Dynamic analysis of the expression of the TGFbeta/SMAD2 pathway and CCN2/CTGF during early steps of tooth development.
OBJECTIVE
CCN2 is present during tooth development. However, the relationship between CCN2 and the transforming growth factor beta (TGFbeta)/SMAD2/3 signaling cascade during early stages of tooth development is unclear. Here, we compare the expression of CCN2 and TGFbeta/SMAD2/3 components during tooth development, and analyze the functioning of TGFbeta/SMAD2/3 in wild-type (WT) and Ccn2 null (Ccn2-/-) mice.


METHODS
Coronal sections of mice on embryonic day (E)11.5, E12.5, E13.5, E14.5 and E18.5 from WT and Ccn2-/- were immunoreacted to detect CCN2 and components of the TGFbeta signaling pathway and assayed for 5'-bromo-2'-deoxyuridine immunolabeling and proliferating cell nuclear antigen immunostaining.


RESULTS
CCN2 and TGFbeta signaling components such as TGFbeta1, TGFbeta receptor II, SMADs2/3 and SMAD4 were expressed in inducer tissues during early stages of tooth development. Proliferation analysis in these areas showed that epithelial cells proliferate less than mesenchymal cells from E11.5 to E13.5, while at E14.5 they proliferate more than mesenchymal cells. We did not find a correlation between functioning of the TGFbeta1 cascade and CCN2 expression because Ccn2-/- mice showed neither a reduction in SMAD2 phosphorylation nor a difference in cell proliferation.


CONCLUSIONS
CCN2 and the TGFbeta/SMAD2/3 signaling pathway are active in signaling centers of tooth development where proliferation is dynamic, but these mechanisms may act independently.
Pacheco
Marcos S
MS
Departamento de Anatomia, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Reis
Alice H
AH
Aguiar
Diego P
DP
Lyons
Karen M
KM
Abreu
José G
JG
D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation; D055513:Connective Tissue Growth Factor; D015870:Gene Expression; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009805:Odontogenesis / Q000235:genetics*; D011485:Protein Binding; D015398:Signal Transduction / Q000502:physiology*; D051899:Smad2 Protein / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D051900:Smad3 Protein / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D051901:Smad4 Protein / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000032:analysis / Q000235:genetics / Q000378:metabolism*
C526318:CCN2 protein, mouse; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D051901:Smad4 Protein; C490810:Smad4 protein, mouse; D016212:Transforming Growth Factor beta; D055513:Connective Tissue Growth Factor