Transdifferentiation of Bone Marrow-Derived Cells Co-Cultured with Fetal Liver Cells into Hepatic-Like Cells without Fusion.

Several research groups have reported that bone marrow cells (BMCs) transdifferentiate into hepatocytes in rodents. However, it is yet to be studied what factors effectively trigger and sustain the transdifferentiation of BMCs to hepatocytes. In the present study, we investigated whether murine BMCs in the presence of fetal liver cells (FLCs) could differentiate into hepatic-like cells in vitro without fusion. Fractionated BMCs from C57Bl/6-TgN(ACTbEGFP)10bs mice and FLCs from B6.129S7-Gt(ROSA)26Sor mice were co-cultured at 1x10⁵ cells and 1x10⁶ cells in 10% FCS-containing medium supplemented with hepatocyte growth factor on laminin-coated dishes. Hepatocyte-specific markers among BMCs were detected as assessed by immunocytochemistry for albumin and reverse transcription-polymerase chain reaction (RT-PCR) for alpha-fetoprotein (AFP), albumin, and cytokeratin-19 mRNAs. We also found that Sca-1⁺ BMCs containing both hematopoietic stem cells and AFP-expressing cells could differentiate into hepatic-like cells and such cells were seen adherent to dish together with FLCs in the early phase of culture. Moreover, the AFP-expressing cells were found in a Sca-1⁺ cKit^- cell fraction, which also differentiated into CD45⁻ GFP⁺ albumin⁺ cells and proved to be positive for GFP but negative for LacZ as assessed by RT-PCR and immunocytochemistry. These results suggest that albumin⁺ cells developed through transdifferentiation from BMCs but not through spontaneous cell fusion between BMCs and FLCs.