Basement membrane product, endostatin, as a link between inflammation, coagulation and vascular permeability in COVID-19 and non-COVID-19 acute respiratory distress syndrome.

Background: Immune cell recruitment, endothelial cell barrier disruption, and platelet activation are hallmarks of lung injuries caused by COVID-19 or other insults which can result in acute respiratory distress syndrome (ARDS). Basement membrane (BM) disruption is commonly observed in ARDS, however, the role of newly generated bioactive BM fragments is mostly unknown. Here, we investigate the role of endostatin, a fragment of the BM protein collagen XVIIIα1, on ARDS associated cellular functions such as neutrophil recruitment, endothelial cell barrier integrity, and platelet aggregation in vitro. Methods: In our study we analyzed endostatin in plasma and post-mortem lung specimens of patients with COVID-19 and non-COVID-19 ARDS. Functionally, we investigated the effect of endostatin on neutrophil activation and migration, platelet aggregation, and endothelial barrier function in vitro. Additionally, we performed correlation analysis for endostatin and other critical plasma parameters. Results: We observed increased plasma levels of endostatin in our COVID-19 and non-COVID-19 ARDS cohort. Immunohistochemical staining of ARDS lung sections depicted BM disruption, alongside immunoreactivity for endostatin in proximity to immune cells, endothelial cells, and fibrinous clots. Functionally, endostatin enhanced the activity of neutrophils, and platelets, and the thrombin-induced microvascular barrier disruption. Finally, we showed a positive correlation of endostatin with soluble disease markers VE-Cadherin, c-reactive protein (CRP), fibrinogen, and interleukin (IL)-6 in our COVID-19 cohort. Conclusion: The cumulative effects of endostatin on propagating neutrophil chemotaxis, platelet aggregation, and endothelial cell barrier disruption may suggest endostatin as a link between those cellular events in ARDS pathology.

Beyond Articular Cartilage: A Systematic Review of the Extracellular Matrix in Other Components of the Osteoarthritic Joint

Background/Aims Traditionally viewed from the perspective of cartilage degeneration, osteoarthritis is increasingly seen as a disease of global joint dysfunction. Connective tissue extracellular matrix (ECM) is a crucial determinant of joint mechanobiology, providing cells with scaffolding, topographical cues, and a reservoir of soluble factors. While ECM dysregulation has been extensively studied in osteoarthritic cartilage, it remains poorly defined in other joint tissues. Here, we systematically review the composition, architecture, and remodelling of non-cartilage soft joint tissue ECM in human osteoarthritis and animal disease models. Methods A systematic search strategy was run through the MEDLINE, EMBASE and Scopus databases on 30 October 2020 and repeated on 1 October 2021. The search criteria included disease nomenclature, relevant tissues, as well as structural ECM components and architectural features. All papers were independently screened by two reviewers on the Covidence platform according to predefined eligibility criteria. Relevant clinical, demographic, and biological data were extracted from included studies, which were assessed for bias using the OHAT Risk of Bias Rating Tool for Human and Animal Studies. Results 148 of 8,156 identified studies met all eligibility criteria. 113 papers evaluated human osteoarthritis;of 35 animal studies, the most frequently used models involved surgical joint destabilisation in small mammals. ECM was best defined in menisci, ligaments, and synovium;fewer papers assessed skeletal muscles, tendons, and fat pads. Compared to the healthy joint, osteoarthritis is associated with qualitative and quantitative alterations in structural ECM components, most notably collagens and proteoglycans. In recent years, whole proteome sequencing has been employed to address these changes systematically. The mechanical properties of ECM change significantly in osteoarthritis in response to post-translational modifications, extensive calcification, and the marked loss of matrix organisation across the joint. Notably, some aspects of ECM remodelling in these tissues appear to precede discernible cartilage dysregulation. Similar ECM dysregulation is also observed in animal models, although intermodel variability in arthritogenic precipitant and the range of reported outcomes make comparisons difficult. Many studies are limited by significant bias, notably in the infrequent reporting of investigator blinding, and in the poor demographic matching of osteoarthritic and control patients. Encouragingly, the quality of methodology reporting and use of age-matched control populations have improved in recent years. Conclusion Current data provide compelling evidence of whole joint ECM changes in osteoarthritis and importantly suggest that these changes occur early in the disease process. How ECM dysfunction affects the behaviour of tissue-resident cells remains less well understood. Our work will support the design of disease-relevant biomaterials used to model osteoarthritis in vitro, helping to address this issue, by more accurately recreating the extracellular environment. Furthermore, the development of imaging modalities sensitive to connective tissue ECM changes warrants investigation from both diagnostic and prognostic perspectives.

