title: P16/p53 expression and telomerase activity in immortalized human dental pulp cells.
abstract: BACKGROUND
  Residing within human dental pulp are cells of an ectomesenchymal origin which have the potential to differentiate into odontoblast-like cells. These cells have a limited growth potential owing to the effects of cell senescence. This study examines the effects of immortalizing odontoblast-like cells on cell proliferation and mineralization by comparing transformed dental pulp stem cells (tDPSCs) and non-transformed dental pulp stem cells (nDPSCs).
  
  
  RESULTS
  With the exogenous expression of hTERT, tDPSCs maintained a continued expression of odontogenic markers for cell proliferation and mineralization (ALP, COL-1, DMP-1, DSPP, OCN amd OPN)as did nDPScs. Oncoprotein expression was seen in both groups except for a noted absence of p16 in the tDPSCs. nDPSCs also showed lower levels of total ALP and DNA activity in comparison to tDPSCs when assayed as well as low telomerase activity readings.
  
  
  METHODS
  Using a retroviral vector, exogenous human telomerase reverse transcriptase (hTERT) was expressed in tDPSCs. Both cell groups were cultured and their telomerase activities is determined using a telomerase quantification assay. Also examined were the expression of genes involved in proliferation and mineralization such as human alkaline phosphatase (ALP), β-actin, collagen 1 (col-1), core binding factor (cbfa-1), dentin matrix protein (DMP-1), dentin sialophosphoprotein (DSPP), GAPDH, hTERT, osteocalcin (OCN), osteopontin (OPN) as well as oncoproteins involved in senescence (p16, p21 and p53) using RT-PCR. DNA and alkaline phosphatase activity was assayed in both cell groups.
  
  
  CONCLUSIONS
  These results indicate maintainance of odontoblast-like differentiation characteristics after retroviral transformation with hTERT and suggest a possible link with a reduced p16 expression.
authors: Biomaterials and Biomimetics, King's College London, London, UK.
authors: Obi
authors: O
authors: Egbuniwe
authors: Bernadine D
authors: BD
authors: Idowu
authors: Juan M
authors: JM
authors: Funes
authors: Andrew D
authors: AD
authors: Grant
authors: Tara
authors: T
authors: Renton
authors: Lucy
authors: L
authors: Di Silvio
mesh_terms: D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D002454:Cell Differentiation; D049109:Cell Proliferation; D003124:Colorimetry; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis / Q000378:metabolism*; D003599:Cytoskeleton / Q000648:ultrastructure; D003782:Dental Pulp / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D039904:Pluripotent Stem Cells / Q000166:cytology / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019098:Telomerase / Q000378:metabolism* / Q000494:pharmacology; D014161:Transduction, Genetic; D016159:Tumor Suppressor Protein p53 / Q000032:analysis / Q000378:metabolism*; D001616:beta-Galactosidase / Q000032:analysis
chemical_list: D015415:Biomarkers; D019941:Cyclin-Dependent Kinase Inhibitor p16; D016159:Tumor Suppressor Protein p53; D019098:Telomerase; D001616:beta-Galactosidase