IDENTIFYING ROADBLOCKS TO LIMB REGENERATION

项目摘要(摘要) 人类天生的肢体再生能力极其有限。因受伤或疾病而失去肢体 是一个主要的健康问题。目前约有200万美国人生活在失去肢体的后果中， 这一数字预计将上升，因为糖尿病和其他关键风险因素的患病率增加 影响血管系统的疾病。截肢的后果对病人来说是深远的，而且大多数人必须 依靠假肢，这些假肢并不完美。如果有一天再生医学方法是可行的，那么它可能是可行的 了解如何自然地实现全肢体置换。为了获得这一理解，我们正在 采用了一种名为Axolotl的动物模型，这种动物可以完全再生以下肢体 截肢，即使是成年人。Axolotl的四肢在解剖学上与人类的四肢相似，它们的最初发育 也很相似。因此，它们为复杂的三维肢体如何再生提供了蓝图 截肢后在功能上整合到现有的残肢中。如果要做到这一点，必须解决的关键问题 范式是如何被翻译成人类论坛的是Axolotl如何激活和培养先祖 新的肢体。此外，可能会对抗成功再生的细胞和分子力量 还必须理解，因为这些疾病通常存在于人类患者中，从而防止再生。 未来的研究可能会阐明引导这些事件的分子和细胞力量是否不是 在哺乳动物中被激活，或者它们是否过早终止，或者它们是否被其他 各种因素。方法是首先彻底了解肢体是如何再生的，然后再使用以下方法 为未来可能的治疗方法开发假说的信息。 在这项提案中，我们利用了我们最近的发现，即axolotl可能会在它们的 反复截肢后可再生四肢。这一发现为确定因素提供了一个独特的机会 这可能会限制再生，也可能会与之对抗。我们将检查祖细胞的激活情况 在连续截肢后，以确定这些细胞是否在再生故障中耗尽。我们还将 考虑巨噬细胞和肌成纤维细胞在重复截肢后再生失败中的作用。我们 将测试我们发现的再生限制是否在局部水平上起作用，在肢体本身内，并接近 截肢的地方，或如果他们的行动更有系统，在身体的其他地方。最后，我们将调查 重复截肢后表达失调的两个基因的活性 和眼睛缺失2，这两者都有人类的关联。这项研究将利用这些机会 由我们的新模型提出，希望增加对再生限制的理解 对于患者未来的再生医学方法来说是必不可少的。

PROJECT SUMMARY (ABSTRACT) Humans have exceedingly limited natural limb regenerative abilities. Limb loss due to injury or disease is a major health problem. About two million Americans currently live with the consequences of limb loss, and this number is expected to rise because of increased prevalence of key risk factors such as diabetes and other diseases that affect vasculature. The consequences of amputation are profound for patients and most must rely on prosthetics, which are not perfect. A regenerative medicine approach may one day be feasible if it were understood how total limb replacement can be naturally achieved. To gain this understanding, we are employing an animal model, the axolotl salamander, which can completely regenerate limbs following amputation, even as adults. Axolotl limbs are anatomically similar to human limbs, and their initial development is similar as well. Thus, they offer a blueprint for how a complex, three-dimensional limb can be regrown and functionally integrated into the existing stump following amputation. Key issues that must be resolved if this paradigm is to be translated into the human forum are how axolotls activate and cultivate the progenitors for the new limb. Additionally, the cellular and molecular forces that might antagonize successful regeneration must also be understood as these might normally exist in human patients and thereby prevent regeneration. Future research could elucidate whether the molecular and cellular forces guiding these events are not activated in mammals, or whether they terminate prematurely, or whether they are overtly blocked by other factors. The approach is to first thoroughly understand how limbs do regenerate, and then later use this information to develop hypotheses for future possible therapies. In this proposal, we leverage our recent finding that axolotls can be compromised in their ability to regenerate limbs following repeated amputation. This finding presents a unique opportunity to identify factors that may be limiting in regeneration or may antagonize it. We will examine activation of progenitor cells following successive amputations to determine if these cells are exhausted in regenerative failure. We will also consider the role of macrophages and myofibroblasts in regenerative failure following repeated amputation. We will test if the regenerative limitations we uncovered operate at a local level, within the limb itself and close to the site of amputation, or if they act more systemically, elsewhere in the body. Finally, we will investigate the activities of two genes whose expression becomes dysregulated following repeated amputation, amphiregulin and eyes absent 2, both of which have human correlates. This research will capitalize on the opportunities presented by our new model with the hope that increased understanding of regenerative limitations will be essential for future regenerative medicine approaches in patients.