COVID-19 and stroke: A review

COVID-19 patients have presented with a wide range of neurological disorders, among which stroke is the most devastating. We have reviewed current studies, case series, and case reports with a focus on COVID-19 patients complicated with stroke, and presented the current understanding of stroke in this patient population. As evidenced by increased D-dimer, fibrinogen, factor VIII and von Willebrand factor, SARS-CoV-2 infection induces coagulopathy, disrupts endothelial function, and promotes hypercoagulative state. Collectively, it predisposes patients to cerebrovascular events. Additionally, due to the unprecedented strain on the healthcare system, stroke care has been inevitably compromised. The underlying mechanism between COVID-19 and stroke warrants further study, so does the development of an effective therapeutic or preventive intervention.

Blood Group Antigen Expression in Isolated Human Liver Cells in Preparation for Implementing Clinical ABO-Incompatible Hepatocyte Transplantation

BACKGROUND

ABO blood group antigens in the liver are expressed mainly on endothelial cells or biliary epithelial cells but not on hepatocytes. This suggests that ABO-incompatible hepatocyte transplantation (ABOi-HTx) is theoretically feasible. However, the effects of stress on ABO blood group antigen expression caused by isolation and intraportal infusion require thorough investigation before ABOi-HTx can be implemented in clinical settings.

METHODS

Human hepatocytes were isolated from liver tissue obtained from liver resection or deceased donor livers. The expression of blood group antigens on cryopreserved human liver tissues and isolated hepatocyte smear specimens were examined by immunofluorescent staining. The effect of proinflammatory cytokines on blood group antigen expression of hepatocytes was evaluated by flow cytometry. Instant blood-mediated inflammatory reaction after hepatocyte incubation with ABO-incompatible whole blood was examined using the tubing loop model.

RESULTS

Blood group antigens were mainly expressed on vessels in the portal area. In hepatocyte smear specimens, isolated hepatocytes did not express blood group antigens. In contrast, a subset of cells in the smear specimens of nonparenchymal liver cells stained positive. In the flow cytometry analysis, isolated hepatocytes were negative for blood group antigens, even after 4-h incubation with cytokines. Platelet counts and complement activation were not significantly different in ABO-identical versus ABO-incompatible settings in the tubing loop model.

CONCLUSION

Our study showed that blood group antigens were not expressed on hepatocytes, even after isolation procedures or subsequent incubation with cytokines. This finding is an important step toward removing the restriction of ABO matching in hepatocyte transplantation. Our results suggest that ABOi-HTx is a feasible therapeutic option, especially in patients who require urgent treatment with freshly isolated hepatocytes, such as those with acute liver failure.