Colony-stimulating factor-1 and monocyte chemotactic protein-1 chemotaxis for monocytes in the rat dental follicle

Tooth eruption requires the influx of mononuclear cells (monocytes) into the dental follicle to form osteoclasts that resorb the alveolar bone to form an eruption pathway. Candidate molecules to attract these monocytes are colony-stimulating factor-1 (CSF-1) which is produced in the dental follicle, and monocyte chemotactic protein-1 (MCP-1), which is known to be a chemoattractant for monocytes. Using reverse transcription-polymerase chain reaction techniques, it was shown that the follicle cells of the first mandibular molar of the rat transcribe MCP-1 with maximal expression in vivo at day 3 postnatally, the time of peak expression of CSF-1 as well. This is also the day of peak influx of monocytes into the follicle. To determine if these molecules that were produced by the dental follicle were chemotactic, a chemotactic assay using a mouse monocyte cell line was conducted. CSF-1 or MCP-1 alone were found to be chemotactic for the monocytes and conditioned medium from the cultured follicle cells also was chemotactic. Incubating the conditioned medium with antibodies against either CSF-1 or MCP-1 reduced the chemotaxis. The results demonstrate that both CSF-1 and MCP-1 produced by the dental follicle are chemotactic for monocytes and that these chemoattractants might be responsible for the influx of monocytes into the follicle necessary to initiate tooth eruption.