Development of a Lymphoid Organ-Chip to Evaluate Covid Vaccine Boosting Strategies

Background: Secondary lymphoid organs provide the adequate microenvironment for the development of antigen (Ag)-specific immune responses. The tight collaboration between CD4+ T cells and B cells in germinal centers is crucial to shape B cell fate and optimize antibody maturation. Dissecting these immune interactions remains challenging in humans, and animal models do not always recapitulate human physiology. To address this issue, we developed an in vitro 3D model of a human lymphoid organ. The model relies on a microfluidic device, enabling primary human cells to self-organize in an extracellular matrix (ECM) under continuous fluid perfusion. We applied this Lymphoid Organ-Chip (LO chip) system to the analysis of B cell recall responses to SARS-CoV-2 antigens. Method(s): We used a two-channel microfluidic Chip S1 from Emulate, where the top channel is perfused with antigen (spike protein or SARS-CoV-2 mRNA vaccine), while the bottom channel contains PBMC (n = 14 independent donors) seeded at high-density in a collagen-based ECM. Immune cell division and cluster formation were monitored by confocal imaging, plasmablast differentiation and spike-specific B cell amplification by flow cytometry, antibody secretion by a cell-based binding assay (S-flow). Result(s): Chip perfusion with the SARS-CoV-2 spike protein for 6 days resulted in the induction CD38hiCD27hi plasmablast maturation compared to an irrelevant BSA protein (P< 0.0001). Using fluorescent spike as a probe, we observed a strong amplification of spike-specific B cell (from 3.7 to 140-fold increase). In line with this rapid memory B cell response, spike-specific antibodies production could be detected as early as day 6 of culture. Spike perfusion also induced CD4+ T cell activation (CD38+ ICOS+), which correlated with the level of B cell maturation. The magnitude of specific B cell amplification in the LO chip was higher than in 2D and 3D static cultures at day 6, showing the added value of 3D perfused culture for the induction of recall responses. Interestingly, the perfusion of mRNA-based SARS-CoV-2 vaccines also led to strong B cell maturation and specific B cell amplification, indicating that mRNA-derived spike could be expressed and efficiently presented in the LO chip. Conclusion(s): We developed a versatile Lymphoid Organ-Chip model suitable for the rapid evaluation of B cell recall responses. The model is responsive to protein and mRNA-encoded antigens, highlighting its potential in the evaluation of SARS-CoV-2 vaccine boosting strategies.

Associations of habitual glucosamine use with SARS-CoV-2 infection and hospital admission and death with COVID-19: Evidence from a large population based cohort study.

