Stable transfection of MSCs by electroporation

Human marrow stromal cells (hMSCs) are an attractive source of adult stem cells for autologous cell and gene therapy. To transfect hMSCs without the use of viruses, we developed improved conditions for stable transfection of the cells by electroporation. hMSCs were isolated by adherence to plastic, and were electroporated at 600 V and 100 μs in a 2-mm gap cuvette with a plasmid containing enhanced green fluorescence protein (EGFP) and neomycin phosphotransferase gene (neor). After electroporation of 106 cells with 10 μg of the linearized plasmid DNA, hMSCs with stable DNA integration were selected by culturing with 200 μg/ml G418. The transfected hMSCs were expanded another 300-fold in 14 days to obtain 89 million cells, of which 98% expressed EGFP. Chloroquine increased the number of hMSCs transiently expressing EGFP from 12% to over 50%, but decreased stable integration. Stable integration of plasmid DNA into rat MSCs by electroporation was also successful. The transfected MSCs retained their capacity to differentiate into both adipocytes and osteoblasts. Thus, MSCs were stably transfected with plasmid DNA and retained their differentiation capacity after expansion.