Предшественники тромбоцитов- уязвимы
Исследователи из Алабамы в своей работе показали, чтом мегакариоциты заражаются коронавирусом при ковиде.
При коронавирусной инфекции образцы крови и аутопсии показали, что мегакариоциты мобилизируются в кровеносное русло и органы, вероятно, чтобы компенсировать потери тромбоцитов (которые аггрегируются в тромбы при ковиде). Так же, мегакариоциты продуцируют калпротектин (антимикробный белок, преимущесвтенно, выделяемый нейтрофилами и моноцитами), и его повышенные количества в крови, как и наличие мегакариоцитов, могут служить маркером тяжести болезни.
Белок шипика обнруживался и на поверхности мембран и в районе аппарата Гольджи мегакариоцитов, подвтерждая, что клетки заражены вирусом. Вирусная РНК была обнаружена внутри мегакариоцитов. Авторы считают, что это поясняет, почему в тромбоцитах тоже может находиться вирусная РНК- она попадает туда из "материнской" клетки, зараженной вирусом.
Это певрый случай, считают авторы, что "респираторный" вирус оказался способным заражать мегакааиоциты.
We demonstrate a positive correlation between infected megakaryocytes expressing the protein calprotectin (also called S100A8/A9), a known marker of COVID-19 severity. Additionally, we show that infected, calprotectin expressing megakaryocytes are correlated with COVID-19 severity and are a prognostic indicator of 30-day clinical outcomes including respiratory failure, thrombotic events, acute kidney injury (AKI), ICU admission, and mechanical ventilation. These findings represent a novel SARS-CoV-2 infection target with significant clinical implications as a biomarker for clinical outcomes associated with severe COVID-19.
Circulating megakaryocytes from COVID-19positive patients were then stained for calprotectin and SARS-CoV-2 spike protein, a canonical marker of COVID-19 infec-tion. We identified three distinct circulating megakaryocyte populations in COVID-19 infected patients (Figure 1E): doublenegative circulating megakaryocytes (calprotectin- spike-, Figure 1D, lower-left quadrant), calprotectin positive circulat-ing megakaryocytes (calprotectin+ spike-, Figure 1D, upper-left quadrant), and double positive circulating megakaryocytes(calprotectin+ spike+, Figure 1D, upper-right quadrant)7. Using the PrimeFlow assay, we confirmed the simultaneouspresence of calprotectin mRNA and protein in the calprotectin+ spike+ circulating megakaryocytes (Figure 1F), providingevidence that megakaryocytes are actively producing antimicrobial proteins in the context of SARS-CoV-2 infection. Wethen hypothesized that SARS-CoV-2 could be replicating in megakaryocytes and potentially inducing aberrant expressionof calprotectin. Flow cytometry imaging of circulating megakaryocyte populations revealed cells with large nuclei charac-teristic of megakaryocytes that displayed CD61, CD41, calprotectin, and spike protein (Figure 1G12. Spike protein stainingin the calprotectin+ circulating megakaryocytes exhibited a punctate perinuclear pattern (Figure 1G, red), consistent withSARS-CoV-2 replication in the Golgi complex13. In infected circulating megakaryocytes, we observed the formation of pos-sible proplatelets that contained spike protein (Figure 1G, inset white arrow), raising the intriguing possibility that infectedmegakaryocytes may be a source of SARS-CoV-2 containing platelets. While further studies are required to show passageof virus from megakaryocyte to platelet, our results provide a plausible explanation for the recent paradoxical observationof human platelets containing SARS-CoV-2 RNA without expressing angiotensin-converting enzyme 2 (ACE2) required forviral entry To determine the susceptibility of megakaryocytes to SARS-CoV-2 infection, we inves-tigated three proteins involved in SARS-CoV-2 infection of host cells: 1) ACE2, 2) transmembrane protease serine 2 (TM-PRSS2), 3) FURIN protease13. We found that ACE2 and TMPRSS2 had increased expression in the calprotectin+ spike+megakaryocytes (Figure 1I). FURIN was significantly upregulated