The coronavirus disease 2019 (COVID-19) pandemic has led to a fundamental number of morbidity and mortality worldwide. Glucosamine was indicated to help prevent and control RNA virus infection preclinically, while its potential therapeutic effects on COVID-19-related outcomes are largely unknown. To assess the association of habitual glucosamine use with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, hospital admission, and mortality with COVID-19 in a large population based cohort. Participants from UK Biobank were reinvited between June and September 2021 to have SARS-CoV-2 antibody testing. The associations between glucosamine use and the risk of SARS-CoV-2 infection were estimated by logistic regression. Hazard ratios (HRs) and 95% confidence intervals (CIs) for COVID-19-related outcomes were calculated using COX proportional hazards model. Furthermore, we carried out propensity-score matching (PSM) and stratified analyses. At baseline, 42 673 (20.7%) of the 205 704 participants reported as habitual glucosamine users. During median follow-up of 1.67 years, there were 15 299 cases of SARS-CoV-2 infection, 4214 cases of COVID-19 hospital admission, and 1141 cases of COVID-19 mortality. The fully adjusted odds ratio of SARS-CoV-2 infection with glucosamine use was 0.96 (95% CI: 0.92-1.01). The fully adjusted HR were 0.80 (95% CI: 0.74-0.87) for hospital admission, and 0.81 (95% CI: 0.69-0.95) for mortality. The logistic regression and Cox proportional hazard analyses after PSM yielded consistent results. Our study demonstrated that habitual glucosamine use is associated with reduced risks of hospital admission and death with COVID-19, but not the incidence of SARS-CoV-2 infection.

Electrosprayed Mesenchymal Stromal Cell Extracellular Matrix Nanoparticles Accelerate Cellular Wound Healing and Reduce Gram-Negative Bacterial Growth.

Treatments for acute respiratory distress syndrome are still unavailable, and the prevalence of the disease has only increased due to the COVID-19 pandemic. Mechanical ventilation regimens are still utilized to support declining lung function but also contribute to lung damage and increase the risk for bacterial infection. The anti-inflammatory and pro-regenerative abilities of mesenchymal stromal cells (MSCs) have shown to be a promising therapy for ARDS. We propose to utilize the regenerative effects of MSCs and the extracellular matrix (ECM) in a nanoparticle. Our mouse MSC (MMSC) ECM nanoparticles were characterized using size, zeta potential, and mass spectrometry to evaluate their potential as pro-regenerative and antimicrobial treatments. The nanoparticles had an average size of 273.4 nm (±25.6) and possessed a negative zeta potential, allowing them to surpass defenses and reach the distal regions of the lung. It was found that the MMSC ECM nanoparticles are biocompatible with mouse lung epithelial cells and MMSCs, increasing the wound healing rate of human lung fibroblasts while also inhibiting the growth of Pseudomonas aeruginosa, a common lung pathogen. Our MMSC ECM nanoparticles display characteristics of healing injured lungs while preventing bacterial infection, which can increase recovery time.

Cathepsins in the extracellular space: Focusing on non-lysosomal proteolytic functions with clinical implications.

Cathepsins can be found in the extracellular space, cytoplasm, and nucleus. It was initially suspected that the primary physiological function of the cathepsins was to break down intracellular protein, and that they also had a role in pathological processes including inflammation and apoptosis. However, the many actions of cathepsins outside the cell and their complicated biological impacts have garnered much interest. Cathepsins play significant roles in a number of illnesses by regulating parenchymal cell proliferation, cell migration, viral invasion, inflammation, and immunological responses through extracellular matrix remodeling, signaling disruption, leukocyte recruitment, and cell adhesion. In this review, we outline the physiological roles of cathepsins in the extracellular space, the crucial pathological functions performed by cathepsins in illnesses, and the recent breakthroughs in the detection and therapy of specific inhibitors and fluorescent probes in associated dysfunction.

A review of fibroblast-like synoviocytes in the pathogenesis of Rheumatoid arthritis: Their activation and the inhibition of their apoptosis

Rheumatoid Arthritis (RA) is a systemic, autoimmune, inflammatory disease characterized by synovial hyperplasia, inflammatory cell infiltration in the synovial tissues, and progressive destruction of cartilage and bones. This disease often leads to chronic disability. More recently, activation of synovial fibroblasts (SFs) has been linked to innate immune responses and several cellular signalingpathways that ultimately result in the aggressive and invasive stages of RA. SFs are the major sources of pro-inflammatory cytokines in RA synovium. They participate in maintaining the inflammatory state that leads to synovial hyperplasia and angiogenesis in the inflamed synovium. The altered apoptotic response of synovial and inflammatory cells has been connected to these alterations of inflamed synovium. RA synovial fibroblasts (RASFs) have the ability to inhibit several apoptotic proteins that cause their abnormal proliferation. This proliferation leads to synovial hyperplasia. Apoptotic pathway proteins have thus been identified as possible targets for modifying the pathophysiology of RA. This review summarizes current knowledge of SF activation and its roles in the inhibition of apoptosis in the synovium, which is involved in joint damage during the effector phase of RA development.Copyright © 2022 Biomedpress.

