title: Fluid shear stress inhibits TNFalpha-induced osteocyte apoptosis.
abstract: Bone tissue can adapt to orthodontic load. Mechanosensing in bone is primarily a task for the osteocytes, which translate the canalicular flow resulting from bone loading into osteoclast and osteoblast recruiting signals. Apoptotic osteocytes attract osteoclasts, and inhibition of osteocyte apoptosis can therefore affect bone remodeling. Since TNF-alpha is a pro-inflammatory cytokine with apoptotic potency, and elevated levels are found in the gingival sulcus during orthodontic tooth movement, we investigated if mechanical loading by pulsating fluid flow affects TNF-alpha-induced apoptosis in chicken osteocytes, osteoblasts, and periosteal fibroblasts. During fluid stasis, TNF-alpha increased apoptosis by more than two-fold in both osteocytes and osteoblasts, but not in periosteal fibroblasts. One-hour pulsating fluid flow (0.70 +/- 0.30 Pa, 5 Hz) inhibited (-25%) TNF-alpha-induced apoptosis in osteocytes, but not in osteoblasts or periosteal fibroblasts, suggesting a key regulatory role for osteocyte apoptosis in bone remodeling after the application of an orthodontic load.
authors.affiliation: Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA)-Universiteit van Amsterdam and Vrije Universiteit, Van der Boechorststraat 7, NL-1081 BT Amsterdam, The Netherlands.
authors.forename: S D
authors.initials: SD
authors.lastname: Tan
authors.forename: A M
authors.initials: AM
authors.lastname: Kuijpers-Jagtman
authors.forename: C M
authors.initials: CM
authors.lastname: Semeins
authors.forename: A L J J
authors.initials: AL
authors.lastname: Bronckers
authors.forename: J C
authors.initials: JC
authors.lastname: Maltha
authors.forename: J W
authors.initials: JW
authors.lastname: Von den Hoff
authors.forename: V
authors.initials: V
authors.lastname: Everts
authors.forename: J
authors.initials: J
authors.lastname: Klein-Nulend
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D016723:Bone Remodeling / Q000502:physiology*; D002478:Cells, Cultured; D002642:Chick Embryo; D015536:Down-Regulation; D045604:Extracellular Fluid / Q000502:physiology; D005347:Fibroblasts / Q000502:physiology; D010006:Osteoblasts / Q000502:physiology*; D010011:Osteocytes / Q000502:physiology*; D010521:Periosteum / Q000166:cytology / Q000502:physiology; D011673:Pulsatile Flow; D033081:Shear Strength; D012886:Skull / Q000166:cytology; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*; D016474:Weight-Bearing
chemical_list: D014409:Tumor Necrosis Factor-alpha