Investigating modes of cartilage cell size regulation and fate during endochondral ossification

项目摘要/摘要 骨骼是脊椎动物解剖学的重要组成部分，用来保护重要的软组织和器官，如 以及允许稳定和移动的功能系统。骨骼的发育与维护 元素需要不同来源和功能的组织类型之间的协调相互作用。理解 这些生物过程背后的机制对于我们理解身体如何 开发并用于临床干预，以应对畸形或伤害。软骨对眼球的发育至关重要 开发骨骼特征，奠定模型作为未来骨骼的基础。分化软骨 细胞，或软骨细胞，经历细胞肥大，迅速增加细胞大小，作为一种促进 四肢的伸长。肥大的软骨细胞在发育过程中也发挥着独特而重要的作用。 血管生成和招募造血干细胞来产生血细胞。尽管它们在许多方面都很重要 发育过程中，软骨细胞肥大的细胞机制还不是很清楚 明白了。这项建议的目的是了解肥大的软骨细胞如何经历细胞 骨骼发育过程中的变化。为了回答这个基本的生物学问题， 提出了以下目标：1)使用实时成像来表征肥大的软骨细胞的命运 方法：2)研究不同细胞命运的软骨细胞肥大模式。这 研究将使用一种新的成像系统(受激拉曼散射显微镜)来量化干质量 完整生长板中肥大的软骨细胞内的密度，从而表征细胞大小的模式 在软骨内骨化过程中增加。此外，我将使用活体外植体成像来进行 肥大软骨细胞向成骨细胞转分化的纵向研究。差异化的能力 细胞向其他谱系的过渡在很大程度上是一种未被探索的生物学现象，将会引起人们的兴趣 更广泛的学科。综上所述，从这项工作中获得的洞察力将导致对 肥大软骨细胞的大小调节及其对骨发育的影响。重要的是 这项工作将通过阐明肥大的作用来揭示与人类健康相关的细胞机制。 软骨细胞在骨骼系统的构图、生长和维持中的作用，这将适用于 发育异常以及损伤修复。

PROJECT SUMMARY / ABSTRACT The skeleton is an essential part of vertebrate anatomy, serving to protect vital soft tissues and organs, as well as a functional system allowing for stability and movement. The development and maintenance of skeletal elements requires coordinated interactions between tissue types of diverse origin and function. Understanding the mechanisms underlying these biological processes is essential to both our understanding of how the body develops and for clinical interventions in response to malformations or injuries. Cartilage is crucial to the development of skeletal features, laying down models as the foundation of future bone. Differentiated cartilage cells, or chondrocytes, undergo cellular hypertrophy to rapidly increase cellular size as a means to facilitate elongation of the limbs. Hypertrophic chondrocytes also serve in unique and important capacities in developing vasculature and recruiting hematopoietic stem cells to produce blood cells. Despite their importance in multiple developmental processes, the cellular mechanisms underlying chondrocyte hypertrophy are not well understood. The objective of this proposal is to understand how hypertrophic chondrocytes undergo cellular changes over the course of skeletal development. In order to answer this fundamental biological question, the following aims are proposed: 1) Characterize the fate of hypertrophic chondrocytes using a live-imaging approach; 2) Investigate modes of hypertrophy in chondrocytes exhibiting different cellular fates. This study will employ a novel imaging system (Stimulated Raman Scattering microscopy) to quantify dry-mass density within hypertrophic chondrocytes in the intact growth plate, thereby characterizing modes of cell size increase during endochondral ossification. Further, I will use ex vivo imaging of live explants to perform a longitudinal study of hypertrophic chondrocyte-to-osteoblast transdifferentiation. The ability of differentiated cells to transition to other lineages is a largely unexplored biological phenomenon and will be of interest across broader disciplines. Taken together, the insight gained from this work will lead to a clearer understanding of cell size regulation in hypertrophic chondrocytes and their influence on the development of bone. Importantly, this work will inform on cellular mechanisms relevant to human health by clarifying the role of hypertrophic chondrocytes in patterning, growth and maintenance of the skeletal system, which will be applicable both for developmental abnormalities as well as injury repair.