Mechanism of Endotoxin Inhibition of Human Gingival Fibroblast Attachment to Type I Collagen

Abstract

Bacterial endotoxin inhibits the attachment of human gingival fibroblasts to collagen. The present study attempted to elucidate the possible mechanism of this inhibition. Two mechanisms were considered: direct toxicity to the cells and steric interference. Collagen substrates were prepared by rat type I collagen being air-dried in the wells of 24 multi-well plates. Experimental collagen substrates were treated with 50 micrograms of endotoxin/well, while untreated collagen substrates served as controls. Two mL of cell suspension (10(4) cells/mL) was added to each well, and these were incubated at 37 degrees C for two h. The average cell number/mm2 attached to experimental and control substrates was determined. Cell attachment to endotoxin-treated collagen was inhibited by 78%, compared with that to untreated collagen. The washing of the endotoxin-treated collagen for two h did not affect the inhibition of cell attachment, whereas after 24 h of washing, cell attachment was inhibited by 54%, compared with that to untreated collagen. Pre-incubation of the cells in endotoxin for two h did not affect their attachment to collagen. The addition of fetal calf serum (15%) to the experimental system completely reversed the inhibition of fibroblast attachment to endotoxin-treated collagen. These findings suggest that endotoxin interferes with fibroblast attachment to collagen through a steric phenomenon, possibly by blocking the binding sites on the collagen molecule recognized by the membrane receptor for collagen.

Cell Attachment Activity of Cementum Proteins and Mechanism of Endotoxin Inhibition

“…Inhibitors other than endotoxins may be present, or the endotoxin may coat the root surface, blocking its access to the cells. If the root surface is damaged, exposing collagen fibrils, the endotoxin may bind to exposed collagen, thus preventing fibroblast attachment to collagen (Pitaru et al, 1990). Additional experiments with healthy and diseased root surfaces are necessary for the precise mechanism to be determined.…”