title: Contribution of mesenchymal proliferation in tooth root morphogenesis.
abstract: In mouse tooth development, the roots of the first lower molar develop after crown formation to form 2 cylindrical roots by post-natal day 5. This study compared the morphogenesis and cellular events of the mesial-root-forming (MRF) and bifurcation-forming (BF) regions, located in the mesial and center of the first lower molar, to better define the developmental mechanisms involved in multi-rooted tooth formation. We found that the mesenchyme in the MRF showed relatively higher proliferation than the bifurcation region. This suggested that spatially regulated mesenchymal proliferation is required for creating cylindrical root structure. The mechanism may involve the mesenchyme forming a physical barrier to epithelial invagination of Hertwig's epithelial root sheath. To test these ideas, we cultured roots in the presence of pharmacological inhibitors of microtubule and actin polymerization, nocodazole and cytochalasin-D. Cytochalasin D also inhibits proliferation in epithelium and mesenchyme. Both drugs resulted in altered morphological changes in the tooth root structures. In particular, the nocodazole- and cytochalasin-D-treated specimens showed a loss of root diameter and formation of a single-root, respectively. Immunolocalization and three-dimensional reconstruction results confirmed these mesenchymal cellular events, with higher proliferation in MRF in multi-rooted tooth formation.
authors.affiliation: Department of Biochemistry, School of Dentistry, IHBR, Kyungpook National University, Daegu, Korea.
authors.forename: W-J
authors.initials: WJ
authors.lastname: Sohn
authors.forename: M-A
authors.initials: MA
authors.lastname: Choi
authors.forename: H
authors.initials: H
authors.lastname: Yamamoto
authors.forename: S
authors.initials: S
authors.lastname: Lee
authors.forename: Y
authors.initials: Y
authors.lastname: Lee
authors.forename: J-K
authors.initials: JK
authors.lastname: Jung
authors.forename: M-U
authors.initials: MU
authors.lastname: Jin
authors.forename: C-H
authors.initials: CH
authors.lastname: An
authors.forename: H-S
authors.initials: HS
authors.lastname: Jung
authors.forename: J-Y
authors.initials: JY
authors.lastname: Suh
authors.forename: H-I
authors.initials: HI
authors.lastname: Shin
authors.forename: J-Y
authors.initials: JY
authors.lastname: Kim
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002452:Cell Count; D049109:Cell Proliferation / Q000187:drug effects; D015638:Cytochalasin D / Q000494:pharmacology; D003795:Dental Sac / Q000166:cytology / Q000254:growth & development; D004658:Enamel Organ / Q000166:cytology / Q000254:growth & development; D004848:Epithelium / Q000187:drug effects / Q000254:growth & development; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D019394:Ki-67 Antigen / Q000032:analysis; D008648:Mesoderm / Q000166:cytology* / Q000187:drug effects; D051379:Mice; D008813:Mice, Inbred ICR; D008963:Molar / Q000166:cytology / Q000187:drug effects / Q000254:growth & development*; D009024:Morphogenesis / Q000187:drug effects / Q000502:physiology*; D015739:Nocodazole / Q000494:pharmacology; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D009805:Odontogenesis / Q000187:drug effects / Q000502:physiology; D009924:Organ Culture Techniques; D014092:Tooth Root / Q000166:cytology / Q000187:drug effects / Q000254:growth & development*; D050257:Tubulin Modulators / Q000494:pharmacology
chemical_list: D019394:Ki-67 Antigen; D019384:Nucleic Acid Synthesis Inhibitors; D050257:Tubulin Modulators; D015638:Cytochalasin D; D015739:Nocodazole
keywords: cell proliferation; histochemistry; molar; odontogenesis; tooth development; tooth root