Bisphosphonate modulates cementoblast behavior in vitro.
BACKGROUND
Cementum formation is deemed to be instrumental for the successful regeneration of periodontal tissues, and thus events and modifiers of cementum formation and mineralization need to be determined. This study aimed to determine whether the bisphosphonate 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) altered the behavior of immortalized cementoblasts (osteocalcin-cementoblasts [OCCM]).


METHODS
OCCM from transgenic mice were exposed to HEBP at concentrations ranging from 0.01 to 10.0 microM. The assays performed included the count of cell number for proliferation, Northern blot analysis for gene expression (up to 10 days for core binding factor alpha-1 [Cbfa1], bone sialoprotein [BSP], osteocalcin [OCN], and osteopontin [OPN], markers for cementoblast/osteoblast maturation/mineralization), von Kossa stain and alizarin red S stain for mineralization, and enzyme assay (p-nitrophenol phosphate cleavage) for alkaline phosphatase (ALP) activity.


RESULTS
Mineral nodule formation was inhibited at the higher doses of HEBP (1.0 and 10.0 microM) only. At early stages (1, 3, and 6 days), gene expression assays revealed only subtle changes in treated cells versus untreated cells, but by day 10, groups treated with lower doses (0.01 and 0.1 microM) were markedly different at the gene expression level. OCN was significantly downregulated (70%) at the lowest dose, with less pronounced effects at higher doses. In concurrence, the master switch gene for osteoblasts, Cbfa1, was also downregulated at the lower doses. Inversely, OPN mRNA was enhanced at the lower doses. ALP activity was not altered by HEBP.


CONCLUSIONS
Bisphosphonate alters cementoblast function in vitro through the regulation of gene expression and mineral formation.
Chun
Yong-Hee P
YH
Department of Periodontics/Prevention/Geriatrics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA. ychun@umich.edu
Foster
Brian L
BL
Lukasavage
Patricia A
PA
Berry
Janice E
JE
Zhao
Ming
M
Tenenbaum
Howard C
HC
Somerman
Martha J
MJ
D000469:Alkaline Phosphatase / Q000032:analysis; D000818:Animals; D015415:Biomarkers / Q000032:analysis; D050071:Bone Density Conservation Agents / Q000494:pharmacology*; D002113:Calcification, Physiologic / Q000502:physiology; D002452:Cell Count; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D025021:Cementogenesis / Q000187:drug effects; D050657:Core Binding Factor alpha Subunits / Q000032:analysis; D003739:Dental Cementum / Q000187:drug effects*; D015536:Down-Regulation; D012968:Etidronic Acid / Q000494:pharmacology*; D058574:Integrin-Binding Sialoprotein; D051379:Mice; D008822:Mice, Transgenic; D015675:Osteocalcin / Q000032:analysis / Q000235:genetics; D053495:Osteopontin; D010750:Phosphoproteins / Q000032:analysis; D012795:Sialoglycoproteins / Q000032:analysis
D015415:Biomarkers; D050071:Bone Density Conservation Agents; D050657:Core Binding Factor alpha Subunits; C546872:Ibsp protein, mouse; D058574:Integrin-Binding Sialoprotein; D010750:Phosphoproteins; D012795:Sialoglycoproteins; C506896:Spp1 protein, mouse; C406688:core binding factor alpha; D015675:Osteocalcin; D053495:Osteopontin; D000469:Alkaline Phosphatase; D012968:Etidronic Acid