in both the calprotectin+ spike+ and calprotectin- spike+circulating megakaryocytes (Figure 1I). In addition to viral receptors, we also stained for two markers of megakaryocyteactivation (P-selectin and activated GPIIb/IIIa), both of which had increased expression in the calprotectin+ spike+ cir-culating megakaryocyte population (Figure 1I). Taken in sum, these findings represent the strongest evidence to date formegakaryocytes as a novel SARS-CoV-2 infection target. We observed DNA+ (Hoescht stain), CD61+, calprotectin+, spike+ megakary-ocytes in COVID-19 ARDS lung tissue (Figure 2A), confirming the presence of infected calprotectin+ megakaryocytes in theparenchyma of diseased organs in addition to peripheral circulation. We then investigated the relationship between calpro-tectin+ spike+ circulating megakaryocyte proportion, laboratory measurements, and adverse clinical outcomes. Lymphopenia and neutrophilia arewidely recognized CBC measurements indicative of severe COVID-19 infection, suggesting that calprotectin+ spike+ circu-lating megakaryocyte may be an additional biomarker of COVID-19 severity16. In agreement, we observed a significantlygreater calprotectin+ spike+ megakaryocyte proportion in patients with higher WHO COVID-19 severity scores comparedto those on room air at the time of sample collection (Figure 2C, red) and at each patient’s worst severity score recordedduring their entire inpatient stay. Using multiple methods, our study establishes megakaryocytes as a novel target of SARS-CoV-2 infection, expressingACE2, TMPRSS2, and FURIN to facilitate viral entry. Further, these infected megakaryocytes contain uniquely high levels ofcalprotectin (S100A8/A9), an antimicrobial protein characteristically expressed by neutrophils and classical monocytes, andfound to be elevated in myeloid populations in severe COVID-1910. Our work not only highlights infected megakaryocytesin circulation but also shows them in target organs, such as the lung. The identification of this cell population in criticalillness provides the strong possibility that they may serve as biomarkers in other ICU-related disorders. To our knowledge, this represents the first biomarker inCOVID-19 subjects with associations across multiple metrics of disease severity. Moreover, this work constitutes the firstevidence of megakaryocyte infection by any respiratory virus and suggest that megakaryocytes may be susceptible to otherviral pathogens in the coronavirus family.
При коронавирусной инфекции образцы крови и аутопсии показали, что мегакариоциты мобилизируются в кровеносное русло и органы, вероятно, чтобы компенсировать потери тромбоцитов (которые аггрегируются в тромбы при ковиде). Так же, мегакариоциты продуцируют калпротектин (антимикробный белок, преимущесвтенно, выделяемый нейтрофилами и моноцитами), и его повышенные количества в крови, как и наличие мегакариоцитов, могут служить маркером тяжести болезни.
Белок шипика обнруживался и на поверхности мембран и в районе аппарата Гольджи мегакариоцитов, подвтерждая, что клетки заражены вирусом. Вирусная РНК была обнаружена внутри мегакариоцитов. Авторы считают, что это поясняет, почему в тромбоцитах тоже может находиться вирусная РНК- она попадает туда из "материнской" клетки, зараженной вирусом.
Это певрый случай, считают авторы, что "респираторный" вирус оказался способным заражать мегакааиоциты.
We demonstrate a positive correlation between infected megakaryocytes expressing the protein calprotectin (also called S100A8/A9), a known marker of COVID-19 severity. Additionally, we show that infected, calprotectin expressing megakaryocytes are correlated with COVID-19 severity and are a prognostic indicator of 30-day clinical outcomes including respiratory failure, thrombotic events, acute kidney injury (AKI), ICU admission, and mechanical ventilation. These findings represent a novel SARS-CoV-2 infection target with significant clinical implications as a biomarker for clinical outcomes associated with severe COVID-19.