Machine Learning analysis of human pulmonary extracellular matrix architecture identifies disease-specific remodeling patterns

Background: Normal organ function is critically dependent on an intact three-dimensional architecture. Structural abnormalities induced by pathological situations instruct cells to behave abnormally and promoting disease progression oftentimes leading to organ failure. Current approaches do not allow for high-resolution (HR) threedimensional (3D) visualisation and analysis of human organ structure. Method(s): Here, we develop a method to perfuse human tissue segments to remove cells and study the 3D structural scaffold, which could be applied to any organ. Our approach enables HR-3D imaging of organ architecture, which we apply to study healthy and diseased human lung, specifically emphysema, usual interstitial pneumonia, pulmonary sarcoidosis, and COVID-19. Result(s): Our imaging reveals major structural abnormalities previously unseen by existing methodologies. Furthermore, we identify disease-specific patterns of structural remodelling using machine learning, including the altered spatial relationship between extracellular matrix (ECM) proteins collagen type IV, elastin and fibrillar collagen present across all diseases. Conclusion(s): Given the importance of organ structure on function, our approach opens the possibility to understand human physiology in a new way, which may assist in future disease diagnosis and explain the detrimental pulmonary effects of the diseases studied here.

Dynamics and Heterogeneity of the Lung Immunopathology in Severe COVID-19

Background: The key impact of SARS-CoV-2 is its ability to cause a life-threatening infection in the lung. Aim(s): Using spatially resolved multiplex imaging the present study decodes the immunopathological complexity of severe COVID-19. Method(s): Autopsy lung tissue from 18 COVID-19 patients was used to map immune and structural cells in acute/exudative, intermediate and advanced diffuse alveolar damage (DAD) through multiplex immunohistochemistry and spatial statistical analyses. Cytokine profiling, viral, bacteria and fungi detection and transcriptome analyses were also performed. Result(s): All cases displayed concomitant patterns of DAD. The spatially resolved multiplex data revealed intricate patchworks of mm -size microenvironments representing distinct immunological niches. In-depth analysis of DAD areas revealed that the temporal/spatial DAD progression is associated with expansion of adaptive immune cells, macrophages, CD8 T cells, fibroblasts, angiogenesis and lymphangiogenesis. Viral load correlated positively with acute DAD and negatively with disease/hospital length. Cytokines correlated mainly with macrophages and CD8 T cells. Pro-coagulation and acute repair markers were enriched in acute DAD whereas intermediate/advanced DAD had a molecular profile of elevated humoral and innate immune responses and extracellular matrix production. Conclusion(s): Our unraveling of the spatio-temporal immunopathology in COVID-19 cases exposes the heterogeneous dynamics of acute viral infection and subsequent responses that occur side-by-side in the lungs. This complex disease feature has important implications for disease management and development of novel immunemodulatory treatments.

