Ehnert Sabrina, Sreekumar Vrinda, Aspera-Werz Romina H, Sajadian Sahar O, Wintermeyer Elke, Sandmann Gunther H, Bahrs Christian, Hengstler Jan G, Godoy Patricio, Nussler Andreas K
Siegfried Weller Institute for trauma research at the BG Trauma Center, Eberhard Karls Universität Tübingen, Schnarrenbergstr. 95, 72076, Tübingen, Germany.
IfADo-Leibniz Research Centre for Working Environment and Human Factors at the Technical University Dortmund, Ardeystraße 67, Dortmund, Germany.
J Mol Med (Berl). 2017 Jun;95(6):653-663. doi: 10.1007/s00109-017-1526-4. Epub 2017 Mar 7.
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-β effectively 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-β treatment on the expression of specific HDACs and their cellular effects, e.g., microtubule structures (primary cilia) and mechanosensation. Exposure to TGF-β most significantly induced expression of HDAC6 both on gene and protein level. Being most abundant in the cytoplasm HDAC6 effectively deacetylates microtubule structures. Thus, TGF-β-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-β-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-β impairs 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-β-levels (e.g., diabetics), which frequently suffer from delayed fracture healing despite adequate mechanical stimulation.
Exposure to TGF-β induces expression of HDAC6 in human osteoblasts. TGF-β exposed human osteoblasts show less and distorted primary cilia. TGF-β exposed human osteoblasts are less sensitive towards mechanical stimulation. Mechanosensation can be recovered by HDAC6 inhibitor Tubacin in human osteoblasts.
转化生长因子β（TGF-β）因其对细胞生长和分化的多种作用，是骨密度的关键调节因子。最近，我们发现TGF-β通过上调组蛋白去乙酰化酶（HDAC）活性，有效阻断骨形态发生蛋白（BMP）诱导的成骨细胞成熟。本研究旨在探讨重组人TGF-β处理对特定HDAC表达及其细胞效应的影响，如微管结构（初级纤毛）和机械感受。暴露于TGF-β最显著地在基因和蛋白质水平上诱导HDAC6的表达。HDAC6在细胞质中含量最丰富，能有效使微管结构去乙酰化。因此，TGF-β诱导的HDAC6表达导致初级纤毛变形和缩短，以及纤毛细胞数量减少。初级纤毛被描述为可感知机械刺激。因此，对细胞施加流体流动，刺激成骨细胞功能（碱性磷酸酶活性和基质矿化）。尽管处于流体流动条件下，但TGF-β处理的细胞中受损的初级纤毛与成骨功能降低有关。用Tubacin对HDAC6进行化学抑制可恢复初级纤毛的结构和长度。这些细胞显示出改善的成骨功能，尤其是在流体流动条件下。总结我们的结果，TGF-β通过HDAC6介导的初级纤毛扭曲和/或缩短部分损害人成骨细胞成熟。这一知识为TGF-β水平长期升高的创伤患者（如糖尿病患者）开辟了新的治疗选择，这些患者尽管有足够的机械刺激，但经常遭受骨折愈合延迟的困扰。
暴露于TGF-β会诱导人成骨细胞中HDAC6的表达。暴露于TGF-β的人成骨细胞显示初级纤毛较少且变形。暴露于TGF-β的人成骨细胞对机械刺激不太敏感。HDAC6抑制剂Tubacin可恢复人成骨细胞的机械感受。
