PDGFs regulate tooth germ proliferation and ameloblast differentiation.
OBJECTIVE
The purpose of this study was to elucidate the effects of platelet-derived growth factors (PDGFs) during tooth development, as well as the mechanisms underlying the interactions of growth factors with PDGF signalling during odontogenesis.


METHODS
We used an ex vivo tooth germ organ culture system and two dental cell lines, SF2 cells and mDP cells, as models of odontogenesis. AG17, a tyrosine kinase inhibitor, was utilised for blocking PDGF receptor signalling. To analyse the expressions of PDGFs, reverse transcriptase (RT)-PCR and immunohistochemistry were performed. Proliferation was examined using a BrdU incorporation assay for the organ cultures and a cell counting kit for the cell lines. The expressions of Fgf2 and ameloblastin were analysed by real-time RT-PCR.


RESULTS
The PDGF ligands PDGF-A and PDGF-B, and their receptors, PDGFRalpha and PDGFRbeta, were expressed throughout the initial stages of tooth development. In the tooth germ organ cultures, PDGF-AA, but not PDGF-BB, accelerated cusp formation. Conversely, AG17 suppressed both growth and cusp formation of tooth germs. Exogenous PDGF-BB promoted mDP cell proliferation. Furthermore, PDGF-AA decreased Fgf2 expression and increased that of ameloblastin, a marker of differentiated ameloblasts.


CONCLUSIONS
Our results indicate that PDGFs are involved in initial tooth development and regulate tooth size and shape, as well as ameloblast differentiation.
Wu
Nan
N
Division of Oral Health, Growth and Development, Faculty of Dental Science, Kyushu University, Fukuoka, Japan.
Iwamoto
Tsutomu
T
Sugawara
Yu
Y
Futaki
Masaharu
M
Yoshizaki
Keigo
K
Yamamoto
Shinya
S
Yamada
Aya
A
Nakamura
Takashi
T
Nonaka
Kazuaki
K
Fukumoto
Satoshi
S
D000565:Ameloblasts / Q000166:cytology*; D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D003746:Dental Enamel Proteins / Q000096:biosynthesis / Q000235:genetics; D004847:Epithelial Cells / Q000166:cytology; D016222:Fibroblast Growth Factor 2 / Q000096:biosynthesis / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D008648:Mesoderm / Q000166:cytology; D051379:Mice; D008813:Mice, Inbred ICR; D009805:Odontogenesis / Q000235:genetics*; D009924:Organ Culture Techniques; D010982:Platelet-Derived Growth Factor / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology*; D017479:Receptors, Platelet-Derived Growth Factor / Q000502:physiology*; D015398:Signal Transduction; D019228:Tooth Crown / Q000254:growth & development; D014083:Tooth Germ / Q000166:cytology* / Q000196:embryology
C490890:Ambn protein, mouse; D003746:Dental Enamel Proteins; D010982:Platelet-Derived Growth Factor; D016222:Fibroblast Growth Factor 2; D017479:Receptors, Platelet-Derived Growth Factor