Differentially expressed genes in Diffuse Alveolar Damage (DAD) patterns of COVID-19

Severe COVID-19 induces DAD, a condition with temporal-spatial heterogeneity. We determined the differentially expressed genes (DEGs) in the histological patterns of DAD. Twelve fatal COVID-19 cases were classified in acute DAD (n=5) and intermediate/advanced (IA) DAD (n=7). Autopsy lung RNA was extracted from COVID-19 and 4 control cases. RNA sequencing was performed on the Illumina NovaSeq 6000. Enrichment analysis was performed with clusterProfiler using Genome-wide annotation for Human R package. GO terms and KEGG pathways were considered enriched if adjusted p<=0.05. Principal component analysis showed that IA-DAD samples were grouped, while acute DAD samples were scattered. The differential expression analysis between these two groups and the control cases revealed: 261 DEGs in the acute DAD (143 Up- and 53 Down-regulated), 244 DEGs in the IA- DAD tissues (67 Up- and 116 Down-regulated), and 61 DEGs were shared between them (45 Up- and 16 Downregulated). Patients with acute DAD had up-regulated genes related to oxidative phosphorylation, blood coagulation, megakaryocytes differentiation/regulation, and platelet degranulation/activation. Patients with IA-DAD had DEGs related to immunoglobulins and extracellular matrix. The shared up-regulated DEGs between both patterns are involved in innate and adaptive immune responses. We selected 3 DEGs in each DAD pattern for validation by realtime PCR. There were no differences in acute DAD DEGs, but DEGs overexpressed in intermediate DAD (COL3A1, IGLV3-19, IGHV1-58) were significantly higher. Genes related to thrombotic events occur at the acute stage of DAD, whereas immunoglobulin production and remodeling occur at later stages of DAD.

Serological markers of tissue remodeling are elevated in patients with COVID-19 who develop interstitial lung disease

Background: Coronavirus disease-19 (COVID-19) is an infectious disease that can result in serious respiratory illness. It is associated with extensive systemic inflammation and changes to the lung extracellular matrix (ECM), which may result in diffuse alveolar damage and pulmonary fibrosis. In this study, the aim was to investigate whether ECM remodeling, wound healing, and neutrophil activity is altered in patients with COVID-19, with or without interstitial lung disease (ILD). Method(s): Serum was collected from 72 patients with COVID-19 infection 3 months after diagnosis, 10 of whom developed ILD, and from 16 healthy controls. A panel of neo-epitope specific ELISAs reflecting type III collagen crosslinking (PC3X), type III and VI collagen formation (PRO-C3 and PRO-C6), type I, III, and VI collagen degradation (C1M, C3M, and C6M), fibrin crosslinking (X-FIB), fibrin clot formation (PRO-FIB), elastin degradation (EL-NE and ELP-3), and calprotectin degradation (CPa9-HNE) were assessed in serum of patients. Result(s): Mean serum neo-epitopes PC3X (p<0.0001), PRO-C3 (p=0.0024), C3M (p=0.0085), PRO-FIB (p<0.0001), ELP-3 (p<0.0001), and CPa9-HNE (p<0.0001) were significantly elevated in patients with COVID-19 compared to healthy controls. Additionally, PC3X (p=0.023) and PRO-C3 (p=0.0317) were significantly elevated in COVID-19 patients who developed ILD when compared to those who did not. Conclusion(s): Non-invasive serological biomarkers reflecting tissue remodeling were significantly elevated in patients infected with COVID-19. Additionally, type III collagen crosslinking and formation may differentiate patients who develop ILD consequent to COVID-19 infection.

Establishment of an in vitro assay to detect antibody-mediated procoagulant platelet formation on a single cell level in real time

