Regulation of secretion of osteoprotegerin in rat dental follicle cells.
Tooth eruption requires alveolar bone resorption and formation, both of which appear to be regulated by the dental follicle. Osteoclastogenesis needed for this bone resorption appears to occur as a result of a reduction in the expression of the osteoprotegerin (OPG) gene in the dental follicle at a specific time. This reduction in expression is mediated in vitro in the follicle cells by colony-stimulating factor-1 (CSF-1) and parathyroid hormone-related protein (PTHrP). Using enzyme-linked immunosorbent assays and immunoblotting, this study shows that the reduction in expression of OPG after incubation of the dental follicle cells in either CSF-1 or PTHrP also results in a reduction in its secretion. We also show, by laser capture microdissection, that PTHrP is expressed in vivo in the stellate reticulum such that it could inhibit OPG expression via a paracrine effect on the follicle. Bone formation is enhanced by OPG secretion, and incubation of the follicle cells with bone morphogenetic protein-2 (BMP-2) enhances OPG secretion. Thus, a reduction in secretion of the OPG protein at defined times may promote the osteoclastogenesis and alveolar bone resorption needed for eruption, and enhancement of OPG secretion at other times may promote alveolar bone formation.
Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA. gwise@vetmed.lsu.edu
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D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology; D001862:Bone Resorption / Q000378:metabolism; D002478:Cells, Cultured; D003795:Dental Sac / Q000187:drug effects / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D006023:Glycoproteins / Q000032:analysis / Q000378:metabolism*; D015151:Immunoblotting; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D042282:Microdissection; D010010:Osteoclasts / Q000187:drug effects; D053244:Osteoprotegerin; D019899:Paracrine Communication; D044162:Parathyroid Hormone-Related Protein / Q000494:pharmacology; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis; D018124:Receptors, Tumor Necrosis Factor / Q000032:analysis / Q000378:metabolism*; D014078:Tooth Eruption; D016212:Transforming Growth Factor beta / Q000494:pharmacology
C525720:Bmp2 protein, rat; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D006023:Glycoproteins; D053244:Osteoprotegerin; D044162:Parathyroid Hormone-Related Protein; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C506032:Tnfrsf11b protein, rat; D016212:Transforming Growth Factor beta; D016173:Macrophage Colony-Stimulating Factor