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Wolff定律，该定律解释了器官水平上由于机械负荷而导致的骨适应。在组织和细胞水平上，局部菌株触发机械生物学事件，并负责维持统一的功能pdl空间。然而，由于力学生物学的改变，由于pdl -骨和pdl -骨质界面的应变畸变，均匀的pdl空间可能会向不均匀的pdl空间转变。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，以及由功能变化引起的伴随梯度。我们将研究：目的1)原位骨表面和

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.