SPARC controls transglutaminase-mediated collagen I cross-links in periodontal disease

项目概要/摘要 胶原纤维跨越牙周膜（PDL）连接牙齿的骨窝编织 穿过每颗牙齿的牙骨质并进入牙槽骨。I型胶原蛋白是主要的结构性胶原蛋白， PDL的组成部分。细胞外基质（ECM）周转率高是PDL组织的特征。 在美国，牙周病（PD）困扰着大约50%的人口。PD标记为 牙周组织的慢性炎症导致牙周膜降解、牙槽骨丢失， 损失目前还没有公认的方法来再生这种胶原性PDL组织。因此PDL 为研究胶原蛋白加工和组装的机制提供了良好的组织环境， 临床相关的炎症状态。胶原蛋白结合蛋白，已被鉴定为一种 胶原ECM沉积的关键因素。我们报道了SPARC基因敲除小鼠的总 与野生型（WT）PDL相比，PDL中的胶原、更薄的胶原纤维和降低的机械强度。一 ECM中不溶性胶原的结合和稳定的关键因素是通过胶原介导的 交联转氨酶（TG）是一个已知参与胶原蛋白合成的细胞外蛋白家族 体外和体内的交联活性。以前的数据表明，甘油三酯作为一个关键的调节剂， 稳态PDL中的胶原I。体内TG活性的抑制被证明可以逆转SPARC依赖性 胶原体积分数和稳态PDL的机械强度降低。我们的数据预测， 通过介导ECM中的底物特异性来调节TG活性，然而， 连接影响胶原结构和修复期间和之后的炎症损伤是未知的。我们 假设组织TG（TG 2）活性响应于损伤而增加会减少胶原纤维 含量和机械强度，以及通过以下任一方式操纵TG 2活性 表达或药物干预将改善胶原蛋白沉积和修复， PD模型我们将通过以下具体目标来研究我们的假设：1。使用临床 PD的相关鼠模型，证明TG 2活性在患有PD的WT小鼠中增加，并且进一步增强 在没有人的情况下，2。证明愈合PDL的胶原蛋白组装和机械强度 降低TG活性，和3.证明成纤维细胞中表达缺失可驱动 PD中胶原I的TG依赖性交联增加。该项目将确定联合国在 在炎症性PDL损伤期间和之后调节TG 2介导的胶原交联。培训 这里提出的计划将测试上述假设，并准备申请人作为一个成功的职业生涯， 学术科学家

Project Summary/Abstract The collagen fibers that span the periodontal ligament (PDL) connect teeth to the bone socket by weaving through the cementum of each tooth as well as into the alveolar bone. Collagen type I is the main structural component of PDL. High rates of extracellular matrix (ECM) turnover are characteristic of PDL tissue. Periodontal disease (PD) afflicts approximately 50% of the population in the United States. PD is marked by chronic inflammation of the periodontium leading to PDL degradation, alveolar bone loss, and eventual tooth loss. There are currently no accepted methodologies to regenerate this collagenous PDL tissue. Thus PDL provides an excellent tissue milieu for investigating mechanisms of collagen processing and assembly during inflammatory states that are clinically relevant. SPARC, a collagen-binding protein, has been identified as a key factor in collagen ECM deposition. We reported that SPARC-null mice have significantly less total collagen, thinner collagen fibers, and reduced mechanical strength in PDL compared to wild type (WT) PDL. A key factor in incorporation and stabilization of insoluble collagen within the ECM is mediated through collagen crosslinking. Transglutaminases (TGs) are a family of extracellular proteins known to participate in collagen cross-linking activity in vitro and in vivo. Previous data implicate SPARC as a critical regulator of TG activity on collagen I in homeostatic PDL. Inhibition of TG activity in vivo was shown to reverse SPARC-dependent decreases in collagen volume fraction and mechanical strength of homeostatic PDL. Our data predicts SPARC regulates TG activity by mediating substrate specificity in the ECM, however, the mechanisms by which cross- links influence collagen architecture and repair during and following inflammatory injury is unknown. We hypothesize that increases in tissue TG (TG2) activity in response to injury diminishes collagen fiber content and mechanical strength in the PDL and that manipulation of TG2 activity through either expression of SPARC or pharmacological intervention will improve collagen deposition and repair in a model of PD. We will investigate our hypothesis through the following Specific Aims: 1. Using a clinically relevant murine model of PD, demonstrate TG2 activity is increased in WT mice with PD and further enhanced in the absence of SPARC, 2. Demonstrate that collagen assembly and mechanical strength of healing PDL is decreased by increased TG activity, and 3. Demonstrate that loss of SPARC expression in fibroblasts drives increased TG-dependent cross-linking of collagen I in PD. This project will determine the role of SPARC in the regulation of TG2-mediated collagen cross-links during and following inflammatory PDL injury. The training plan proposed here will test the above hypothesis and prepare the applicant for a successful career as an academic scientist.