Mechanical stress promotes odontoblastic differentiation via the heme oxygenase-1 pathway in human dental pulp cell line.
OBJECTIVE
Although heme oxygenase-1 (HO-1) is involved in osteoblastic differentiation, the HO-1- and odontoblastic differentiation-inducing effects of mechanical stress (MS) have not been clarified in human dental pulp cells (HDPCs). In this study, we examined the effects of MS on the odontoblastic differentiation of immortalized HDPCs and on the primary intracellular signaling pathways, including the HO-1 pathway, implicated in this differentiation.


METHODS
A Flexercell strain unit was used to generate cyclic tensile strain in HDPCs. Expressions of mRNAs encoding HO-1 and HDPC differentiation markers, such as osteopontin (OPN), bone sialoprotein (BSP), dentin sialophosphoprotein (DSPP), and dentin matrix-protein-1 (DMP-1), were evaluated using the reverse transcription-polymerase chain reaction. Expression of the NF-E2-related transcription factor 2 (Nrf2) protein was analyzed by Western blotting.


RESULTS
MS significantly increased the expression of HO-1, OPN, BSP, DSPP, and DMP-1 mRNAs in HDPCs. HO-1 silencing and inhibitors of HO-1, p38 MAPK, ERK, phosphoinositide 3-kinase, and nuclear factor-kappaB (NF-kappaB) all attenuated MS-stimulated differentiation. The MS-induced nuclear translocation of Nrf2 was suppressed by inhibitors of PI3K and NF-kappaB.


CONCLUSIONS
Collectively, these results provide the first evidence that MS stimulates odontoblastic differentiation of HDPCs via modulation of the Nrf2-mediated HO-1 pathway.
Lee
Sun-Kyung
SK
Department of Oral and Maxillofacial Pathology, College of Dentistry, Wonkwang University, Iksan, South Korea.
Lee
Chae-Young
CY
Kook
Yoon-Ah
YA
Lee
Suk-Keun
SK
Kim
Eun-Cheol
EC
D015153:Blotting, Western; D002454:Cell Differentiation; D002460:Cell Line; D003782:Dental Pulp / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051547:Heme Oxygenase-1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D009804:Odontoblasts / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical; D014162:Transfection
D004791:Enzyme Inhibitors; D034741:RNA, Small Interfering; D051547:Heme Oxygenase-1