Figure 4.

Continuous expression of exogenous genes introduced via the PB system in the absence of the selective drug. (a) A flowchart of depicting the characterization of transfectants cultured over a long period. (b) Fluorescence in HDDPC-GR-1 cells cultured in a scaffold for three months. The scaffold was cut in half, and the inner surface was inspected under a fluorescence microscope. Several clusters of cells with both red and green fluorescence (arrows) were apparent. Bar = 50 μm. (c) RT-PCR analysis of HDDPC-GR-1 cells before and after the long cultivation. After isolation of mRNA, cDNA was synthesized using oligo(dT) and then used for PCR. -RT, RT-PCR using water as template; M, 100-bp ladder markers; DSPP, dentin sialophosphoprotein; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; EGFP, enhanced green fluorescent protein; HDDPC, human deciduous tooth dental pulp cell; RT-PCR, reverse transcriptase-polymerase chain reaction.