MEPE is downregulated as dental pulp stem cells differentiate.
Previous studies on dental pulp cell culture have described heterogenous mixtures of cells that differentiate into odontoblasts and form mineralized dentin.


OBJECTIVE
The aim of this study was to characterize the matrix extracellular phosphoglycoprotein (MEPE) expression by dental pulp stem cells (DPSC), related to cell differentiation.


METHODS
DPSC differentiation to form mineralized nodules was characterized by Alizarin red staining and micro-Raman spectroscopy. Osteogenesis SuperArray analysis was used to broadly screen for osteogenesis-related genes altered by DPSC differentiation. Relative levels of expression of MEPE and DSP were determined by semiquantitative RT-PCR and Western blot.


RESULTS
Mineral analysis showed that as DPSC differentiated, they formed a carbonated hydroxyapatite mineral. Differentiation was initially marked by upregulation by Runx2, TGFbeta-related genes, EGFR and genes involved in collagen metabolism. ALP activity first increased, as DPSCs reached confluence but later decreased when cells further differentiated three weeks after confluence. MEPE was the only marker that was downregulated as DPSCs differentiated.


CONCLUSIONS
DPSC differentiation can be characterized by downregulation of MEPE as other markers of DPSC differentiation, such as DSP, are upregulated. Expression of MEPE related to DSP and can be used to monitor DPSC as they are used for studies of odontoblast differentiation, tissue engineering or vital pulp therapy. The downregulation of MEPE as DPSC differentiate, suggests that MEPE is an inhibitor of mineralization.
Liu
He
H
University of California, San Francisco, Growth and Development, 521 Parnassus Avenue, Rm C734, Box 0640, San Francisco, CA 94143-0640, USA.
Li
Wu
W
Shi
Songtao
S
Habelitz
Stefan
S
Gao
Cen
C
Denbesten
Pamela
P
D015415:Biomarkers / Q000032:analysis; D015153:Blotting, Western / Q000379:methods; D002454:Cell Differentiation; D002478:Cells, Cultured; D003782:Dental Pulp / Q000166:cytology* / Q000378:metabolism; D003810:Dentinogenesis / Q000502:physiology*; D015536:Down-Regulation; D016326:Extracellular Matrix Proteins / Q000032:analysis / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D006023:Glycoproteins / Q000032:analysis / Q000235:genetics*; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D010750:Phosphoproteins / Q000032:analysis / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism
D015415:Biomarkers; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; C486579:MEPE protein, human; D010750:Phosphoproteins