Circulating megakaryocytes from COVID-19positive patients were then stained for calprotectin and SARS-CoV-2 spike protein, a canonical marker of COVID-19 infec-tion. We identified three distinct circulating megakaryocyte populations in COVID-19 infected patients (Figure 1E): doublenegative circulating megakaryocytes (calprotectin- spike-, Figure 1D, lower-left quadrant), calprotectin positive circulat-ing megakaryocytes (calprotectin+ spike-, Figure 1D, upper-left quadrant), and double positive circulating megakaryocytes(calprotectin+ spike+, Figure 1D, upper-right quadrant)7. Using the PrimeFlow assay, we confirmed the simultaneouspresence of calprotectin mRNA and protein in the calprotectin+ spike+ circulating megakaryocytes (Figure 1F), providingevidence that megakaryocytes are actively producing antimicrobial proteins in the context of SARS-CoV-2 infection. Wethen hypothesized that SARS-CoV-2 could be replicating in megakaryocytes and potentially inducing aberrant expressionof calprotectin. Flow cytometry imaging of circulating megakaryocyte populations revealed cells with large nuclei charac-teristic of megakaryocytes that displayed CD61, CD41, calprotectin, and spike protein (Figure 1G12. Spike protein stainingin the calprotectin+ circulating megakaryocytes exhibited a punctate perinuclear pattern (Figure 1G, red), consistent withSARS-CoV-2 replication in the Golgi complex13. In infected circulating megakaryocytes, we observed the formation of pos-sible proplatelets that contained spike protein (Figure 1G, inset white arrow), raising the intriguing possibility that infectedmegakaryocytes may be a source of SARS-CoV-2 containing platelets. While further studies are required to show passageof virus from megakaryocyte to platelet, our results provide a plausible explanation for the recent paradoxical observationof human platelets containing SARS-CoV-2 RNA without expressing angiotensin-converting enzyme 2 (ACE2) required forviral entry To determine the susceptibility of megakaryocytes to SARS-CoV-2 infection, we inves-tigated three proteins involved in SARS-CoV-2 infection of host cells: 1) ACE2, 2) transmembrane protease serine 2 (TM-PRSS2), 3) FURIN protease13. We found that ACE2 and TMPRSS2 had increased expression in the calprotectin+ spike+megakaryocytes (Figure 1I). FURIN was significantly upregulated in both the calprotectin+ spike+ and calprotectin- spike+circulating megakaryocytes (Figure 1I). In addition to viral receptors, we also stained for two markers of megakaryocyteactivation (P-selectin and activated GPIIb/IIIa), both of which had increased expression in the calprotectin+ spike+ cir-culating megakaryocyte population (Figure 1I). Taken in sum, these findings represent the strongest evidence to date formegakaryocytes as a novel SARS-CoV-2 infection target. We observed DNA+ (Hoescht stain), CD61+, calprotectin+, spike+ megakary-ocytes in COVID-19 ARDS lung tissue (Figure 2A), confirming the presence of infected calprotectin+ megakaryocytes in theparenchyma of diseased organs in addition to peripheral circulation. We then investigated the relationship between calpro-tectin+ spike+ circulating megakaryocyte proportion, laboratory measurements, and adverse clinical outcomes. Lymphopenia and neutrophilia arewidely recognized CBC measurements indicative of severe COVID-19 infection, suggesting that calprotectin+ spike+ circu-lating megakaryocyte may be an additional biomarker of COVID-19 severity16. In agreement, we observed a significantlygreater calprotectin+ spike+ megakaryocyte proportion in patients with higher WHO COVID-19 severity scores comparedto those on room air at the time of sample collection (Figure 2C, red) and at each patient’s worst severity score recordedduring their entire inpatient stay. Using multiple methods, our study establishes megakaryocytes as a novel target of SARS-CoV-2 infection, expressingACE2, TMPRSS2, and FURIN to facilitate viral entry. Further, these infected megakaryocytes contain uniquely high levels ofcalprotectin (S100A8/A9), an antimicrobial protein characteristically expressed by neutrophils and classical monocytes, andfound to be elevated in myeloid populations in severe COVID-1910. Our work not only highlights infected megakaryocytesin circulation but also shows them in target organs, such as the lung. The identification of this cell population in criticalillness provides the strong possibility that they may serve as biomarkers in other ICU-related disorders. To our knowledge, this represents the first biomarker inCOVID-19 subjects with associations across multiple metrics of disease severity. Moreover, this work constitutes the firstevidence of megakaryocyte infection by any respiratory virus and suggest that megakaryocytes may be susceptible to otherviral pathogens in the coronavirus family.