BACKGROUNDNowadays bone marrow represents the main source of mesenchymal stem cells (MSCs). We identified a new population of MSCs derived from human placenta and compared its biological characterization with bone marrow derived MSCs.

METHODSMononucleated cells (MNC) were isolated from the human placenta tissue perfusate by density gradient fractionation. Individual colonies were selected and cultured in tissue dishes. At the same time, human bone marrow derived MSCs were identified. Culture-expanded cells were characterized by immune phenotyping and cultured under conditions promoting differentiation to osteoblasts or adipocytes. The hematopoietic cytokines were assayed using reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTSHuman placental MSCs exhibited fibroblastoid morphology. Flow cytometric analyses showed that the placental MSC were CD29, CD44, CD73, CD105, CD166, HLA-ABC positive; but were negative for CD34, CD45, and HLA-DR. Functionally, they could be induced into adipocytes or osteocytes. Moreover, several hematopoietic cytokine mRNA was found in placenta-derived MSCs by RT-PCR analysis, including IL-6, M-CSF, Flt3-ligand and SCF. These results were consistent with the properties of bone marrow derived MSCs.

CONCLUSIONThese observations implicate the postpartum human placenta as an important and novel source of multipotent stem cells that could potentially be used for investigating mesenchymal differentiation and regulation of hematopoiesis.