The role of oxygen in blastema formation and skeletal regeneration

描述(由申请人提供)：在美国，每200人中就有一人会被截肢，预计这一数字在未来40年内将翻一番。截肢对职业成就、个人生产力和个人独立性的持久影响远远超出了最初的创伤。虽然人类完全的肢体再生有一天可能成为终极治疗方法，但协调控制骨再生的能力将减少异位骨刺带来的疼痛，并为假体提供更好的适应，从而产生更好的 近期的生活。在啮齿动物、猴子和人类的末端指骨内截断指尖，可以从胚泡中近乎完美地再生，这在成年和新生小鼠中都有很好的特征。然而，目前尚不清楚为什么更多的近端手指截肢或四肢内截肢未能产生同样的再生结果。这项工作的长期目标是了解氧气对再生的影响，以便在缺乏氧气的情况下，可以利用这些机制来赋予再生能力。这项研究的目的是通过操纵指尖内的氧气来改变再生，从而深入了解氧气在再生过程中的作用。我们的中心假设是 两相氧气反应促进了再生过程。我们的假说源于再生模型的双相性，以及氧在伤口愈合过程中的已知影响。高度增殖、未分化的胚泡在低氧环境中形成。暴露在氧气压力升高的环境中会启动胚泡分化为骨骼，这支持了驱动再生过程的双相氧反应的观点。这项研究的基本原理是，了解促进骨再生的氧气梯度不仅可以更好地了解再生过程，还将为治疗干预提供机会。中心假设将通过两个具体的目标来检验：1)确定氧气对胚泡形成和维持的影响。基于无血管胚泡的证据，以及低氧维持成骨细胞前体细胞的多能性和增殖率，我们的工作假设是，最初的低氧事件对于促进胚泡结构的建立至关重要，因为过量的氧气可以改变再生的速度。我们假设，当再生的指头已经缺氧时，刺激缺氧级联反应，而当指头活跃地矿化骨骼时，增加氧分压将对再生过程的速度产生净相加效应。 这些目标的完成将为再生过程提供在氧气环境下形成新骨的预测能力，并提供明确的干预点来操纵再生结果。这项工作的研究将导致对氧气在骨再生中的作用有明确的机制理解，并确定提高再生能力的治疗靶点。 公共卫生相关性：截肢对一个人的职业选择、个人生产力和独立性有深远的影响。在美国，每200人中就有一人是截肢者，由于继发性血管疾病截肢的增加，这一数字预计在未来40年内将翻一番。伤口愈合被认为取决于伤口部位适当的氧气水平，我们的长期目标是了解氧气在肢体再生中的作用，以便将这些发现作为优化截肢者治疗的关键一步。

DESCRIPTION (provided by applicant): One out of every 200 people in the U.S. will suffer an amputation, and this number is expected to double in the next 40 years. Amputation has protracted effects on vocational outcome, individual productivity, and personal independence far beyond the initial trauma. While complete limb regeneration in humans may someday become the ultimate therapy, the ability to coordinately control bone regeneration would reduce pain from ectopic bone spurs, and provide a better fit for prosthetics, resulting in a better quality of life in the near term. Amputation of the digit tip within the terminal phalangeal bone of rodents, monkeys, and humans results in near-perfect regeneration from the blastema, which has been well characterized in both adult and neonatal mice. However, it remains unclear why more proximal digit amputations or amputations within limbs, fail to produce the same regenerative result. The long term goal of this work is to understand the influence of oxygen on regeneration, so that these mechanisms can be exploited to confer regenerative capacity where it is lacking. The objective of this study is to gain insight into the role of oxygen in the regenerative process by manipulating oxygen within the digit tip to alter regeneration. Our central hypothesis is that a biphasic oxygen response facilitates the regenerative process. Our hypothesis stems from the biphasic nature of the regenerative models, and oxygen's known influence in the process of wound healing. The highly proliferative, undifferentiated blastema forms in a hypoxic environment. Exposure to increased oxygen tension initiates the differentiation of the blastema into bone, supporting the idea of a biphasic oxygen response that drives the regenerative process. The rationale for this study is that understanding the oxygen gradients that promote bone regeneration will not only provide a better understanding of the regenerative process, but will also provides opportunities for therapeutic intervention. The central hypothesis will be teste by two specific aims: 1) Determine the influence of oxygen on the formation and maintenance of the blastema. Based on evidence of an avascular blastema, and that hypoxia maintains the multipotency and proliferation rate of osteoblast precursor cells, our working hypothesis is that an initial hypoxic event is critical for promoting the blastema structure 2) Establish to what extet oxygen modifies the rate of regeneration. We hypothesize that stimulating hypoxic cascades when the regenerating digit is already hypoxic, and increasing oxygen tension when the digit is actively mineralizing bone will have a net additive effect on the rate of the regenerative process. Completion of these aims will provide predictive capacity for the regenerative process to form new bone in the context of oxygen, and provide defined points of intervention to manipulate regenerative outcome. Research enabled by this work will lead to a defined mechanistic understanding of oxygen's role in bone regeneration and identify therapeutic targets to enhance regenerative capacity. PUBLIC HEALTH RELEVANCE: Limb amputation has a profound impact on a person's vocational options, individual productivity, and independence. One out of every 200 people in the United States is an amputee, and this number is expected to double in the next 40 years due to an increase in amputations secondary to vascular disease. Wound healing is thought to be contingent upon appropriate oxygen levels at the wound site, and our long-term goal is to understand oxygen's role in limb regeneration in order to apply the findings as a critical step towards optimizing treatment for amputees.