Mesenchymal stem cells (MSC) have been derived from different sources, including bone marrow and liver. To further support the hypothesis that MSC may also exist in most postnatal tissues, we isolated a clonogenic, multipotent, rapidly proliferating population of cells from a fetal liver and defined them as mesenchymal-like stem cells (FL-MLSC) derived from human fetal liver. In this study, FACS analysis showed that FL-MLSC are positive for CD105 (endoglin/SH-2), CD73 (5′ terminal nucleotidase/SH-3), CD166 (ALCAM-1), CD44 (the hyaluronate receptor), HLA class-I(HLA-ABC), CDw90 (thy-1), CD13, and CD106 but negative for CD34 and HLA class-II(HLA-DR). Cell-cycle analysis showed that more than 81.9% cells were arrested in G0 and G1 phases, whereas an only small subpopulation of cells was actively engaged in proliferation (S + G2 + M = 18%) and doubling in about 48 hours. FL-MLSC retained normal diploid karyotypes and growth characteristics over the successive culture. In addition, under differentiation culture conditions, these cells showed the capability of differentiation into various cell types including chondrogenic, adipogenic, osteogenic, neuronal and endocrine lineages. These results demonstrated that FL-MLSC could be isolated from human fetal livers by means of their adherent ability and suggested that they were capable of self-renewal and multipotent differentiation.

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