title: Re-oxygenation improves hypoxia-induced pulp cell arrest.
abstract: Dental pulp cells can be exposed to hypoxia during severe inflammation or restorative procedures, though their response to hypoxia is not well-understood. We hypothesized that hypoxia has effects on the growth of pulp cells in vitro. When the cells were exposed to hypoxia for 48 hr, cell growth was suppressed, and cell death was detected by Hoechst staining. Western blot analysis revealed that phosphorylation of retinoblastoma protein was inhibited in cells exposed to hypoxia. Analyses of the molecules involved in retinoblastoma protein phosphorylation revealed that hypoxia suppressed cyclin D2 and activated p21(CIP1/WAF1). Further, hypoxia-exposed pulp cells showed improvement of cell viability, cell-cycle progression, and expression of cyclin D2 with re-oxygenation. These findings indicate that hypoxia-induced cell cycle arrest in pulp cells is reversible, while cyclin D2 may play an essential role in the improvement of cell proliferation with re-oxygenation.
authors.affiliation: Division of Pulp Biology, Operative Dentistry, and Endodontics, Department of Cariology and Periodontology, Science of Oral Functions, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita, Kitakyushu 803-8580, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ueno
authors.forename: C
authors.initials: C
authors.lastname: Kitamura
authors.forename: M
authors.initials: M
authors.lastname: Terashita
authors.forename: T
authors.initials: T
authors.lastname: Nishihara
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D015687:Cell Hypoxia / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D056742:Cyclin D2; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D003782:Dental Pulp / Q000166:cytology* / Q000378:metabolism*; D010100:Oxygen / Q000494:pharmacology; D010766:Phosphorylation; D051381:Rats; D016160:Retinoblastoma Protein / Q000378:metabolism
chemical_list: C486197:Ccnd2 protein, rat; C493958:Cdkn1a protein, rat; D056742:Cyclin D2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016160:Retinoblastoma Protein; D010100:Oxygen