Figure 4. Expression of bone and dentin extracellular matrix (ECM)-related genes analyzed by reverse-transcriptase polymerase chain-reaction (RT-PCR). (A) A representative electrophoresis image visualized with ethidium bromide staining from triplicate PCR trials. (B) The expression time-course for each gene. The intensity of bands was normalized relative to the GAPDH expression level, and further normalized with respect to the lowest expression level of all detected bands.