Effect of glycerol on reconstructed human oral mucosa

The majority of severely ill patients experience dry mouth. For institutionalized patients, this condition is commonly treated using glycerol as a lubricant. However, because of its possibly desiccating effect, some countries do not advocate the use of glycerol. This study aimed to investigate dose-dependent effects of glycerol on homeostasis and tissue integrity of in vitro-reconstructed normal human buccal mucosa (RNHBM). Primary keratinocytes and fibroblasts were isolated and expanded from biopsies of mucosa from eight healthy volunteers. Ninety-six samples of RNHBM were prepared and exposed for 24 h to 17%, 42.5%, or 85% glycerol, or to distilled H₂ O (control). Sections were stained with haematoxylin and eosin (H&E) to evaluate epithelial thickness or used for immunohistochemistry to measure expression of Ki67 (proliferation), cleaved caspase-3 (apoptosis), and E-cadherin (tissue-integrity). Positive cells and cell layers, as detected by immunohistochemistry, were counted. Epithelial thickness, proliferation, and apoptosis were significantly increased by exposure to 42.5% and 85% glycerol. No significant differences in apoptosis or proliferation were found between controls and RNHBM exposed to 17% glycerol. E-cadherin expression was not significantly affected by exposure to any of the concentrations of glycerol tested. This study shows that glycerol affects tissue homeostasis, but not tissue integrity, of RNHBM at glycerol concentrations above 42.5%.