title: Insulin-like growth factor-I stimulates cell proliferation in the outer layer of Hertwig's epithelial root sheath and elongation of the tooth root in mouse molars in vitro.
abstract: To elucidate the mechanism of root formation in tooth development, we examined the role of insulin-like growth factor I (IGF-I) on early root formation in mandibular first molar teeth from 5-day-old mice. Immunohistochemistry revealed the specific localization of the IGF-I receptor in Hertwig's epithelial root sheath (HERS) in the tooth root. The effect of IGF-I on root development, especially on HERS, was subsequently examined in vitro. The control culture showed normal development of HERS and the periodontium, resembling that in vivo. However, the presence of 100 ng/ml IGF-I resulted in elongation of HERS and increased cell proliferation in its outer layer. These effects were negated by the addition of antibodies specific for IGF-I. Thus, we propose that IGF-I is involved in early root formation by regulating the mitotic activity in the outer layer of HERS.
authors.affiliation: Department of Oral Anatomy II, School of Dentistry, Iwate Medical University, 1-3-27, Chuo-dori, Morioka, Iwate, 020-8505, Japan. naokif@iwate-med.ac.jp
authors.forename: Naoki
authors.initials: N
authors.lastname: Fujiwara
authors.forename: Makoto J
authors.initials: MJ
authors.lastname: Tabata
authors.forename: Makoto
authors.initials: M
authors.lastname: Endoh
authors.forename: Kiyoto
authors.initials: K
authors.lastname: Ishizeki
authors.forename: Tokio
authors.initials: T
authors.lastname: Nawa
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects*; D004658:Enamel Organ / Q000254:growth & development*; D004848:Epithelium / Q000254:growth & development; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008334:Mandible / Q000254:growth & development; D051379:Mice; D008815:Mice, Inbred Strains; D008963:Molar / Q000254:growth & development; D009924:Organ Culture Techniques / Q000379:methods*; D014092:Tooth Root / Q000254:growth & development*
chemical_list: D007334:Insulin-Like Growth Factor I