Effect of a lipopolysaccharide from E. coli on the proliferation of fibroblasts and keratinocytes in vitro.

Studies previously conducted in our laboratory have shown that an extract from the leaves of Chromo-laena odorata is mitogenic for human skin fibroblasts and keratinocytes. However, lipopolysaccharides, sometimes present in plant extracts, can also play a role in cell growth and might have been responsible for or contributed to the mitogenic activity observed. The present study aimed to investigate whether a lipopolysaccharide would have any effect on the proliferation of human fibroblasts and keratinocytes. Cells were seeded in 96-well plates and concentrations from 0.0 to 5.0 microg/mL of lipopolysaccharide in basal or growth medium were added. Cell growth was determined over a period of 10 days using a colorimetric assay. Lipopolysaccharide at concentrations between 0.05 microg/mL and 0.5 microg/mL in the growth medium significantly stimulated fibroblast proliferation after incubation for more than 6 days. In basal medium, more than 8 days of incubation was needed for significant stimulation of growth. Lipopolysaccharide stimulation of keratinocytes was evident at 0.5 microg/mL by day 3 in basal medium and by day 5 in growth medium. Although the lipopolysaccharide did stimulate cell growth it did so only at higher concentrations than were present in our plant extracts and to a lesser degree.