Bone marrow (BM) cells from green fluorescent protein (GFP) transgenic mice were transplanted into age-matched C57BL/J mice. GFP-expressing cells with intracytoplasmic lipid droplets comprised 33.4 +/- 2.3% of the cells isolated by density gradient centrifugation. These cells expressed the hepatic stellate cells (HSCs) lineage markers, such as desmin and glial fibrillary acidic protein (GFAP), by both RT-PCR and immunostaining. During a 7-day culture, GFP-positive cells began to express alpha-smooth muscle actin, a marker of activated HSCs. In the liver of BM-transplanted mice, GFP-positive nonparenchymal cells expressed GFAP and extended their process around hepatocytes. Upon liver injury, these cells also co-expressed desmin and alpha-smooth muscle actin.