Functional domains of bone sialoprotein in dentoalveolar development and healing

摘要： 口腔健康对整体健康和生活质量至关重要，牙齿在咀嚼中的重要性就是例证， 语言，美学，以及最近口腔健康与糖尿病，心脏病， 早产和老年痴呆症牙周病，周围结缔组织的破坏 牙齿是地球上最普遍的疾病之一，影响47%的成年人和70%的成年人， 为65.牙周复合体是由牙骨质和牙槽骨两种硬组织组成的独特关节， 和介入的未矿化的牙周韧带（PDL）。牙周病会导致 牙周组织和牙齿脱落，如果不治疗。牙周再生或修复的治疗方法 目前，组织是不可预测的，部分原因是关于引导牙齿生长的分子的知识存在空白。 和牙周发育。我们的目标是更成功地促进牙周组织修复，再生， 并恢复功能。指导牙骨质和牙槽骨矿化的因素是适当的 牙周发育和功能，并可能在组织修复中发挥重要作用。骨唾液酸蛋白（基因： BSP）是牙骨质和牙槽骨中高度表达的细胞外基质蛋白 阵BSP基于其高度保守的功能结构域具有多种生物学作用 在胶原蛋白结合（疏水N-末端结构域），羟基磷灰石成核（聚谷氨酸序列）， 和RGD-整联蛋白细胞信号传导（C-末端基序）。BSP被证明是重要的骨骼 发育，因为在Ibsp敲除（Ibsp-/-）小鼠中的基因消融导致骨骼表型， 延迟长骨矿化和减少松质骨重建。然而，BSP的消融导致 在牙槽组织中，甚至更显著的影响，其中Ibsp-/-小鼠表现出缺乏牙骨质，严重 牙槽骨矿化不足、牙齿附着破坏、牙周破裂和牙齿脱落。我们 假设BSP指导成骨细胞功能和矿化活性，并在 牙周和牙槽骨修复。我们将在以下三个目标中检验这一假设：目标1： BSP在I型胶原上的结合位置，以确定BSP可能有助于ECM的空间机制 成矿目的2：阐明RGD整合素结合结构域和胶原蛋白的作用机制。 使用新产生的成牙骨质细胞系和具有敲入突变的突变小鼠 使RGD基序失活。目的3：研究BSP促进牙槽骨愈合的效果， 外源性天然大鼠BSP（nBSP），以研究其作为促进牙槽骨修复的治疗剂的用途。 重要的是，获得的见解不仅有助于牙齿周围牙槽骨的再生， 牙科植入物放置，但也将潜在地适用于愈合关键尺寸的骨缺损， 骨折和改善或逆转全身性骨疾病如骨质疏松症。

Abstract: Oral health is vital for overall health and quality of life, as exemplified by the importance of teeth in mastication, speech, and esthetics, and by recent connections made between oral health and diabetes, heart disease, preterm birth, and Alzheimer's disease. Periodontal disease, the breakdown of the connective tissues around the teeth, is one of the most prevalent diseases on earth, affecting 47% of adults and 70% of adults over the age of 65. The periodontal complex is a unique joint composed of two hard tissues, cementum and alveolar bone, and an intervening and unmineralized periodontal ligament (PDL). Periodontal disease leads to destruction of periodontal tissues and tooth loss if left untreated. Therapeutic approaches to regenerate or repair periodontal tissues are unpredictable at present, in part because of gaps in knowledge regarding molecules guiding dental and periodontal development. Our goal is to more successfully promote periodontal tissue repair, regeneration, and return to function. Factors directing cementum and alveolar bone mineralization are key for proper periodontal development and function, and likely play important roles in tissue repair. Bone sialoprotein (gene: Ibsp; protein: BSP) is an extracellular matrix protein highly expressed during cementum and alveolar bone formation. BSP has several putative biological roles based on its highly conserved functional domains involved in collagen binding (hydrophobic N-terminal domain), hydroxyapatite nucleation (polyglutamic acid sequences), and RGD-integrin cell signaling (C-terminal motif). BSP was demonstrated to be important in skeletal development, as genetic ablation in Ibsp knockout (Ibsp-/-) mice resulted in a skeletal phenotype marked by mildly delayed long bone mineralization and reduced trabecular bone remodeling. However, ablation of BSP causes even more dramatic effects in dentoalveolar tissues, where Ibsp-/- mice exhibited lack of cementum, severely hypomineralized alveolar bone, disrupted dental attachment, periodontal breakdown, and tooth loss. We hypothesize that BSP directs osteoblast function and mineralization activities and plays an important role in periodontal and alveolar bone repair. We will test this hypothesis in the following three aims: Aim 1: Define the binding location of BSP on type I collagen to define spatial mechanisms by which BSP may contribute to ECM mineralization. Aim 2: Elucidate the mechanistic roles of the RGD integrin-binding domain and the collagen- binding domain using newly generated cementoblast cell lines and mutant mice with a knock-in mutation inactivating the RGD motif. Aim 3: Investigate the efficacy of BSP to enhance alveolar bone healing using exogenous native rat BSP (nBSP) to investigate its use as a therapeutic in promoting alveolar bone repair. Importantly, insights gained will aid not only in regeneration of alveolar bone surrounding teeth or necessary for dental implant placement, but will also be potentially applicable towards healing critical size bone defects and fractures, and ameliorating or reversing systemic bone disorders such as osteoporosis.