title: TGF-β1impairs mechanosensation of human osteoblasts via HDAC6-mediated shortening and distortion of primary cilia.
abstract: Transforming growth factor β (TGF-β) is a critical regulator of bone density owing to its multiple effects on cell growth and differentiation. Recently, we have shown that TGF-β1effectively blocks bone morphogenetic protein (BMP) induced maturation of osteoblasts by upregulating histone deacetylase (HDAC) activity. The current study aimed at investigating the effect of rhTGF-β1treatment on the expression of specific HDACs and their cellular effects, e.g., microtubule structures (primary cilia) and mechanosensation. Exposure to TGF-β1most significantly induced expression of HDAC6 both on gene and protein level. Being most abundant in the cytoplasm HDAC6 effectively deacetylates microtubule structures. Thus, TGF-β1-induced expression of HDAC6 led to deformation and shortening of primary cilia as well as to reduced numbers of ciliated cells. Primary cilia are described to sense mechanical stimuli. Thus, fluid flow was applied to the cells, which stimulated osteoblast function (AP activity and matrix mineralization). Compromised primary cilia in TGF-β1-treated cells were associated with reduced osteogenic function, despite exposure to fluid flow conditions. Chemical inhibition of HDAC6 with Tubacin restored primary cilium structure and length. These cells showed improved osteogenic function especially under fluid flow conditions. Summarizing our results, TGF-β1impairs human osteoblast maturation partially via HDAC6-mediated distortion and/or shortening of primary cilia. This knowledge opens up new treatment options for trauma patients with chronically elevated TGF-β1-levels (e.g., diabetics), which frequently suffer from delayed fracture healing despite adequate mechanical stimulation.
  
  
  
  Exposure to TGF-β1induces expression of HDAC6 in human osteoblasts. TGF-β1exposed human osteoblasts show less and distorted primary cilia. TGF-β1exposed human osteoblasts are less sensitive towards mechanical stimulation. Mechanosensation can be recovered by HDAC6 inhibitor Tubacin in human osteoblasts.
authors.affiliation: Siegfried Weller Institute for trauma research at the BG Trauma Center, Eberhard Karls Universität Tübingen, Schnarrenbergstr. 95, 72076, Tübingen, Germany. sabrina.ehnert@med.uni-tuebingen.de.
authors.forename: Sabrina
authors.identifier: 0000-0003-4347-1702
authors.initials: S
authors.lastname: Ehnert
authors.affiliation: Siegfried Weller Institute for trauma research at the BG Trauma Center, Eberhard Karls Universität Tübingen, Schnarrenbergstr. 95, 72076, Tübingen, Germany.
authors.forename: Vrinda
authors.initials: V
authors.lastname: Sreekumar
authors.affiliation: Siegfried Weller Institute for trauma research at the BG Trauma Center, Eberhard Karls Universität Tübingen, Schnarrenbergstr. 95, 72076, Tübingen, Germany.
authors.forename: Romina H
authors.initials: RH
authors.lastname: Aspera-Werz
authors.affiliation: Siegfried Weller Institute for trauma research at the BG Trauma Center, Eberhard Karls Universität Tübingen, Schnarrenbergstr. 95, 72076, Tübingen, Germany.
authors.forename: Sahar O
authors.initials: SO
authors.lastname: Sajadian
authors.affiliation: Siegfried Weller Institute for trauma research at the BG Trauma Center, Eberhard Karls Universität Tübingen, Schnarrenbergstr. 95, 72076, Tübingen, Germany.
authors.forename: Elke
authors.initials: E
authors.lastname: Wintermeyer
authors.affiliation: Siegfried Weller Institute for trauma research at the BG Trauma Center, Eberhard Karls Universität Tübingen, Schnarrenbergstr. 95, 72076, Tübingen, Germany.
authors.forename: Gunther H
authors.initials: GH
authors.lastname: Sandmann
authors.affiliation: Siegfried Weller Institute for trauma research at the BG Trauma Center, Eberhard Karls Universität Tübingen, Schnarrenbergstr. 95, 72076, Tübingen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Bahrs
authors.affiliation: IfADo-Leibniz Research Centre for Working Environment and Human Factors at the Technical University Dortmund, Ardeystraße 67, Dortmund, Germany.
authors.forename: Jan G
authors.initials: JG
authors.lastname: Hengstler
authors.affiliation: IfADo-Leibniz Research Centre for Working Environment and Human Factors at the Technical University Dortmund, Ardeystraße 67, Dortmund, Germany.
authors.forename: Patricio
authors.initials: P
authors.lastname: Godoy
authors.affiliation: Siegfried Weller Institute for trauma research at the BG Trauma Center, Eberhard Karls Universität Tübingen, Schnarrenbergstr. 95, 72076, Tübingen, Germany.
authors.forename: Andreas K
authors.initials: AK
authors.lastname: Nussler
mesh_terms: D000368:Aged; D000813:Anilides / Q000494:pharmacology; D002478:Cells, Cultured; D002923:Cilia / Q000187:drug effects / Q000502:physiology*; D005260:Female; D000073864:Histone Deacetylase 6 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D008297:Male; D040542:Mechanotransduction, Cellular; D008875:Middle Aged; D010006:Osteoblasts / Q000502:physiology*; D010012:Osteogenesis; D053773:Transforming Growth Factor beta1 / Q000502:physiology*
chemical_list: D000813:Anilides; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D053773:Transforming Growth Factor beta1; C474316:tubacin; C433811:HDAC6 protein, human; D000073864:Histone Deacetylase 6
keywords: Histone deacetylase 6 (HDAC6); Primary cilia; Primary human osteoblasts (phOBs); Transforming growth factor β (TGF-β)