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

项目总结/摘要 骨骼是脊椎动物解剖学的重要组成部分，用于保护重要的软组织和器官， 以及允许稳定性和运动的功能系统。骨骼的发育和维持 元素需要不同起源和功能的组织类型之间的协调相互作用。理解 这些生物学过程背后的机制对于我们理解身体如何 开发和临床干预措施，以应对畸形或损伤。腕关节对于 骨骼特征的发展，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以快速增加细胞大小，作为促进 四肢的伸长。肥大软骨细胞还在发育中发挥独特而重要的作用 血管和招募造血干细胞以产生血细胞。尽管它们在多个领域中的重要性 在发育过程中，软骨细胞肥大的细胞机制并不清楚 明白本提案的目的是了解肥大软骨细胞如何进行细胞分化， 骨骼发育过程中的变化。为了回答这个基本的生物学问题， 提出了以下目的：1）使用实时成像来表征肥大软骨细胞的命运 方法; 2）研究表现出不同细胞命运的软骨细胞的肥大模式。这 研究将采用一种新的成像系统（受激拉曼散射显微镜）来定量干物质 完整生长板中肥大软骨细胞内的密度，从而表征细胞大小的模式 在软骨内骨化过程中增加。此外，我将使用活外植体的离体成像来执行 肥大软骨细胞向成骨细胞转分化的纵向研究。分化能力 细胞过渡到其他谱系是一个很大程度上未探索的生物学现象， 更广泛的纪律。总而言之，从这项工作中获得的洞察力将使我们对 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细胞的作用， 软骨细胞在骨骼系统的形成、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.