The number of viable cells was evaluated based on the amount of ATP by using a CellTiter-Glo Luminescent Cell Viability Assay using a Veritas Microplate Luminometer (Promega, Fitchburg, WI, USA) according to manufacturer's protocol. Six samples were prepared for each group.
DNA synthesis was detected as incorporation of 5-bromo-2deoxyuridine (BrdU) using the Cell Proliferation Biotrak ELISA system, version 2 (GE Healthcare Life Sciences, Buckinghamshire, UK) according to the manufacturer's instructions. Briefly, HCECs were incubated with 10 lmol/L BrdU for 24 hours, further incubated with fixation solution (Amersham Biosciences, Freiburg, Germany) for 2 hours, and incubated with 100 ll of monoclonal antibody against BrdU for 30 minutes. The BrdU After washing with TBS-T buffer, the blots were incubated with horseradish peroxidase-conjugated secondary antibodies (1:5000: anti-rabbit, anti-mouse IgG; Cell Signaling Technology). The blots were developed with luminal for enhanced chemiluminescence (ECL) using the Chemi-Lumi One Ultra (Nacalai Tesque), documented by LAS4000S (Fuji Film, Tokyo, Japan), and analyzed with Image Gauge software (Fuji Film).