Term Platelet Research Articles

Upregulation of cAMP prevents antibody-mediated thrombus formation in COVID-19

AbstractThromboembolic events are frequently reported in patients infected with the SARS-CoV-2 virus. The exact mechanisms of COVID-19-associated hypercoagulopathy, however, remain elusive. Recently, we observed that platelets (PLTs) from patients with severe COVID-19 infection express high levels of procoagulant markers, which were found to be associated with increased risk for thrombosis. In the current study, we investigated the time course as well as the mechanisms leading to procoagulant PLTs in COVID-19. Our study demonstrates the presence of PLT-reactive IgG antibodies that induce marked changes in PLTs in terms of increased inner-mitochondrial transmembrane potential (Δψ) depolarization, phosphatidylserine (PS) externalization, and P-selectin expression. The IgG-induced procoagulant PLTs and increased thrombus formation were mediated by ligation of PLT Fc-γ RIIA (FcγRIIA). In addition, contents of calcium and cyclic-adenosine-monophosphate (cAMP) in PLTs were identified to play a central role in antibody-induced procoagulant PLT formation. Most importantly, antibody-induced procoagulant events, as well as increased thrombus formation in severe COVID-19, were inhibited by Iloprost, a clinically approved therapeutic agent that increases the intracellular cAMP levels in PLTs. Our data indicate that upregulation of cAMP could be a potential therapeutic target to prevent antibody-mediated coagulopathy in COVID-19 disease.

Bone marrow stromal cells transduced with a thrombopoietin, interleukin-6, and interleukin-11 syncretic gene induce cord mononuclear cells to generate platelets in vitro.

The induction of hematopoietic stem cells to produce mass numbers of platelets (PLTs) in vitro is an effective method to address a lack of PLTs and PLT transfusion resistance in the clinic. However, the design of a low-cost and sustainable culture system is currently problematic. Here, the thrombopoietin, interleukin (IL)-6, and IL-11 genes, three regulatory factors important for thrombopoiesis, were used to construct self-splicing fusion genes linked by foot and mouth disease (F2A) and Theiler's murine encephalitis (T2A) viruses. Bone marrow stromal cells (BMSCs) transduced with the fusion gene acted as nourishing cells and induced cord blood mononuclear cells (MNCs) to generate PLTs in vitro. We counted these cells; determined the percentage of cells expressing specific cell surface markers (CD41); and measured their ability to aggregate via flow cytometry, immunohistochemical staining, and aggregation remote analyzer. BMSCs transduced with the fusion gene successfully induced cord blood MNCs to generate PLT-sized fragments in the absence of exogenous cytokines. The output was higher than that of the control groups, and the PLT-sized fragments were similar to endogenous PLTs in terms of shape, CD41 expression, and aggregation function. These results suggest that our method could be used to develop a low-cost sustainable cultivation system that generates PLTs in vitro by enhancing the autocrine production of related cytokines through the nourishment provided by cells transduced with a syncretic gene.