Platelets are produced from megakaryocytes (MKs) although the pathway leading from stem cells to MK lineages are not yet fully understood Recently we reported to obtain abundant MKs and platelets from human subcutaneous adipose tissues Adipose tissues contain various cell types most of which are lineage cells from mesenchymal or adipocyte-derived stem cells distinct from hematopoietic cells To identify the cells responsible for the differentiation MK lineages in adipose tissues this study examined whether the preadipocyte cell line 3T3-L1 and fibroblast cell line 3T3 differentiated into MK lineages in vitro Cells were cultured in megakaryocyte lineage induction medium By day 4 most of 3T3 cell-derived cells leaded to cell death In contrast 3T3-L1-derived cells on days 8 showed to have typical characterizations of MK lineages in analyses for specific marker DNA ploidy transmission electro micrograph 3T3-L1-derived platelet-sized cells on day 12 could be stimulated by ADP and PAR4-activating peptide This study clearly shows in vitro differentiation from 3T3-L1 cells not from 3T3 cells Into MK lineages (C) 2010 Elsevier Inc All rights reserved