2020 Volume 31 Issue 4 Pages 432-438
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.
