CAREER: Engineering nervous tissue in vitro: Discovering the mechanisms of rapid axon stretch growth.

本提案的研究目标是定义和分析与生物体生长相关的拉伸力如何启动独特的神经生物学机制，以适应轴突的拉伸生长，驱动长神经和白质束的自然快速形成。在一个发育中的胚胎中，轴突通过一个生长锥在看似很远的距离内到达它们的目标。然而，在轴突与它们的目标结合并建立突触连接之后，动物和它们的神经系统继续增长几个数量级。可以想象，扩大体对轴突施加的拉伸力是启动和维持轴突圆筒拉伸生长的机制。一种体外组织工程方法已经被开发出来，以概括有机体发育过程中发生的这种根本不同的快速轴突生长形式。这种新发现的神经系统生长形式，即轴突的极端伸展生长，远远超过了锥体的生长速度，每天至少可以达到10毫米。这些研究绘制了生物力学边界，使整合的轴突束能够快速适应不断升级的拉伸生长速率，产生长度为10厘米甚至更长的大型轴突束。值得注意的是，这些极端的拉伸生长条件也刺激轴突直径的扩张，同时保持正常的细胞骨架超微结构和传递动作电位的能力。令人惊讶的是，很少有研究考察机械拉伸对轴突快速生长潜力的影响。轴突拉伸生长提供了一个新的机会，大大扩展了目前对神经系统生长的理解，具有发现加速再生的新目标的真正潜力，为神经修复提供了一个未开发的方向。该模型的其他科学益处可能是能够设计结构神经组织来研究神经系统疾病的病理或有组织的神经元网络的神经生理行为。各个层次的学生都将参与这个令人兴奋和具有挑战性的机会，探索生物工程和神经科学的新领域。此外，还将为残疾学生提供机会和指导，并为残疾高中生及其大学计划提供鼓励和帮助。

Pfister0747615The research objective of this proposal is to define and analyze how stretching forces, associated with the growth of an organism, initiate unique neurobiological mechanisms to accommodate stretch growth of axons, driving the natural and rapid formation of long nerves and white matter tracts. In a developing embryo, axons navigate via a growth cone over seeming large distances to reach their targets. However, well after axons integrate with their targets and establish synaptic connections, animals and their nervous systems continue to grow several orders of magnitude. It is conceivable that stretching forces, exerted on axons by the enlarging body, serves as the mechanism that initiates and maintains stretch growth of the axon cylinder. An in vitro tissue engineering method has been developed to recapitulate this fundamentally different and rapid form of axonal growth that occurs during an organism's development. Far exceeding the rate of growth cone extension, this new-found form of nervous system growth, extreme axon stretch growth, can reach at least 10mm per day. These investigations mapped out the biomechanical boundaries that allow integrated axon bundles to quickly adapt to escalating stretch-growth rates, producing large axon fascicles 10cm in length and potentially much longer. Remarkably, these extreme stretch growth conditions also stimulate expansion of axon caliber, while maintaining a normal cytoskeletal ultrastructure and the ability to convey action potentials. Surprisingly, few studies have examined the effects of mechanical stretch on the rapid growth potential of axons. Axon stretch growth presents a novel opportunity to greatly expand upon the current understanding of nervous system growth with real potential to discover new targets to accelerate regeneration, offering an unexplored direction in nerve repair. Additional scientific benefits of this model could be the ability to engineer structured nervous tissue to study the pathology of nervous system diseases or the neurophysiological behavior of an organized network of neurons. Students at all levels will be included in this exciting and challenging opportunity to explore new territory in bioengineering and neuroscience. Opportunities and mentoring will also be provided for students with disabilities as well as encouragement and assistance for high school students with disabilities and their college plans.