: Questionnaires were returned from 53/71 (75%) laboratories from 18 European countries. The biosafety procedures were heterogeneous. The workload in clinical and molecular pathology decreased dramatically by 31% (range, 3%-55%) and 26% (range, 7%-62%), respectively. According to the professional category, between 28% and 41% of the staff members were not present in the laboratories but did teleworking. A total of 70% of the laboratories developed virtual meetings for the training of residents and junior pathologists. During the period of study, none of the staff members with confirmed COVID-19 became infected as a result of handling samples. CONCLUSIONS: The COVID-19 pandemic has had a strong impact on most of the European pathology laboratories included in this study. Urgent implementation of several changes to the organization of most of these laboratories, notably to better harmonize biosafety procedures, was noted at the onset of the pandemic and maintained in the event of a new wave of infection occurring in Europe.