Introduction Procoagulant platelets (PLTs), a subpopulation of PLTs that is characterized by increased externalization of phosphatidylserine (PS), are increasingly identified to promote a prothrombotic environment in different diseases. Recently we observed that procoagulant PLT formation can be induced via engagement of immune receptor Fc-gamma-RIIA by COVID-19, VITT and HIT patient immunoglobulin subclass G (IgG) antibodies (Abs). Here, Fc-gamma- RIIA engagement by patient Abs resulted in significant formation of procoagulant PLTs and loss of mitochondrial potential that was associated with high thrombin formation as well as increased thrombus formation. In the cur- rent study, we aim to establish a PLT adhesion assay that allows investigation of PLT mitochondria during procoagulant PLT formation. Method PLTs were spread on human serum albumin, fibrinogen or collagen precoated glass slides. Adhesion and subsequent shape change of PLTs as well as procoagulant PLT formation were investigated in real time using immune fluorescence microscopy. For the detection of PLT shape change, mitochondrial dynamics and PS externalization, PLTs were double stained with MitoTracker green, a mitochondrial dye that binds to free thiol groups of cysteine residues in the mitochondrial membrane, and Annexin-V, respectively. For the visualization of mitochondrial release from PLTs intracellular compartment, a monoclonal Ab that binds to a subunit of the translocase of the outer membrane (TOM) complex on the mitochondrial membrane, namely TOM22, was used. Results During the observation period, a subgroup of PLTs that was spread on collagen became procoagulant as determined by an increased binding of Annexin- V on the PLT surface. Contrary, these changes were nearly absent in PLTs that adhered to fibrinogen (percentage [ %] of Annexin-V positive cells: 19.80 +/- 3.42 % vs. 1.92 +/- 0.62 %, p value 0.0357). Interestingly, procoagulant PLT formation was associated with a significant loss of MitoTracker green signal in PLTs while it remained constant in non-procoagulant PLTs attached on both extracellular matrix coatings. Loss of MitoTracker green signal was associated with translocation of mitochondrial proteins from intracellular to extracellular, as a higher count of TOM22 Ab-positive labelled structures, most likely extracellular mitochondria were detected on collagen but not on fibrinogen coated glass slides. Conclusion Our findings indicate, that the formation of procoagulant PLTs is associated with dramatic changes of the mitochondrial integrity in PLTs. Further attempts, that investigate the potential pathophysiological role of PLT mitochondrial release in Ab-mediated prothrombotic disorders may contribute to a further understanding of the role of PLT mitochondria in these complex diseases.

Chemokines and chemokine receptors during COVID-19 infection.

Chemokines are crucial inflammatory mediators needed during an immune response to clear pathogens. However, their excessive release is the main cause of hyperinflammation. In the recent COVID-19 outbreak, chemokines may be the direct cause of acute respiratory disease syndrome, a major complication leading to death in about 40% of severe cases. Several clinical investigations revealed that chemokines are directly involved in the different stages of SARS-CoV-2 infection. Here, we review the role of chemokines and their receptors in COVID-19 pathogenesis to better understand the disease immunopathology which may aid in developing possible therapeutic targets for the infection.

Multiple Fibroblast Subtypes Contribute to Matrix Deposition in Pulmonary Fibrosis.

Progressive pulmonary fibrosis results from a dysfunctional tissue repair response and is characterized by fibroblast proliferation, activation, and invasion and extracellular matrix accumulation. Lung fibroblast heterogeneity is well recognized. With single-cell RNA sequencing, fibroblast subtypes have been reported by recent studies. However, the roles of fibroblast subtypes in effector functions in lung fibrosis are not well understood. In this study, we incorporated the recently published single-cell RNA-sequencing datasets on murine lung samples of fibrosis models and human lung samples of fibrotic diseases and analyzed fibroblast gene signatures. We identified and confirmed the novel fibroblast subtypes we reported recently across all samples of both mouse models and human lung fibrotic diseases, including idiopathic pulmonary fibrosis, systemic sclerosis-associated interstitial lung disease, and coronavirus disease (COVID-19). Furthermore, we identified specific cell surface proteins for each fibroblast subtype through differential gene expression analysis, which enabled us to isolate primary cells representing distinct fibroblast subtypes by flow cytometry sorting. We compared matrix production, including fibronectin, collagen, and hyaluronan, after profibrotic factor stimulation and assessed the invasive capacity of each fibroblast subtype. Our results suggest that in addition to myofibroblasts, lipofibroblasts and Ebf1+ (Ebf transcription factor 1+) fibroblasts are two important fibroblast subtypes that contribute to matrix deposition and also have enhanced invasive, proliferative, and contraction phenotypes. The histological locations of fibroblast subtypes are identified in healthy and fibrotic lungs by these cell surface proteins. This study provides new insights to inform approaches to targeting lung fibroblast subtypes to promote the development of therapeutics for lung fibrosis.

