Circulating markers of extracellular matrix remodelling in severe COVID-19 patients.

BACKGROUND: Abnormal remodelling of the extracellular matrix (ECM) has generally been linked to pulmonary inflammation and fibrosis and may also play a role in the pathogenesis of severe COVID-19. To further elucidate the role of ECM remodelling and excessive fibrogenesis in severe COVID-19, we examined circulating levels of mediators involved in various aspects of these processes in COVID-19 patients. METHODS: Serial blood samples were obtained from two cohorts of hospitalised COVID-19 patients (n = 414). Circulating levels of ECM remodelling mediators were quantified by enzyme immunoassays in samples collected during hospitalisation and at 3-month follow-up. Samples were related to disease severity (respiratory failure and/or treatment at the intensive care unit), 60-day total mortality and pulmonary pathology after 3-months. We also evaluated the direct effect of inactivated SARS-CoV-2 on the release of the different ECM mediators in relevant cell lines. RESULTS: Several of the measured markers were associated with adverse outcomes, notably osteopontin (OPN), S100 calcium-binding protein A12 and YKL-40 were associated with disease severity and mortality. High levels of ECM mediators during hospitalisation were associated with computed tomography thorax pathology after 3-months. Some markers (i.e. growth differential factor 15, galectin 3 and matrix metalloproteinase 9) were released from various relevant cell lines (i.e. macrophages and lung cell lines) in vitro after exposure to inactivated SARS-CoV-2 suggesting a direct link between these mediators and the causal agent of COVID-19. CONCLUSION: Our findings highlight changes to ECM remodelling and particularly a possible role of OPN, S100A12 and YKL-40 in the pathogenesis of severe COVID-19.

DNA Repair Mechanisms are Activated in Circulating Lymphocytes of Hospitalized Covid-19 Patients.

Purpose: Reactive oxygen species (ROS) are an important part of the inflammatory response during infection but can also promote DNA damage. Due to the sustained inflammation in severe Covid-19, we hypothesized that hospitalized Covid-19 patients would be characterized by increased levels of oxidative DNA damage and dysregulation of the DNA repair machinery. Patients and Methods: Levels of the oxidative DNA lesion 8-oxoG and levels of base excision repair (BER) proteins were measured in peripheral blood mononuclear cells (PBMC) from patients (8-oxoG, n = 22; BER, n = 17) and healthy controls (n = 10) (Cohort 1). Gene expression related to DNA repair was investigated in two independent cohorts of hospitalized Covid-19 patients (Cohort 1; 15 patents and 5 controls, Cohort 2; 15 patients and 6 controls), and by publicly available datasets. Results: Patients and healthy controls showed comparable amounts of oxidative DNA damage as assessed by 8-oxoG while levels of several BER proteins were increased in Covid-19 patients, indicating enhanced DNA repair in acute Covid-19 disease. Furthermore, gene expression analysis demonstrated regulation of genes involved in BER and double strand break repair (DSBR) in PBMC of Covid-19 patients and expression level of several DSBR genes correlated with the degree of respiratory failure. Finally, by re-analyzing publicly available data, we found that the pathway Hallmark DNA repair was significantly more regulated in circulating immune cells during Covid-19 compared to influenza virus infection, bacterial pneumonia or acute respiratory infection due to seasonal coronavirus. Conclusion: Although beneficial by protecting against DNA damage, long-term activation of the DNA repair machinery could also contribute to persistent inflammation, potentially through mechanisms such as the induction of cellular senescence. However, further studies that also include measurements of additional markers of DNA damage are required to determine the role and precise molecular mechanisms for DNA repair in SARS-CoV-2 infection.

Markers of cellular senescence is associated with persistent pulmonary pathology after COVID-19 infection.

BACKGROUND: The lungs are the organ most likely to sustain serious injury from coronavirus disease 2019 (COVID-19). However, the mechanisms for long-term complications are not clear. Patients with severe COVID-19 have shorter telomere lengths and higher levels of cellular senescence, and we hypothesized that circulating levels of the telomere-associated senescence markers chitotriosidase, ß-galactosidase, cathelicidin antimicrobial peptide and stathmin 1 (STMN1) were elevated in hospitalized COVID-19 patients compared to controls and could be associated with pulmonary sequelae following hospitalization. METHODS: Ninety-seven hospitalized patients with COVID-19 who underwent assessment for pulmonary sequelae at three-month follow-up were included in the study. ß-Galactosidase and chitotriosidase were analysed by fluorescence; stathmin 1 and cathelicidin antimicrobial peptide were analysed by enzyme immuno-assay in plasma samples from the acute phase and after three-months. In addition, the classical senescence markers cyclin-dependent kinase inhibitor 1A and 2A were analysed by enzyme immuno-assay in peripheral blood mononuclear cell lysate after three months. RESULTS: We found elevated plasma levels of the senescence markers chitotriosidase and stathmin 1 in patients three months after hospitalization with COVID-19, and these markers in addition to protein levels of cyclin-dependent kinase inhibitor 2A in cell lysate, were associated with pulmonary pathology. The elevated levels of these markers seem to reflect both age-dependent (chitotriosidase) and age-independent (stathmin 1, cyclin-dependent kinase inhibitor 2A) processes. CONCLUSIONS: We suggest that accelerated ageing or senescence could be important for long-term pulmonary complications of COVID-19, and our findings may be relevant for future research exploring the pathophysiology and management of these patients.

High Circulating Levels of the Homeostatic Chemokines CCL19 and CCL21 Predict Mortality and Disease Severity in COVID-19.

BACKGROUND: Immune dysregulation is a major factor in the development of severe coronavirus disease 2019 (COVID-19). The homeostatic chemokines CCL19 and CCL21 have been implicated as mediators of tissue inflammation, but data on their regulation in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is limited. We thus investigated the levels of these chemokines in COVID-19 patients. METHODS: Serial blood samples were obtained from patients hospitalized with COVID-19 (n = 414). Circulating CCL19 and CCL21 levels during hospitalization and 3-month follow-up were analyzed. In vitro assays and analysis of RNAseq data from public repositories were performed to further explore possible regulatory mechanisms. RESULTS: A consistent increase in circulating levels of CCL19 and CCL21 was observed, with high levels correlating with disease severity measures, including respiratory failure, need for intensive care, and 60-day all-cause mortality. High levels of CCL21 at admission were associated with persisting impairment of pulmonary function at the 3-month follow-up. CONCLUSIONS: Our findings highlight CCL19 and CCL21 as markers of immune dysregulation in COVID-19. This may reflect aberrant regulation triggered by tissue inflammation, as observed in other chronic inflammatory and autoimmune conditions. Determination of the source and regulation of these chemokines and their effects on lung tissue is warranted to further clarify their role in COVID-19. CLINICAL TRIALS REGISTRATION: NCT04321616 and NCT04381819.