Mechanisms of growth plate organization in response to mechanical load

四肢的纵向生长是通过称为生长板的软骨结构进行的 在被称为软骨内骨形成的过程中，每根骨头的末端。它的一个重要特征是 生长板是指组织中的细胞排列成柱状。而骨骼生长的大小 依赖于肥大期间的细胞增殖、基质沉积和细胞增大， 柱子允许骨骼定向生长。据指出，有很大比例的儿童患有 脊髓灰质炎或偏瘫脑瘫所致的一条腿瘫痪 肢体长度差异显著，瘫痪侧短于另一侧。 基于这些观察，我们假设机械负荷调节的功能 生长板。同时还研究了机械载荷对骨改建的影响。 广泛地说，关于负荷对软骨内骨形成和肢体的作用知之甚少。 因此，我们在体内建立了去除后肢机械负荷的模型。 幼鼠因瘫痪而死亡。机械负荷的丧失导致瘫痪肢体的缩短， 生长板中柱状结构的解体和皮质的破坏 细胞内的肌动蛋白结构。关于软骨细胞是如何排列成 这种柱状结构是因为培养中分离的软骨细胞不会排列成柱状和 使用活体模型既耗时又昂贵。此外，还有一些有限的方法 实时查看所涉及的生物过程。在这份R21提案中，我们计划解决 该领域的关键屏障，并开发体外器官培养系统和活细胞成像 测定细胞和基质黏附时蛋白质定位和张力变化的方法 在列形成期间的实时站点。然后我们将说明涉及到的机制是如何 使用这些分析方法可以详细分析加载和空载条件下的柱形成。 了解机械负荷影响生长板的分子机制 功能有望成为未来治疗各种类型肢体长度的策略的依据 精神错乱。

Longitudinal growth of limbs occurs through cartilaginous structures called the growth plate at the ends of each bone in a process called endochondral bone formation. One important feature of the growth plate is that the cells in the tissue align into columns. While the magnitude of bone growth is dependent on cell proliferation, matrix deposition, and cell enlargement during hypertrophy, the columns allow directional growth of the bone. It was noted that a large proportion of children with paralysis in one leg as a result of poliomyelitis or hemiplegic cerebral palsy demonstrated significant limb length discrepancy with the paralyzed limb being shorter than the other limb. Based on these observations we hypothesized that mechanical load regulates the function of the growth plate. While the effects of mechanical load on bone remodeling have been studied extensively, little was known about the role of loading on endochondral bone formation and limb length determination so we developed in vivo models for removing mechanical load on hind limb in young mice via paralysis. Loss of mechanical load resulted in shortening of the paralyzed limb, disorganization of the columnar architecture in the growth plate, and disruption to the cortical actin structure within the cells. Very little is known about how chondrocytes align themselves into this columnar structure because isolated chondrocytes in culture do not align into columns and in vivo models are time consuming and expensive to work with. In addition, there are limited methods to view the biological processes involved in real time. In this R21proposal we plan to address a critical barrier in the field and develop an ex vivo organ culture system and live cell imaging assays to measure changes in protein localization and tension at cellCcell and cellCmatrix adhesion sites during column formation in real time. We will then illustrate how the mechanisms involved in column formation in loaded and unloaded conditions can be analyzed in detail using these assays. Understanding the molecular mechanisms that govern how mechanical load affects growth plate function would be expected to inform future strategies for treating various types of limb length disorders.