Sequential expression of endothelial nitric oxide synthase, inducible nitric oxide synthase, and nitrotyrosine in odontoblasts and pulp cells during dentin repair after tooth preparation in rat molars

Yu Feng Mei, Takayoshi Yamaza, Ikiru Atsuta, Atsushi Danjo, Yoshio Yamashita, Mizuho A. Kido, Masaaki Goto, Akifumi Akamine, Teruo Tanaka

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Nitric oxide (NO) stimulates osteoblast differentiation, but whether NO contributes to odontoblast differentiation during dentin repair is unknown. By using reverse transcription/polymerase chain reaction and immunostaining, we investigated the gene expression and/or immunolocalization of endothelial NO synthase (eNOS), inducible NOS (iNOS), and nitrotyrosine (a biomarker for NO-derived peroxinitrite), and alkaline phosphatase (ALP) and osteocalcin (early and terminal differentiation markers of odontoblasts, respectively) in dental pulp tissue after rat tooth preparation. At the early stage (1-3 days) post-preparation, markedly increased expression of iNOS and nitrotyrosine was found in odontoblasts and pulp cells beneath the cavity, whereas eNOS expression was significantly decreased. ALP mRNA expression was significantly increased after 1 day but decreased after 3 days, whereas ALP activity was weak in the dentin-pulp interface under the cavity after 1 day but strong after 3 days. Osteocalcin mRNA expression was significantly increased at this stage. At 7 days post-preparation, tertiary dentin was formed under the cavity. All the molecules studied were expressed at control levels in odontoblasts/pulp cells beneath the cavity. These findings show that abundant NO is released from odontoblasts and pulp cells at an early stage after tooth preparation and indicate that, after tooth preparation, the up-regulation of iNOS and nitrotyrosine in odontoblasts is synchronized with increased cellular expression of ALP and osteocalcin. Therefore, the NO synthesized by iNOS after tooth preparation probably participates in regulating odontoblast differentiation during tertiary dentinogenesis.

Original languageEnglish
Pages (from-to)117-127
Number of pages11
JournalCell and tissue research
Issue number1
Publication statusPublished - Apr 1 2007


All Science Journal Classification (ASJC) codes

  • Pathology and Forensic Medicine
  • Histology
  • Cell Biology

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