MRC-5, human fetal lung fibroblast cell line was obtained from the American Type Culture Collection (Manassas, VA 20108, USA). All cultures were maintained in a phenol red free culture medium DMEM/F12 (Dulbecco’s modified essential medium/Ham’s 12 nutrient mixture, Gibco), supplemented with 5% (vol/vol) fetal calf serum (JS Bioscience, Australia), and 1% (vol/vol) antibiotic (2 mM l-glutamine, 100 U/mL Penicillin and 100 μg/mL Streptomycin; Gibco). Cultured cells were kept at 37 °C in a humidified 5% carbon dioxide (CO2) incubator. Once the cells reached confluence, the culture medium was removed from the flask and the cells were rinsed three times with sterile HBSS (Hank’s Balanced Salt Solution, Gibco). The confluent cell layers were enzymatically removed, using Trypsin/EDTA (Gibco, USA), and resuspended in culture medium. Cell viability was assessed by vital staining with trypan blue (0.4% (wt/vol); Sigma, USA), and cell numbers were determined using a light microscope (Leitz Wetzlar, Germany).