Zheyong Huang

Abstract Background Over 5,488,000 cases of coronavirus disease-19 (COVID-19) have been reported since December 2019. We aim to explore risk factors associated with mortality in COVID-19 patients and assess the use of D-dimer as a biomarker for disease severity and clinical outcome. Methods We retrospectively analyzed the clinical, laboratory, and radiological characteristics of 248 consecutive cases of COVID-19 in Renmin Hospital of Wuhan University, Wuhan, China from January 28 to March 08, 2020. Univariable and multivariable logistic regression methods were used to explore risk factors associated with in-hospital mortality. Correlations of D-dimer upon admission with disease severity and in-hospital mortality were analyzed. Receiver operating characteristic curve was used to determine the optimal cutoff level for D-dimer that discriminated those survivors versus non-survivors during hospitalization. Results Multivariable regression that showed D-dimer > 2.0 mg/L at admission was the only variable associated with increased odds of mortality [OR 10.17 (95% CI 1.10–94.38), P = 0.041]. D-dimer elevation (≥ 0.50 mg/L) was seen in 74.6% (185/248) of the patients. Pulmonary embolism and deep vein thrombosis were ruled out in patients with high probability of thrombosis. D-dimer levels significantly increased with increasing severity of COVID-19 as determined by clinical staging (Kendall’s tau-b = 0.374, P = 0.000) and chest CT staging (Kendall’s tau-b = 0.378, P = 0.000). In-hospital mortality rate was 6.9%. Median D-dimer level in non-survivors ( n = 17) was significantly higher than in survivors ( n = 231) [6.21 (3.79–16.01) mg/L versus 1.02 (0.47–2.66) mg/L, P = 0.000]. D-dimer level of > 2.14 mg/L predicted in-hospital mortality with a sensitivity of 88.2% and specificity of 71.3% (AUC 0.85; 95% CI = 0.77–0.92). Conclusions D-dimer is commonly elevated in patients with COVID-19. D-dimer levels correlate with disease severity and are a reliable prognostic marker for in-hospital mortality in patients admitted for COVID-19.

Rationale: Angiogenesis is a crucial step towards tissue repair and regeneration after ischemia. The role of circulating exosomes in angiogenic signal transduction has not been well elucidated. Thus, this study aims to investigate the effects of coronary serum exosomes from patients with myocardial ischemia on angiogenesis and to elucidate the underlying mechanisms. Methods and Results: The patients were enrolled according to the inclusion and exclusion criteria. Coronary blood was obtained from the angiography catheter. Serum exosomes were purified and characterized by their specific morphology and surface markers. In vitro analysis showed that compared to exosomes from healthy controls (con-Exo), exosomes from patients with myocardial ischemia (isc-Exo) enhanced endothelial cell proliferation, migration and tube formation. In a mouse hind-limb ischemia model, blood perfusion and histological staining demonstrated that isc-Exo significantly promoted blood flow recovery and enhanced neovascularization compared to con-Exo. Further, we revealed that cardiomyocytes, but not cardiac fibroblasts or endothelial cells, were initiated to release exosomes under ischemic stress; cardiomyocytes might be the source of bioactive exosomes in coronary serum. In addition, microarray analysis indicated that miR-939-5p was significantly down-regulated in isc-Exo. By knockdown and overexpression analyses, we found that miR-939-5p regulated angiogenesis by targeting iNOS. miR-939-5p inhibited both iNOS's expression and its activity, attenuated endothelial NO production, and eventually impaired angiogenesis. Conclusions: Exosomes derived from patients with myocardial ischemia promote angiogenesis via the miR-939-iNOS-NO pathway. Our study highlights that coronary serum exosomes serve as an important angiogenic messenger in patients suffering from myocardial ischemia.

Inflammatory modulations focusing on macrophage phenotype are promising candidates to promote better cardiac healing post myocardial ischemia-reperfusion (MI/R) injury. However, the peak of monocyte/macrophage recruitment is later than the time when enhanced permeability and retention effect disappears, which greatly increases the difficulty of reprogramming macrophages through systemic administration. Meanwhile, the inability of nanomaterials to release their contents to specific intracellular locations through reasonable cellular internalization pathways is another obstacle to achieving macrophage reprogramming. Here, inspired by the increase in circulating platelet-monocyte aggregates in patients' post-MI/R and the high efficiency of fusogenic liposomes to deliver contents to the cytoplasm of target cells, a platelet-like fusogenic liposome (PLPs) is constructed. Under the coating of PLPs, mesoporous silica nanospheres with a payload of miR-21, an anti-inflammatory agent, can be specifically delivered to inflammatory monocytes in the blood circulation of MI/R induced mice. Then it directly enters the cytoplasm of monocytes through membrane fusion, thereby realizing the reparative reprogramming of the inflamed macrophages derived from it. In vivo administration of the resulting formula can effectively preserve the cardiac function of mice undergone MI/R. Minimal invasiveness and biological safety make this nano-platform a promising approach of immunotherapy.