RT-PCR detection of APP, neprilysin, and β-secretase in human RPE cells. Human RPE cells were cultured in DMEM containing 10% FCS. After cellular confluence, total RNA was extracted from cultured RPE cells. The cDNA was synthesized from 2 μg of total RNA, and the reaction product was subjected to PCR amplification using specific primers for APP, neprilysin, and β-secretase.