Evidence for a dentin-derived inhibitor of macrophage spreading.

The ability of macrophages to spread in vitro on mineralized and non-mineralized tissues extracted with guanidium hydrochloride (GuHCl) was studied in order to establish morphologic evidence for an extractable inhibitor of macrophage spreading present within dentin. Macrophages were seeded onto dentin, demineralized dentin, predentin and hyaline cartilage extracted with different concentrations of GuHCl. Macrophages were also seeded onto unextracted tissues. The results were evaluated with scanning electron microscopy after varying incubation periods. Macrophages readily attached and spread on extracted and unextracted dentin, extracted demineralized dentin, predentin, and hyaline cartilage. Cells seeded onto unextracted demineralized dentin, predentin, and hyaline cartilage attached, but showed no signs of spreading. It was concluded that an extractable inhibitor of macrophage spreading is present in the organic, non-collagenous component of dentin. This inhibitor may be responsible for the resistance of predentin and dentin to resorption.