Neutrophil extracellular traps induce the epithelial-mesenchymal transition: implications in post-COVID-19 fibrosis

The release of neutrophil extracellular traps (NETs), a process termed NETosis, avoids pathogen spread but may cause tissue injury. NETs have been found in severe COVID-19 patients, but their role in disease development is still unknown. The aim of this study is to assess the capacity of NETs to drive epithelial-mesenchymal transition (EMT) of lung epithelial cells and to analyze the involvement of NETs in COVID-19. Neutrophils activated with PMA (PMA-Neu), a stimulus known to induce NETs formation, induce both EMT and cell death in the lung epithelial cell line, A549. Notably, NETs isolated from PMA-Neu induce EMT without cell damage. Bronchoalveolar lavage fluid of severe COVID-19 patients showed high concentration of NETs. Thus, we tested in an in vitro alveolar model the hypothesis that virus-induced NET may drive EMT. Co-culturing A549 at air-liquid interface with alveolar macrophages, neutrophils and SARS-CoV2, we demonstrated a significant induction of the EMT in A549 together with high concentration of NETs, IL8 and IL1{beta}, best-known inducers of NETosis. Lung tissues of COVID-19 deceased patients showed that epithelial cells are characterized by increased mesenchymal markers. These results show for the first time that NETosis plays a major role in triggering lung fibrosis in COVID-19 patients.

Clinical presentation and evolution of COVID-19 in immunosuppressed patients. Preliminary evaluation in a North Italian cohort on calcineurin-inhibitors based therapy

The clinical course of COVID-19 in patients undergoing chronic immunosuppressive therapy is yet poorly known. We performed a monocentric cross-sectional study describing the clinical course of COVID-19 in a cohort of patients from northern Italy treated with calcineurin-inhibitors for organ transplantation or rheumatic diseases. Data were collected by phone call and clinical chart review between March 27th- 31st 2020. COVID-19 related symptoms, rynopharingeal swab, therapeutic changes and outcome were assessed in 384 consecutive patients (57% males; median age 61 years, IQR 48-69). 331 patients (86%) received solid organ transplantation (kidney n=140, 36%, heart n=100, 26%, lung n=91, 24%) and 53 (14%) had a rheumatic disease. Calcineurin inhibitors were the only immunosuppressant administered in 46 patients (12%). 14 patients developed a "confirmed COVID-19" (swab positivity) and 14 a "clinical COVID-19" (only typical symptoms). Fever (75%) and diarrhoea (50%) were the most common symptoms. Fourteen patients were hospitalized and 11 have already been dismissed. No patient required start/changes of the O2 therapy or developed superinfection. Only one patient, with metastatic lung cancer, died. In conclusion, COVID-19 showed a mild course in our cohort, with low mortality. Calcineurin inhibitor-based immunosuppressive regimens appear safe in this context and should not be discontinued.