We report the characteristics of coagulation/fibrinolysis abnormalities in 6 severe coronavirus disease 2019 (COVID-19) patients. One of 6 patients had a platelet count of < 10 × 10⁴/mm³ during the 8-day observation period from ICU admission. Both prothrombin-international normalized ratio and activated partial thromboplastin time remained almost within the normal ranges throughout the 8 days. In contrast, fibrin degradation products and D-dimer levels remained above the upper limits of the normal ranges throughout the 8 days, and levels in 2/6 cases increased markedly from day 7. Therefore, we strongly suspected as if an “enhanced-fibrinolytic type” but not a “suppressed-fibrinolytic type” coagulation/fibrinolysis abnormality, despite COVID-19 being an infectious disease. Disseminated intravascular coagulation (DIC) developed in 4/6 cases, according to the Japanese Association for Acute Medicine criteria DIC diagnostic criteria, and these cases were treated with recombinant human soluble thrombomodulin (rhsTM) for 6–7 days. After the rhsTM treatment the DIC status improved in 3/4 cases.

The measurement of von Willebrand factor (VWF) activity and antigen (Ag) are required to diagnose von Willebrand disease (VWD). In Japan, ristocetin cofactor activity of VWF (VWF:RCo) has been used in a clinical setting. INNOVANCE^® VWF Ac Assay is based on latex immunoagglutination and measures VWF:GPIbM activity, which employ recombinant glycoprotein Ib carrying two gain-of-function mutation. However, it has not been introduced in Japan yet. Here, we evaluated the performance of INNOVANCE^® VWF Ac Assay in CS-5100 autoanalyzer. The results showed that within-run and between-day precision were the CVs of <3% and <2%, respectively. We observed a good dilution linearity and a superior limit of detection compared with VWF:RCo. The VWF:GPIbM assay was not affected by interference substances such as bilirubin, hemolytic hemoglobin and chyle, and also by unfractionated heparin (<10 IU/mL). The correlations of VWF:GPIbM versus VWF:RCo or VWF:Ag were excellent in normal plasma. In plasma from patients with VWD, VWF:GPIbM activity was also correlated with VWF:RCo. Taken together, INNOVANCE^® VWF Ac Assay showed a remarkable performance and it would be expected the future introduction in Japan.

Platelets are released from mature megakaryocytes (MKs) and are used for therapeutic application, especially platelet transfusion. Platelet concentrates used for platelet transfusions are currently supplied by volunteer donors. Due to their short shelf life (4 days in Japan and 5 days in US), however, donor-dependent platelet concentrates are associated with practical problems, such as the limited supply and the risk of infection. Thus, new strategies for manufacturing MKs and subsequently platelets from a donor-independent source are urgently needed. Mesenchymal stem cells (MSCs) are known to be non-hematopoietic multipotent progenitor-cells. We found that MSCs/stromal cells differentiated into MKs and platelets. The clinical needs for platelet transfusions are increasing. Adipose tissue-derived MSCs/stromal cells are an attractive candidate cell source because inducing these cells into MK-lineages requires no gene transfer and only endogenous transcription factors containing p45NF-E2/Maf, an MK-inducing factor and endogenous thrombopoietin, a primary cytokine that drives MK lineages. Thus, we developed a manufacturing system for platelets from donor-independent cell source, human adipose-derived mesenchymal stromal/stem cell line (ASCL). ASCL satisfied the minimal criteria for defining MSC by The International Society for Cellular Therapy. ASCL-derived platelets (ASCL-PLT) were obtained with a peak at Day 12 of culture using MK lineage induction media. We observed that CD42b-positive cells expressed a MSC marker CD90 in relation to cell adhesion. The pattern of in vivo kinetics after being infused into irradiated immunodeficient NSG mice was similar to that of platelet concentrates. ASCL-PLT has characterization observed in other platelet populations and might have additional function as MSC. The present protocol is a simple method that requires no feeder cells, further enhancing the clinical application of our approach.