Elevated extracellular calcium increases fibroblast growth factor-2 gene and protein expression levels via a cAMP/PKA dependent pathway in cementoblasts

Sousuke Kanaya, Eiji Nemoto, Yukari Ebe, Martha J. Somerman, Hidetoshi Shimauchi

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)

Abstract

Cementoblasts, tooth root lining cells, are responsible for laying down cementum on the root surface, a process that is indispensable for establishing a functional periodontal ligament. Cementoblasts share phenotypical features with osteoblasts. Elevated levels of extracellular Ca2+ have been implicated in osteogenesis by stimulating the proliferation and differentiation of osteoblasts; however, the role of extracellular Ca2+ signaling in cementogenesis has not been examined. Using RT-PCR, we found that elevated levels of extracellular Ca2+ increase fibroblast growth factor (FGF)-2 gene expression with a peak at 6h. Pretreatment with a protein kinase A (PKA) inhibitor, H89, or an adenylate cyclase inhibitor, MDL-12,330A, inhibited Ca2+-stimulated Fgf-2 expression. In contrast, pretreatment with the protein kinase C (PKC) inhibitor GF-109203X or the phospholipase C (PLC) inhibitor U73122 did not affect the expression of Fgf-2 transcripts, suggesting that the increase in Fgf-2 expression was dependent on the PKA but not the PLC/PKC signaling pathway. Treatment with an activator of adenylate cyclase, forskolin, or a cell-permeable analog of cAMP, 8-Br-cAMP, enhanced Ca2+-stimulated Fgf-2 expression, but a single treatment with forskolin or 8-Br-cAMP did not, suggesting that cAMP generation is indispensable but not sufficient for Ca2+-stimulated FGF2 expression. Next, we examined the cation specificity of the putative receptor and showed that treatment with trivalent/divalent inorganic ions, Ca2+, Gd3+, Sr2+, or Al3+, caused a dose-dependent increase in Fgf-2 mRNA levels in a cAMP-dependent fashion, whereas Mg2+ and the organic ions neomycin and spermine had no effect on Fgf-2 gene expression levels. These findings suggest that an extracellular Ca2+-sensing mechanism is present in cementoblasts and its activation leads to FGF-2 stimulation in a cAMP/PKA dependent fashion. Understanding the pathway regulating key genes involved in modulating the regeneration of oral tissues will assist in designing regenerative therapies based on reliable biological principles.

Original languageEnglish
Pages (from-to)564-572
Number of pages9
JournalBone
Volume47
Issue number3
DOIs
Publication statusPublished - 2010 Sep

Keywords

  • CAMP
  • Cementoblast
  • Extracellular calcium
  • FGF-2
  • PKA

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Histology

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