Pharmacologic Activation of the Hypoxia Inducible Factor Pathway in Bone Healing

描述（由申请人提供）：牵张成骨是肢体重建的有力工具。然而，经常出现的问题、障碍和并发症使患者和医生难以应用这些方法。在这些问题中，延迟或失败的骨愈合可能特别成问题，需要延长外固定和/或额外的手术。分心的一个关键特征是诱导血管生成。先前的研究表明，缺氧诱导因子（HIF）是对氧合改变反应的关键调节因子和血管生成的促进因子，在牵张成骨过程中被强烈诱导。此外，我们已经证明，在小鼠模型中，骨中HIF激活的增加增加了出生后的骨获得。在本研究中，我们将验证HIF通路激活增加将改变牵张成骨过程中骨愈合的假设。我们将使用药物干预来阻止HIF降解，导致HIF激活增加和影响血管生成的下游靶标激活增加。在目标1中，我们将评估药物在体外增加HIF激活和上调下游靶标的潜力，并选择最有希望进行体内评估。在第二个目标中，这些药物将局部应用于胫骨牵张成骨的小鼠牵张区。我们将从组织学、放射学和生物力学角度检查分散的骨骼。此外，第二组实验组将以超理想的速度进行牵张，这是一种导致延迟或不愈合的操作，以测试HIF激活的增加是否可以加快牵张或导致不愈合。

DESCRIPTION (provided by applicant): Distraction osteogenesis is a powerful tool for limb reconstruction. However, frequent problems, obstacles and complications make application of the methods difficult for patients and physicians. Among these issues, delayed or failed bone healing can be particularly problematic, requiring prolonged external fixation and/or additional procedures. A key feature of distraction is the induction of angiogenesis. Prior studies have shown that hypoxia inducible factor (HIF), a key regulator of the response to altered oxygenation and promoter of angiogenesis, is strongly induced during distraction osteogenesis. Further, we have demonstrated that increased HIF activation in bone in a mouse model increases postnatal bone acquisition. In this proposal, we will test the hypothesis that increased activation of HIF pathway will alter bone healing in distraction osteogenesis. We will use pharmacologic intervention to block HIF degradation, resulting in increased HIF activation and increased activation of downstream targets influencing angiogenesis. In aim 1, we will evaluate pharmacologic agents for potential to increase HIF activation and upregulate downstream targets in vitro, and select the most promising for evaluation in vivo. In the second aim, the agents will be applied locally to the distraction zone in mice undergoing distraction osteogenesis of the tibia. We will examine the distracted bones histologically, radiographically and biomechanically. Also, a second experimental group will undergo distraction at a supraoptimal rate, a maneuver that leads to delayed or non healing, to test whether increased HIF activation can allow faster distraction or lead to healing of non-unions.