Production of Megakaryocytes and Platelets from Common Marmoset (Callithrix jacchus) ES Cells by Constitutive Expression of tal1/scl Gene.

Since the successful establishment of human embryonic stem (ES) cell lines in 1998, transplantation of the differentiated ES cells to specific organ has been expected to cure its defective function. For the realistic medicine, the preclinical studies using animal model systems including non-human primates are essential. We have already demonstrated that 1) non-human primates of common marmosets (CM) are suitable for the laboratory animal models for preclinical studies of hematopoietic stem cell therapy and 2) tal1/scl gene transduction using a lentiviral vector is a very useful tool for the efficient hematopoietic cell differentiation from CM ES cells. In this study, we especially focused on the differentiation of CM ES cells to megakaryocytes and platelets in stroma cell-free conditions in order to investigate the feasibility of future new transfusion therapy. Firstly, we established CM ES cell line, which expressed tal1/scl gene constitutively (CM ES-tal1/scl). This ES cell line exhibited undifferentiated morphology and expressed stage-specific embryonic antigen (SSEA)-3 and SSEA-4, while SSEA-1 was not detected. The induction of hematopoietic cells from CM ES-tal1/scl was more efficient than that of original ES cell line. Next, by using this cell line, we planned to produce megakaryocytes and platelets efficiently. During semi-long culture (< 1 month) in the presence of thrombopoietin (10–100 ng/ml), we obtained some proplatelet-like structures, which showed CD41 expression by immunohistostaining, in the adherent cells. Furthermore, 2–4% of CD41 positive platelet-like fraction was observed in the culture supernatant by flow cytometry, although the induction efficiency was low. Now, we examine the efficient culture conditions including additional gene transduction such as gata1, runx1, and NF-E2 genes.