title: Immunohistochemical localization of alpha-Smooth muscle actin during rat molar tooth development.
abstract: The dental follicle contains mesenchymal cells that differentiate into osteoblasts, cementoblasts, and fibroblasts. However, the characteristics of these mesenchymal cells are still unknown. alpha-Smooth muscle actin (alpha-SMA) is known to localize in stem cells and precursor cells of various tissues. In the present study, to characterize the undifferentiated cells in the dental follicle, immunohistochemical localization of alpha-SMA was examined during rat molar tooth development. Rat mandibles were collected at embryonic days (E) 15-20 and postnatal days (P) 7-28. Immunohistochemical stainings for alpha-SMA, periostin, Runt-related transcription factor-2 (Runx2), tissue nonspecific alkaline phosphatase (TNAP), and bone sialoprotein (BSP) were carried out using paraffin-embedded sections. alpha-SMA localization was hardly detected in the bud and cap stages. At the early bell stage, alpha-SMA-positive cells were visible in the dental follicle around the cervical loop. At the late bell to early root formation stage (P14), these cells were detected throughout the dental follicle, but they were confined to the apical root area at P28. Double immunostaining for alpha-SMA and periostin demonstrated that alpha-SMA-positive cells localized to the outer side of periostin-positive area. Runx2-positive cells were visible in the alpha-SMA-positive region. TNAP-positive cells in the dental follicle localized nearer to alveolar bone than Runx2-positive cells. BSP was detected in osteoblasts as well as in alveolar bone matrix. These results demonstrate that alpha-SMA-positive cells localize on the alveolar bone side of the dental follicle and may play a role in alveolar bone formation.
authors.affiliation: Department of Oral Histology, Matsumoto Dental University, 1780 Gobara Hirooka, Shiojiri, Nagano 399-0781, Japan. hosoya@po.mdu.ac.jp
authors.forename: Akihiro
authors.initials: A
authors.lastname: Hosoya
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nakamura
authors.forename: Tadashi
authors.initials: T
authors.lastname: Ninomiya
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Yoshiba
authors.forename: Nagako
authors.initials: N
authors.lastname: Yoshiba
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nakaya
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Wakitani
authors.forename: Hirohito
authors.initials: H
authors.lastname: Yamada
authors.forename: Etsuo
authors.initials: E
authors.lastname: Kasahara
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Ozawa
mesh_terms: D000199:Actins / Q000032:analysis*; D000818:Animals; D007150:Immunohistochemistry; D008963:Molar / Q000737:chemistry / Q000254:growth & development*; D051381:Rats; D017208:Rats, Wistar; D014083:Tooth Germ / Q000737:chemistry / Q000254:growth & development*; D014092:Tooth Root / Q000737:chemistry / Q000254:growth & development*
chemical_list: D000199:Actins; C498862:Acta2 protein, rat