Tendon-dependent Control of Longitudinal Bone Growth

 描述（由申请方提供）：纵向骨生长不成比例增加导致四肢、前胸和脊柱严重畸形，是马凡氏综合征（MFS）患者的临床特征，MFS是一种由细胞外基质（ECM）蛋白和TGFβ调节因子β 1突变引起的结缔组织疾病。我们对具有组织特异性消融Fbn 1基因活性的小鼠的初步研究揭示了肌腱/韧带（T/L）功能障碍和纵向骨过度生长（LBO）之间的意外因果关系。具体来说，我们发现：（1）Fbn 1在T/L细胞中的失活对于促进与生长板（GP）基因表达失调相关的线性骨过度生长是必要的，并且是充分的;（2）Rehapin-1缺陷的肌腱显示出异常的组织结构和受损的机械性能，特别是在骨插入部位;（3）Rehapin-1的相对量与肌腱力学的离散变化相关;（4）肌腱来源的干/祖细胞（TSPC）培养物缺乏Rheumin-1， TGFβ潜在激活增加的结果;（5）通常观察到Rehrin-1缺陷肌腱的异位肌腱钙化。因此，我们假设，通过ECM组织和TGF β 1调节的TSPC分化的控制，通过指定肌腱的机械特性，Replanin-1组件通常限制GP驱动的邻近骨骼的线性生长。因此，我们的建议的范围是双重的;首先，表征TGF-I缺陷如何转化为肌腱功能障碍和肌腱相关的LBO，其次，确定肌腱中的局部TGF β过度活跃如何促进组织变性，从而导致相邻的结构正常的骨的过度线性生长。为此，我们将表征T/L基质中的Rheumin-1缺陷小鼠中肌腱发育和成熟的分子和细胞决定因素的表达，此外还采用计算方法来鉴定这些肌腱缺陷动物GP中可能的致病分子异常（目的1）;应用数据驱动的统计模型，以确定分级的Rehrin-1缺陷如何与肌腱力学和相关的LBO相关（目标2）;并评估全身性TGFβ中和是否改变了Rg-1缺陷小鼠的肌腱病理学和LBO严重程度（目的3）。这些调查的结果，预计将大大推进我们有限的了解肌腱功能的健康和疾病，并隐含的细胞，分子和组织因素，协调出生后的肌肉骨骼组织的生长。

 DESCRIPTION (provided by applicant): A disproportionate increase of longitudinal bone growth that causes serious malformations of the limbs, anterior chest and spine is the clinical hallmark of patients afflicted with Marfan syndrome (MFS), a connective tissue disease caused by mutations in the extracellular matrix (ECM) protein and TGFβ regulator fibrillin-1. Our preliminary studies of mice with tissue-specific ablated Fbn1 gene activity have revealed an unsuspected causal relationship between tendon/ligament (T/L) dysfunction and longitudinal bone overgrowth (LBO). Specifically, we found that (1) Fbn1 inactivation in T/L cells was necessary and sufficient to promote linear bone overgrowth associated with dysregulated growth plate (GP) gene expression; (2) fibrillin-1-deficient tendons displayed abnormal tissue architecture and impaired mechanical properties, particularly at bone- insertion sites; (3) the relative amount of fibrillin-1 correlated with discrete changes in tendon mechanics; (4) tendon-derived stem/progenitor cell (TSPC) cultures deficient for fibrillin-1 differentiated improperly as result of increased latent TGFβ activation; and (5) ectopic tendon calcification of fibrillin-1-deficient tendons was commonly observed. We therefore hypothesize that fibrillin-1 assemblies normally restrict GP-driven linear growth of neighboring bones by specifying the mechanical properties of tendons through the control of ECM organization and TGF-regulated TSPC differentiation. Accordingly, the scope of our proposal is two-fold; first, to characterize how fibrillin-1 deficiency translates into tendon dysfunction and tendon-associated LBO, and second, to establish how local TGF hyperactivity in tendons promote tissue degeneration thereby leading to excessive linear growth of the adjacent, structurally normal bones. To this end, we will characterize the expression of molecular and cellular determinants of tendon development and maturation in mice deficient for fibrillin-1 in T/L matrices, in addition to employing computational approaches to identify probable disease-causing molecular abnormalities in the GP of these tendon-defective animals (Aim 1); apply data-driven statistical models to determine how graded fibrillin-1 deficiencies correlate with tendon mechanics and associated LBO (Aim 2); and assess whether systemic TGFβ neutralization modifies tendon pathology and LBO severity in fibrillin-1-deficient mice (Aim 3). The results of these investigations are expected to substantially advance our limited understanding of tendon function in health and disease and implicitly, of the cellular, molecular and tissue factors that coordinate the postnatal growth of musculoskeletal tissues.