Load-mediated Adaptation of the Bone-PDL-Tooth Complex in Vertebrates

描述（由申请人提供）：本研究的生物工程方面源于沃尔夫定律，该定律解释了由于器官水平的机械负荷而导致的骨适应。在组织和细胞水平，局部应变触发机械生物学事件，并负责维持均匀的功能PDL空间。然而，均匀的PDL空间可以向不均匀的PDL空间移动，这是由于PDL-骨和PDL-牙骨质界面处的应变的畸变（作为改变的机械生物学的结果）。我们将测试细胞和组织水平的反应，这些反应可能导致PDL空间的增加或减少，以及功能变化导致的伴随梯度。我们将研究：目的1）在原位骨表面， 牙齿最初是一致的，并且随着机械载荷的施加，可以在骨-牙齿复合体内引起局部压缩和拉伸应变。PDL空间的变化和产生的应变将使用耦合到微型X射线计算机断层扫描（<$-XCT）的加载装置进行评价，然后对空载和负载条件下拍摄的虚拟切片进行数字图像相关（DIC）;目的2）在体内，机械生物学活性的压缩和拉伸部位通过基因和基质蛋白的表达促进生化变化，引起骨和牙骨质的再吸收和形成，导致PDL空间变宽或变窄。将通过使用基于荧光的免疫组织化学绘制促进张力位点处的矿物质形成、压缩位点处的再吸收以及负责维持组织和界面完整性的机械敏感基因和蛋白质表达的时空结果;目的3）在目的2中鉴定的生物化学改变的区域引起骨、牙骨质，PDL（例如，拉伸应变诱导骨形成）。该目的包括绘制PDL-骨和PDL-牙骨质界面的梯度变化。将使用最先进的高分辨率显微镜和光谱设备绘制湿PDL-骨、PDL-牙骨质、牙骨质、骨和PDL的局部结构、化学成分和机械性能的时空变化;目的4）。在原位的功能上适应的系统具有改变的对机械负载的响应。将评价和比较来自新鲜收获的实验组和对照组（如目标1）的第二磨牙适应复合体的载荷-位移曲线和相关应变场。研究将使用原位加载、<$-XCT和DIC，如目标1所述。健康相关性：拟议的转化研究是基于我们对PDL空间如何适应功能负荷的不完全理解。局部功能适应可能是不利的结果，由于牙根和/或骨吸收或形成导致PDL间隙加宽（牙齿松动）或变窄（关节强直），牙齿运动范围增加或减少。当复合体受到植入物和/或牙周炎、正常或治疗负荷（正畸矫正器）随后损害功能时，这种适应的部位可以充当诱导正反馈的局部应力点。

DESCRIPTION (provided by applicant): The bioengineering aspect of this research originates from Wolff's law which explains bone adaptation due to mechanical loads at an organ-level. At a tissue- and a cell-level, local strains trigger mechanobiological events and are responsible for maintaining a uniform functional PDL-space. However, a uniform PDL-space can shift toward a nonuniform PDL-space due to aberrations in strains at the PDL-bone and PDL-cementum interfaces as a result of altered mechanobiology. We wil test cell- and tissue-level responses that could cause an increase or decrease in PDL-space and the accompanying gradients that result from a change in function. We will investigate: Aim 1) that in situ the surfaces of bone and tooth are originally conforming and with application of mechanical load can induce localized compressive and tensile strains within the bone-tooth complex. Changes in PDL-space and resulting strains will be evaluated using a loading device coupled to a Micro X-ray computed tomography (¿-XCT) followed by digital image correlation (DIC) of virtual sections taken at no load and loaded conditions; Aim 2) that in vivo the mechanobiologically active compression and tension sites promote biochemical changes through expression of genes and matrix proteins, causing resorption and formation of bone and cementum resulting in a widened or a narrowed PDL-space. The spatiotemporal outcomes of mechanosensitive genes and protein expressions promoting mineral formation at the tension sites, resorption at the compression sites, and responsible for maintaining tissue and interface integrity will be mapped by using fluorescence based immunohistochemistry; Aim 3) that biochemically altered regions identified in Aim 2 cause measurable changes in structure, chemical composition and mechanical properties of bone, cementum, PDL (e.g. tensile strains induce bone formation). This aim includes mapping the shifts in gradients of the PDL-bone and PDL-cementum interfaces. Spatiotemporal changes in local structure, chemical composition and mechanical properties of wet PDL-bone, PDL-cementum, cementum, bone, and PDL using state-of-the-art high resolution microscopy and spectroscopy equipment will be mapped; Aim 4). the functionally adapted systems in situ have an altered response to mechanical loads. Load-displacement curves and correlating strains fields in adapted complexes of 2nd molar from freshly harvested experimental groups and controls (as in Aim 1) will be evaluated and compared. Studies will use in situ loading, ¿-XCT, and DIC as in Aim 1. HEALTH RELEVANCE: The proposed translational research is based on our incomplete understanding of how PDL-space adapts to functional loads. Local functional adaptations can be unfavorable outcomes with an increased or a decreased range of tooth motion due to root and/or bone resorption or formation resulting in a widened (tooth loosening) or narrowed PDL-space (ankylosis). Such adapted sites could act as the local stress points inducing positive feedback when the complex is subjected to implants and/or periodontitis, normal or therapeutic loads (orthodontic braces) subsequently impairing function.