Understanding revascularization and repair of cranial bone grafts via intravital imaging

血运重建是植骨愈合和修复的关键决定因素。自体移植是 大大优于同种异体骨移植和人工骨移植，这在很大程度上是因为自体移植可以 迅速血运重建并形成新骨，而同种异体骨不能。同时进行血运重建 骨组织的含量越来越被认为是修复和重建的关键因素，我们的 对骨移植中的骨移植血管化的了解仅限于 70年代初和80年代初描述的组织学观察。这些描述通常是 受限于对组织学的依赖，这禁止了三维和时空 移植骨的血管化分析。我们最近建立了一块颅骨 窗腔模型，允许高分辨率、四维成像和分析 使用多光子激光扫描显微镜在几个月内修复骨缺损 (MPLSM)。通过将同种异体骨和自体骨移植到该开窗骨缺损模型中， 我们能够跟踪血运重建的过程并展示基本的 活体动物同种异体移植和自体移植的区别。我们目前提案的目标是 是利用这种新的活体成像方法结合转基因动物模型来 更好地了解骨移植的血管形成机制。 根据我们的初步数据和最近关于缺氧诱导因子1的关键作用的文献- α(缺氧诱导因子-1α)在成骨和血管生成的氧传感和偶联中的作用，两 提出了互补的目标。目标1将研究HIF-1通路在 HIF-1缺陷或过度活化活骨移植的血运重建和修复 同种异体移植入颅骨缺损室模型。目标2将确定 HIF-1信号增强的骨髓间充质干细胞移植对同种异体骨移植血运重建的影响 修理。一种新型的氧传感器，可以定量测量氧分压 同时将在体内建立成骨和血管生成机制。完成度 我们目前的项目将加强我们对移植物愈合和血运重建的了解 进一步提供理论依据和策略，以提高未来以细胞为基础的治疗的有效性 促进骨骼修复和再生。了解低氧的复杂作用及其 骨移植血运重建和骨愈合方面的主要调节因素将进一步帮助 开发可经常纠正有害后果的新型药物制剂 见于同种异体骨移植愈合的修复和疤痕形成。

Revascularization is a key determining factor in bone graft healing and repair. Autografts are vastly superior to allografts and synthetic bone grafts largely due to the fact that autografts can be rapidly revascularized and form new bone whereas allografts cannot. While vascularization of bone tissue has been increasingly recognized as a key factor in repair and reconstruction, our understanding of bone graft vascularization in bone transplantation has been limited to histological observations described in the early 70s and 80s. These descriptions are often restricted by dependency on histology which prohibits three-dimensional and spatiotemporal analyses of vascularization of the grafted bone. We have recently established a cranial bone window chamber model which allows high resolution, four-dimensional imaging and analyses of bone defect healing over a period of months using multiphoton laser scanning microscopy (MPLSM). By transplanting allograft and autograft bone into this windowed bone defect model, we were able to track the revascularization process and demonstrate the fundamental differences between allografts and autografts in living animals. The goal of our current proposal is to utilize this novel intravital imaging approach combined with transgenic animal models to gain a better understanding of the vascularization mechanisms of bone graft transplantation. Based on our preliminary date and recent literature on the key role of hypoxia-inducible factor 1- alpha (HIF-1α) in oxygen sensing and coupling of osteogenesis and angiogenesis, two complementary Aims are proposed. Aim 1 will examine the key role of the HIF-1 pathway in revascularization and repair by transplantation of a HIF-1 deficient or over-activated live bone isograft into a cranial defect window chamber model. Aim 2 will determine the effects of engraftment of MSCs with enhanced HIF-1 signaling on bone allograft revascularization and repair. A novel oxygen sensor, which allows quantitative measurements of oxygen tension simultaneously with osteogenesis and angiogenesis in vivo will be established. The completion of our current project will enhance our knowledge of graft healing and revascularization and further offer rationales and strategies to augment the efficacy of future cell-based therapy aimed at enhancing bone repair and regeneration. Understanding the complex role of hypoxia and its master regulators in bone graft revascularization and bone healing will further aid in the development of novel pharmaceutical agents that can redress the detrimental outcomes often seen in repair and scarring of bone allograft healing.