CD226 Is Expressed On The Megakaryocytic Lineage From Hematopoietic Stem Cells/progenitor Cells And Neutral Cell-lineage Involved In Polyploidization Megakaryocytes

[Objectives] In this study, we examined the expression of CD226 on megakaryocytic, granulocytic and erythroid lineages from hematopoietic stem cells/progenitor cells in adult and fetus and its potential role in megakaryocytic maturation. We also investgated the potential of fetal liver derived-CD34~+cells induced by TPO to proliferate and differentiate further into neural stem cells and neural cells and analyzed and expression of CD226 on theses cells during transdefferetiation from hematopoietc cells to neural cells.[Methods] CD34~+ cells isolated from adult and fetus were induced to differentiate toward the megakaryocytic lineage by thrombopoietin (TPO) and the granulocytic lineage by granulocyte colony-stimulating factor(G-CSF), respectively. Mononuclear cells from fetal liver and CD34~+ cells from adultwere induced to differentiate toward erythroid-lineage by erythropoietin (EPO). FL derived-CD34~+cells isolated with magnetic beads were incubated in serum-free medium containing TPO for 60 days with weekly changes of half of the medium. The expanded cells were incubated in neurobasal medium containing N-2 supplement. The expression of CD226 and lymphocyte function associated antigen-1 (LFA-1) (CDlla, a subunit of LFA-1 molecule, were investigated during proliferation and differentiation toward granulocyte-lineage, megakaryocyte-lineage and erythroid-lineage. The effect of CD226 monoclonal antibody (MoAb) and LFA-1 MoAb on megakaryocytes was studied with antibody cross-liking technique. We also investigated the expression of CD226 molecule, hemopoiesis related antigens and neural cell related antigens on the FL derived-CD34+cells induced to differentiate toward neural cells with flow cytometry and immunocytochemistry. [Results] CD34~+ cells from adult and fetus and TPO-induced CD41~+ cells allexpressed CD226 molecule. However, CD226 was not expressed on erythroidprogenitor cells and erythroblasts and most cells of granulocytic lineage although G-CSF induced a significant increase of the expression of CD226 on CD34~+ cells in the early period of time during their differentiation toward granulocyte-lineage. CD226 MoAb acts on megakaryocytes by inducing intracellular calcium mobilization. The expression of LFA-1 decreased significantly at late stage of differentiation and maturation of fetal megakaryocytes whereas the expression of LFA-1 on adult megakaryocytes retained at a high level. Moreover, CD226 MoAb in combination with LFA-1 MoAb can shift the ploidy of generated megakaryocytes from adult-derived CD34~+ cells to higher classes significantly although CD226 and LFA-1 MoAb...