Mechanobiology of Joint Morphogenesis: Manipulating Salamander Limbs

机械力在骨骼关节发育中起作用。关节运动或机械力的改变可导致关节畸形或发育不良。在这个项目中，我们将研究机械力在蝾螈关节发育中的作用，蝾螈是一种能够再生四肢的蝾螈。肢体再生使用与生长相同的发育过程，但在（再）生长过程中提供了一个可以操纵机械和生化环境的环境。我们将确定：1)缺乏运动；2)运动改变，3)在肢体生长过程中缺乏对运动的细胞反应。计算模型将用于确定肢体发育的机械和生化环境，预测关节形状的变化，并与实验关节形状进行比较。这项研究将有助于阐明机械力在关节发育中的作用，参与响应关节机械环境的细胞信号机制，以及如何操纵机械环境来改变关节形状。我们的外联部分的目标是激发人们对机械生物学在肢体再生的背景下。我们将利用东北大学丰富的STEM外展中心，该中心有助于招聘、后勤和外展活动的规划。例如，在这个项目的过程中，我们将通过东北大学的青年学者计划培训高中生，该计划将高中生（通常是代表性不足的少数民族）安排到实验室进行暑期研究。新的动物模型，蝾螈（墨西哥蝾螈），将用于探索机械信号和这些信号的细胞转导如何调节肢体形态发生。从理论上讲，循环静水应力影响生物分子运输，渗透应力影响软骨中的离子通道信号。这些机械因素在机械环境转化为生物反应中起着至关重要的作用。我们将研究肢体去神经支配的影响，组织移植导致肢体反向弯曲，以及再生过程中在水中使用钆抑制离子信号。将生成实验的计算模型，以确定机械应力和生化扩散梯度，并模拟软骨形态发生。这项工作将结合组织水平的有限元模型和生物分子反应的反应/扩散方程，特别是对软骨生长至关重要的Ihh-PTHrP途径。通过将动物实验与计算模型相结合，可以探索关节形态发生过程中关键的机械和生化信号（及其相互作用）。

Mechanical forces play a role in skeletal joint development. Alterations in motion or mechanical forces at the joint can result in joint deformity or dysplasia. In this project we will examine the role of mechanical forces in joint development in the axolotl, a salamander capable of regenerating its limbs. Limb regeneration uses the same developmental processes as growth, but facilitates an environment in which the mechanical and biochemical environment can be manipulated during (re)growth. We will determine the role of 1) lack of motion; 2) altered motion, and 3) lack of cellular response to motion during limb growth. Computational models will be used to determine the mechanical and biochemical environment of the developing limb, to predict changes in shape of the joint, and to compare with experimental joint shapes. This research will help to elucidate the role of mechanical forces in joint development, the cellular signaling mechanisms that are involved in responding to the joint's mechanical environment, and how the mechanical environment can be manipulated to alter joint shape. The objective of our outreach component is to excite people about mechanobiology in the context of limb regeneration. We will tap into the rich Center for STEM Outreach at Northeastern, which aids in recruitment, logistics, and planning of outreach activities. For example, during the course of this project, we will train high school students through Northeastern's Young Scholar Program, which places high school students (often underrepresented minorities) into labs for summer research.The novel animal model, the axolotl (Mexican salamander), will be used to explore how mechanical signals and cellular transduction of those signals regulate limb morphogenesis. It is theorized that cyclic hydrostatic stress influences biomolecular transport and osmotic stress influences ion channel signaling in cartilage. These mechanical factors play a critical role in transduction of the mechanical environment into a biological response. We will examine the effect of: limb denervation, tissue grafting resulting in a reverse flexing limb, and inhibition of ion signaling using gadolinium in the water during regeneration. Computational models of the experiments will be generated to determine mechanical stresses and biochemical diffusion gradients and simulate cartilage morphogenesis. This work will combine a tissue level finite element model with reaction/diffusion equations for biomolecular reactions, particularly the Ihh-PTHrP pathway that is critical to cartilage growth. By combining animal experiments with computational modeling the critical mechanical and biochemical signals (and their interaction) can be explored during joint morphogenesis.