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

Pfister 0747615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，从而驱动长神经和白色物质束的自然和快速形成。在发育中的胚胎中，轴突通过生长锥在看似很长的距离内导航，以到达它们的目标。然而，在轴突与其目标整合并建立突触连接之后，动物及其神经系统继续增长几个数量级。可以想象的是，由扩大体施加在轴突上的拉伸力用作启动和维持轴突圆柱体的拉伸生长的机制。已经开发了一种体外组织工程方法来重现这种在生物体发育期间发生的根本不同且快速的轴突生长形式。远远超过生长锥延伸的速度，这种新发现的神经系统生长形式，极端轴突拉伸生长，每天至少可以达到10毫米。这些研究绘制出了生物力学边界，允许整合的轴突束快速适应不断升级的拉伸生长速率，产生10厘米长的大轴突束，可能更长。值得注意的是，这些极端的拉伸生长条件也刺激轴突口径的扩张，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，很少有研究探讨了机械拉伸对轴突快速生长潜力的影响。轴突伸展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，具有真实的潜力，可以发现新的靶点来加速再生，为神经修复提供了一个未探索的方向。该模型的其他科学益处可能是能够设计结构化神经组织，以研究神经系统疾病的病理学或有组织神经元网络的神经生理学行为。所有级别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。还将为残疾学生提供机会和指导，并鼓励和帮助残疾高中生及其大学计划。

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.