Receptor-binding domain of SARS-CoV-2 is a functional αv-integrin agonist.

Among the novel mutations distinguishing SARS-CoV-2 from similar coronaviruses is a K403R substitution in the receptor-binding domain (RBD) of the viral spike (S) protein within its S1 region. This amino acid substitution occurs near the angiotensin-converting enzyme 2-binding interface and gives rise to a canonical RGD adhesion motif that is often found in native extracellular matrix proteins, including fibronectin. Here, the ability of recombinant S1-RBD to bind to cell surface integrins and trigger downstream signaling pathways was assessed and compared with RGD-containing, integrin-binding fragments of fibronectin. We determined that S1-RBD supported adhesion of fibronectin-null mouse embryonic fibroblasts as well as primary human small airway epithelial cells, while RBD-coated microparticles attached to epithelial monolayers in a cation-dependent manner. Cell adhesion to S1-RBD was RGD dependent and inhibited by blocking antibodies against αv and ß3 but not α5 or ß1 integrins. Similarly, we observed direct binding of S1-RBD to recombinant human αvß3 and αvß6 integrins, but not α5ß1 integrins, using surface plasmon resonance. S1-RBD adhesion initiated cell spreading, focal adhesion formation, and actin stress fiber organization to a similar extent as fibronectin. Moreover, S1-RBD stimulated tyrosine phosphorylation of the adhesion mediators FAK, Src, and paxillin; triggered Akt activation; and supported cell proliferation. Thus, the RGD sequence of S1-RBD can function as an αv-selective integrin agonist. This study provides evidence that cell surface αv-containing integrins can respond functionally to spike protein and raises the possibility that S1-mediated dysregulation of extracellular matrix dynamics may contribute to the pathogenesis and/or post-acute sequelae of SARS-CoV-2 infection.

Role of the extracellular matrix in COVID-19.

An outbreak of coronavirus disease 2019 (COVID-19) has spread globally, with over 500 million cases and 6 million deaths to date. COVID-19 is associated with a systemic inflammatory response and abnormalities of the extracellular matrix (ECM), which is also involved in inflammatory storms. Upon viral infection, ECM proteins are involved in the recruitment of inflammatory cells and interference with target organ metabolism, including in the lungs. Additionally, serum biomarkers of ECM turnover are associated with the severity of COVID-19 and may serve as potential targets. Consequently, understanding the expression and function of ECM, particularly of the lung, during severe acute respiratory syndrome of the coronavirus 2 infection would provide valuable insights into the mechanisms of COVID-19 progression. In this review, we summarize the current findings on ECM, such as hyaluronic acid, matrix metalloproteinases, and collagen, which are linked to the severity and inflammation of COVID-19. Some drugs targeting the extracellular surface have been effective. In the future, these ECM findings could provide novel perspectives on the pathogenesis and treatment of COVID-19.

Proteomic profiling of end-stage COVID-19 lung biopsies.

The outbreak of a novel coronavirus (SARS-CoV-2) in 2019 led to a worldwide pandemic, which remains an integral part of our lives to this day. Coronavirus disease (COVID-19) is a flu like condition, often accompanied by high fever and respiratory distress. In some cases, conjointly with other co-morbidities, COVID-19 can become severe, leading to lung arrest and even death. Although well-known from a clinical standpoint, the mechanistic understanding of lethal COVID-19 is still rudimentary. Studying the pathology and changes on a molecular level associated with the resulting COVID-19 disease is impeded by the highly infectious nature of the virus and the concomitant sampling challenges. We were able to procure COVID-19 post-mortem lung tissue specimens by our collaboration with the BSL-3 laboratory of the Biobanking and BioMolecular resources Research Infrastructure Austria which we subjected to state-of-the-art quantitative proteomic analysis to better understand the pulmonary manifestations of lethal COVID-19. Lung tissue samples from age-matched non-COVID-19 patients who died within the same period were used as controls. Samples were subjected to parallel accumulation-serial fragmentation combined with data-independent acquisition (diaPASEF) on a timsTOF Pro and obtained raw data was processed using DIA-NN software. Here we report that terminal COVID-19 patients display an increase in inflammation, acute immune response and blood clot formation (with concomitant triggering of fibrinolysis). Furthermore, we describe that COVID-19 diseased lungs undergo severe extracellular matrix restructuring, which was corroborated on the histopathological level. However, although undergoing an injury, diseased lungs seem to have impaired proliferative and tissue repair signalling, with several key kinase-mediated signalling pathways being less active. This might provide a mechanistic link to post-acute sequelae of COVID-19 (PASC; "Long COVID"). Overall, we emphasize the importance of histopathological patient stratification when interpreting molecular COVID-19 data.

