Therapeutic potential of systemic and localized zinc delivery for modulating fracture repair

骨折是每年影响数百万人的常见损伤， 导致行动不便，长期护理，甚至过早死亡。据了解，控制 机械加载可以提高骨折修复的质量和速度，但我们对机械加载的理解， 治疗方法仍然不发达。最近的研究表明，锌可能发挥了重要作用， 骨折修复的进展已知锌可刺激新骨形成，保持骨量， 调节细胞凋亡。重要的是，细胞内锌稳态必须仔细协调，以调节 摄取、排泄和细胞内储存/运输。认为锌可能是机械敏感的; 然而，机械负荷、锌稳态和骨折愈合之间的关系仍然存在， 不清楚该项目将产生关于机械传导之间关系的初步数据， 并建立机械负荷转移和细胞内锌稳态之间的联系， 骨折我们的总体假设是，锌与机械负荷的结合将导致 协同骨愈合反应。在目标1中，我们将扩展我们现有的K25研究，在体内大鼠股骨 截骨术模型，并确定锌输送和负荷转移引起的骨愈合变化。Sprague 道利大鼠将进行股骨截骨和重建。通过胼胝体的机械载荷将是 通过刚性锁定接骨板（0-3%应变，骨折端低载荷）或更柔顺的锁定进行控制 接骨板（10-15%应变，断裂处的高载荷）。动物体内的锌水平将被系统地操纵 （通过饮食）和局部（植入非承重髓内钉）。我们假设 机械负荷和锌递送的组合应用将导致骨的协同改善， 愈合，表现为愈伤组织的更快和更强大的发展。骨愈合的变化将 通过显微CT成像、生物力学测试、组织学和qPCR进行定量。在目标2中，我们将定义 锌的输送、负荷转移、锌的储存/运输和成骨细胞形成之间的因果关系 体外细胞培养模型。在这里，我们将使用细胞培养技术来研究人类的命运， 间充质干细胞我们假设，将富含锌的细胞接种在坚硬光滑的表面上， 改善成骨细胞增殖和上级钙基质形成。这些实验将产生 对细胞接受和响应机械刺激的机制有了新的认识 并为锌增强机械疗法的长期发展提供基础数据。 表征这些关系可能对细胞机械生物学和 开发用于骨再生和修复的机械治疗方法。

Bone fractures are common injuries that impact millions of people each year, and poorly healed fractures cause impaired mobility, long-term nursing care, or even premature death. It is known that controlled mechanical loading can improve the quality and speed of fracture repair, but our understanding of mechano- therapeutics is still underdeveloped. Recent research has indicated that zinc may play a fundamental role in the evolution of fracture repair. Zinc is known to stimulate new bone formation, preserve bone mass, and regulate apoptosis. Importantly, intracellular zinc homeostasis must be carefully coordinated to regulate uptake, excretion, and intracellular storage/trafficking. It is believed that zinc may be mechanosensitive; however, the relationships between mechanical loading, zinc homeostasis, and fracture healing remain unclear. This project will generate preliminary data regarding the relationships between mechanotransduction in regenerative cells and establish links between mechanical load transfer and intracellular Zinc homeostasis in bone fractures. Our global hypothesis is that the combination of zinc with mechanical loading will lead to synergistic bone healing responses. In Aim 1, we will extend our existing K25 study with an in vivo rat femoral osteotomy model and determine changes in bone healing caused by zinc delivery and load transfer. Sprague Dawley rats will undergo femoral osteotomy and reconstruction. Mechanical loads across the callus will be controlled with either rigid locking plates (0-3% strain, low load across fracture) or more compliant locking plates (10-15% strain, high load across fracture). Zinc levels in animals will be manipulated systemically (through diet) and locally (implantation of a non-loadbearing intramedullary nail). We hypothesize that the combinatory application of mechanical loads and zinc delivery will lead to synergistic improvements in bone healing that are demonstrated by faster and more robust development of callus. Changes in bone healing will be quantified with micro-CT imaging, biomechanical testing, histology, and qPCR. In Aim 2, we will define the causal relationships between zinc delivery, load transfer, zinc storage/trafficking, and osteoblast formation in an in vitro cell culture model. Here, we will use cell culture techniques to examine the fate of human mesenchymal stem cells. We hypothesize that Zinc-rich cells plated on stiff, smooth surfaces will elicit improved osteoblastic proliferation and superior calcium matrix formation. These experiments will yield fundamental new understanding into the mechanisms by which cells receive and respond to mechanical stimuli and provide foundational data for long-term development of Zinc-augmented mechano-therapeutics. Characterizing these relationships may have immense implications for cellular mechanobiology and development of mechano-therapeutic approaches for bone regeneration and repair.