In vitro evaluation of inhibitory effect on cell-death by dryness

Objectives: Some clinical studies have reported relief of dry mouth with certain products. However, few studies have examined the efficacies of such products or their ingredients at cellular level in vitro. The purpose of this study was to evaluate inhibitory effects of certain materials on cell death due to dryness using human gingival epithelial cells in vitro. Methods: Human gingival epithelial cell line Ca9-22 was cultured and treated with the following samples: 20 polysaccharides, 2 oligosaccharides, 5 sugar alcohols, and 4 polyhydric alcohols. After removal of sample, cells were incubated under dry conditions (25°C, 30% humidity). Following these treatments, relative cell survival rate was determined by alamarBlue assay to control group which was treated with PBS. Inhibition of cell death was tested with both short-term and long-term treatments with samples. In shot-term treatment, cells were treated with samples for 15 minutes after removal of medium from confluent cells. In long-term treatment, cells were treated with samples for 3 days in medium during culture to confluence. Results: On short-term treatment, natural polysaccharides (xanthan gum, gellan gum), synthetic polysaccharides (hydroxypropylcellulose, methyl cellulose, ethyl cellulose) and a polyhydric alcohol (glycerin), and in long-term treatment, an oligosaccharide (glycosyltrehalose; Tornare®) yielded high survival rates about twice that in control group and exhibited inhibitory effects on cell death respectively. Since effective materials differed with the two treatments, their modes of action might differ. Both types of materials could be effective component for relieving symptoms of xerostomia. Conclusion: In this study, inhibition of cell death due to dryness was evaluated using a cultured cell line derived human gingival epithelia in vitro with both of short-term and long-term treatments. Six materials on short-term treatment and one material on long-term treatment exhibited inhibitory effects on cell death caused by dryness.