Characterization of the Proteomic Changes via SARS-CoV-2 Infection or Vaccination in the COVID-19 Community Research Partnership (CCRP)

Background. There remain important gaps in knowledge concerning the effects of SARS-CoV-2 infection or vaccination on the human blood proteome. Methods. The CCRP is a longitudinal surveillance study with information on SARS-CoV-2 infections, vaccinations and associated humoral immune responses in over 37,000 individuals. We selected a sample of blood spots cards (n=510) from serum antibody studies obtained between October 2020 and April 2021 for mass spectrometry proteomics analysis covering 540 unique plasma proteins. We analyzed the quantified protein differences based on dried blood samples obtained before and after infection or vaccination among previously non-infected individuals (immune naive) after adjustment for batch effects, age, sex, or prior diagnosis of cancer, cardiovascular or autoimmune disease, or diabetes. The majority of infected individuals were minimally symptomatic. Differentially expressed proteins were considered significant with an FDR adjusted p-value of < 0.05 and log2 fold change (L2FC) >0.2. Results. We found 11 and 12 proteins differentially expressed proteins in the naive/infected and naive/vaccinated people respectively, of which 10 were shared. Hepatocyte growth factor receptor (HGF) was upregulated (L2FC 0.24;p < 0.001) only in those who were infected while fibrillarin (L2FC -0.24;p< 0.001) and lambdacrystallin homolog (L2FC -0.29, p < 0.001) were downregulated only in the vaccinated samples (Fig 1). The remaining DE protein were associated with a wide array of functions including metabolic, cytostructural, extracellular matrix and DNA regulatory processes. Conclusion. We found changes in the proteome both from infection and vaccination. HGF, elevated in the infected, has been associated with endothelial inflammation, upregulation of pro-inflammatory cytokines to reduce lung fibrosis and is known to promote tissue repair. Fibrillarin, downregulated in the vaccinated, has been associated with higher rates of bacterial and viral clearance, inflammation reduction, and increased cell survival. These findings suggest detectable complex inflammation from mild to moderate infections. Further investigation is required to understand the mechanism of action and clinical implication of these findings.

Glucocorticoid Effects on Proteoglycans and Glycosaminoglycans.

Glucocorticoids are steroid hormones that play diverse roles in numerous normal and pathological processes. They are actively used to treat a wide variety of diseases, including neurodegenerative and inflammatory diseases, cancers, and COVID-19, among others. However, the long-term use of glucocorticoids is associated with numerous side effects. Molecular mechanisms of these negative side effects are not completely understood. Recently, arguments have been made that one such mechanisms may be related to the influence of glucocorticoids on O-glycosylated components of the cell surface and extracellular matrix, in particular on proteoglycans and glycosaminoglycans. The potential toxic effects of glucocorticoids on these glycosylated macromolecules are particularly meaningful for brain physiology because proteoglycans/glycosaminoglycans are the main extracellular components of brain tissue. Here, we aim to review the known effects of glucocorticoids on proteoglycan expression and glycosaminoglycan content in different tissues, with a specific focus on the brain.