title: Ultrasound Stimulation of Different Dental Stem Cell Populations: Role of Mitogen-activated Protein Kinase Signaling.
abstract: BACKGROUND
  Mesenchymal stem cells (MSCs) from dental tissues may respond to low-intensity pulsed ultrasound (LIPUS) treatment, potentially providing a therapeutic approach to promoting dental tissue regeneration. This work aimed to compare LIPUS effects on the proliferation and MAPK signaling in MSCs from rodent dental pulp stem cells (DPSCs) compared with MSCs from periodontal ligament stem cells (PDLSCs) and bone marrow stem cells (BMSCs).
  
  
  METHODS
  Isolated MSCs were treated with 1-MHz LIPUS at an intensity of 250 or 750 mW/cm2 for 5 or 20 minutes. Cell proliferation was evaluated by 5-bromo-2-deoxyuridine (BrdU) staining after 24 hours of culture following a single LIPUS treatment. Specific ELISAs were used to determine the total and activated p38, ERK1/2, and JNK MAPK signaling proteins up to 4 hours after treatment. Selective MAPK inhibitors PD98059 (ERK1/2), SB203580 (p38), and SP600125 (JNK) were used to determine the role of activation of the particular MAPK pathways.
  
  
  RESULTS
  The proliferation of all MSC types was significantly increased after LIPUS treatment. LIPUS at a 750-mW/cm2 dose induced the greatest effects on DPSCs. BMSC proliferation was stimulated in equal measures by both intensities, whereas 250 mW/cm2 LIPUS exposure exerted maximum effects on PDLSCs. ERK1/2 was activated immediately in DPSCs after treatment. Concomitantly, DPSC proliferation was specifically modulated by ERK1/2 inhibition, whereas p38 and JNK inhibition exerted no effects. In BMSCs, JNK MAPK signaling was LIPUS activated, and the increase in proliferation was blocked by specific inhibition of the JNK pathway. In PDLSCs, JNK MAPK signaling was activated immediately after LIPUS, whereas p-p38 MAPK increased significantly in these cells 4 hours after exposure. Correspondingly, JNK and p38 inhibition modulated LIPUS-stimulated PDLSC proliferation.
  
  
  CONCLUSIONS
  LIPUS promoted MSC proliferation in an intensity and cell-specific dependent manner via activation of distinct MAPK pathways.
authors.affiliation: School of Dentistry, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Qianhua
authors.initials: Q
authors.lastname: Gao
authors.affiliation: School of Dentistry, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom.
authors.forename: A Damien
authors.initials: AD
authors.lastname: Walmsley
authors.affiliation: School of Dentistry, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Cooper
authors.affiliation: School of Dentistry, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom. Electronic address: b.a.scheven@bham.ac.uk.
authors.forename: Ben A
authors.initials: BA
authors.lastname: Scheven
mesh_terms: D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation / Q000528:radiation effects; D049109:Cell Proliferation / Q000528:radiation effects; D002478:Cells, Cultured; D003782:Dental Pulp / Q000166:cytology* / Q000528:radiation effects*; D020935:MAP Kinase Signaling System / Q000528:radiation effects*; D008297:Male; D059630:Mesenchymal Stem Cells / Q000201:enzymology / Q000528:radiation effects; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010513:Periodontal Ligament / Q000166:cytology / Q000528:radiation effects; D051381:Rats; D017208:Rats, Wistar; D012038:Regeneration / Q000528:radiation effects; D013234:Stem Cells / Q000201:enzymology* / Q000528:radiation effects*; D014464:Ultrasonic Therapy / Q000379:methods*; D000069453:Ultrasonic Waves
chemical_list: D020928:Mitogen-Activated Protein Kinases
keywords: Bone marrow mesenchymal stem cells; cell proliferation; dental pulp stem cells; dental tissue regeneration; low-intensity pulsed ultrasound; mesenchymal stem cells; mitogen-activated protein kinase signaling; periodontal ligament–derived stem cells; ultrasound