title: Expression of tumour necrosis factor-alpha in the rat dental follicle.
abstract: Tooth eruption requires the presence of the dental follicle, a loose connective tissue sac that surrounds each unerupted tooth. The follicle appears to regulate many of the cellular and molecular events of eruption, including the formation of osteoclasts needed to resorb alveolar bone to form an eruption pathway. To that end, the expression of the tumour necrosis factor-alpha (TNF-alpha) gene was examined in the dental follicle as a possible regulator of osteoclastogenesis. TNF-alpha was expressed slightly in the dental follicle of the first mandibular molar of the rat beginning at day 3 postnatally, but maximal expression was seen at day 9, a time that correlates with a slight burst of osteoclast formation seen at day 10 postnatally. In vitro, TNF-alpha was not expressed constitutively in the follicle cells but incubating them with interleukin 1alpha resulted in a strong expression of TNF-alpha after only 0.5h. TNF-alpha itself enhanced monocyte chemotactic protein 1 (MCP-1) and vascular endothelial growth factor (VEGF) gene expression. It also slightly decreased the expression of osteoprotegerin after 3-h incubation but this returned to the control level at 6h. MCP-1 and VEGF could aid in recruiting mononuclear cells (osteoclast precursors) to the dental follicle. In addition to the potential role of TNF-alpha in tooth eruption, this study suggests that the periodontal ligament derived from the dental follicle might have the capacity to synthesize TNF-alpha, and thereby contribute to the destructive events of periodontitis.
authors.affiliation: Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA. gwise@vetmed.lsu.edu <gwise@vetmed.lsu.edu>
authors.forename: Gary E
authors.initials: GE
authors.lastname: Wise
authors.forename: Shaomian
authors.initials: S
authors.lastname: Yao
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism; D003795:Dental Sac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D016228:Endothelial Growth Factors / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D007375:Interleukin-1 / Q000494:pharmacology; D008222:Lymphokines / Q000378:metabolism; D010010:Osteoclasts / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014078:Tooth Eruption / Q000235:genetics / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000235:genetics* / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
chemical_list: D018932:Chemokine CCL2; D016228:Endothelial Growth Factors; D036341:Intercellular Signaling Peptides and Proteins; D007375:Interleukin-1; D008222:Lymphokines; D014409:Tumor Necrosis Factor-alpha; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors