Comparative Cytotoxic Effects of Short-chain Fatty Acids Produced by Periodontal Pathogens on Two Cultured Fibroblast Lines

Abstract

The cytotoxic effects of a range of short-chain fatty acids produced by anaerobic periodontopathic bacteria were compared using two types of fibroblast culture: Vero cells and human gingival fibroblasts. Morphological changes in cells exposed to 1.56—25 mM acetic, n-butyric, isobutyric, n-caproic, isocaproic, phenylacetic, propionic, n-valeric and isovaleric acids for three days were monitored using phase contrast microscopy and metabolic activity of cultures assessed by measuring reduction of the tetrazolium salt MTT. Vero cells were considerably more sensitive than human gingival fibroblasts to both morphological and metabolic changes. Reduction in metabolic activity of Vero cells was n-butyric > propionic, n-valeric and isovaleric > phenylacetic, n-caproic and isocaproic. N-butyric acid (≥ 12.5 mM) caused progressive cell rounding and death of >90 per cent of the cells by three days. Exposure to n-caproic, n-valeric and isovaleric acids (25 mM) produced spindle-shaped Vero cells with one or more long dendritic projections and reduced metabolic activity to ≤60 per cent of control values ( P <0.001). Comparable morphological changes were not observed in human gingival fibroblasts exposed to the maximum concentrations of any acid and only n-butyric, propionic and phenylacetic acids reduced metabolic activity significantly. Thus although Vero cells have traditionally been used to test for the cytotoxic effects of potential virulence factors from periodontal pathogens, their behaviour may not be representative of the cells normally exposed to these components in vivo . Keywords - Cytotoxicity, Short-chain fatty acids, Human gingival fibroblasts, MTT, Vero cells.