title: Epithelial cell rests of Malassez modulate cell proliferation, differentiation and apoptosis via gap junctional communication under mechanical stretching in vitro.
abstract: Epithelial cell rests of Malassez (ERM) are involved in the maintenance and homeostasis of the periodontal ligament. The objective of this study was to investigate the effect of mechanical stretching on cell growth, cell death and differentiation in the ERM. Cultured porcine ERM were stretched for 24 hr in cycles of 18% elongation for 1 sec followed by 1 sec relaxation. The numbers of cells and TUNEL-positive cells were then counted. The expression of mRNAs encoding gap junction protein α1 (Gja1), ameloblastin, bone morphogenetic protein 2 (BMP2), bone morphogenetic protein 4 (BMP4) and noggin were evaluated using quantitative real-time PCR. The number of cells in the stretching group was approximately 1.3-fold higher than that in the non-stretching controls at 24 hr (p<0.01). Apoptotic cells ranged from 1.9-2.5% in the stretching group at 24 hr, but were only 0.6% in the control group (p<0.01). The expression of Gja1, ameloblastin and noggin mRNAs in the stretching group was decreased at 24 hr compared with in the non-stretching group (p<0.01), whereas the expression of BMP2 and BMP4 mRNAs in the stretching group was significantly higher than that in the control group (p<0.01). Incorporation of 18 α-glycyrrhetinic acid (18GA, a gap junction inhibitor) promoted proliferation and apoptosis and confirmed both the increase of BMP2 and BMP4 and the decline of Gja1, ameloblastin and noggin in ERM. Thus, the ERM modulate cell proliferation and apoptosis, and inhibit differentiation by reducing expression of Gja1 under mechanical stretching.
authors.affiliation: Department of Clinical Pathophysiology, Tokyo Dental College, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Haku
authors.forename: Takashi
authors.initials: T
authors.lastname: Muramatsu
authors.forename: Arisa
authors.initials: A
authors.lastname: Hara
authors.forename: Akira
authors.initials: A
authors.lastname: Kikuchi
authors.forename: Sadamitsu
authors.initials: S
authors.lastname: Hashimoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Inoue
authors.forename: Masaki
authors.initials: M
authors.lastname: Shimono
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D055396:Bone Morphogenetic Protein 2 / Q000235:genetics / Q000378:metabolism; D055415:Bone Morphogenetic Protein 4 / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology*; D049109:Cell Proliferation; D002478:Cells, Cultured; D003799:Dental Stress Analysis; D004847:Epithelial Cells / Q000378:metabolism*; D017629:Gap Junctions / Q000378:metabolism*; D010513:Periodontal Ligament / Q000166:cytology* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D013552:Swine; D000099176:Noggin Protein
chemical_list: D055396:Bone Morphogenetic Protein 2; D055415:Bone Morphogenetic Protein 4; D002352:Carrier Proteins; D012333:RNA, Messenger; D000099176:Noggin Protein