Injury Response in Normal and EDS Tendons: Regulatory Roles of Collagen V

描述(由申请人提供)：本提案的总体目标是确定V型胶原在正常和典型Ehler-Danlos综合征(EDS)肌腱损伤反应中的调节作用。从数量上讲，V型胶原是胶原纤维中的一个次要成分，但其表达的调节具有戏剧性的表型效应，表明其具有关键的调节作用。 EDS是一种遗传性结缔组织疾病，具有广泛的结缔组织脆性，典型的表现为皮肤高度伸展，关节松弛不稳定，以及伤口愈合异常。典型的EDS是由V型胶原突变和COL5A1单倍体不足定义的，在~67%的受影响个体中存在。V型胶原还与：跟腱病、前交叉韧带断裂，以及受伤和运动能力不足有关。此外，在肌腱和韧带的损伤反应中观察到V型胶原的上调。我们建立的单倍体不足的V型胶原EDS小鼠模型将用于拟议的研究。然而，由于在整个发育和成熟过程中缺乏V型胶原造成的慢性影响，该模型具有局限性，这些胶原蛋白随后叠加在与损伤反应相关的变化上。因此，这一建议结合了我们的诱导性胶原V缺失和杂合子模型，允许时间靶向的V型胶原表达的调节。第一次，直接研究V型胶原在损伤反应的特定阶段的关键调节作用将是可能的。使用单倍型V型胶原缺乏的EDS模型，我们已经显示出纤维数量减少，纤维结构异常，横截面积减少，指长屈肌腱僵硬程度降低，这与过度活动的EDS表型一致。我们最近使用条件零模型的研究显示，纤维、纤维和肌腱水平的严重结构改变与机械功能严重受损、关节脱位和步态异常相关。在这一建议中检验的一般假设是，肌腱对损伤的反应是由V型胶原介导的机制调节的(S)。目的：(1)明确V型胶原在经典EDS异常肌腱损伤反应中的调节功能改变(S)；(2)阐明V型胶原在正常基质中对肌腱损伤修复反应的机制调节作用(S)；(3)比较V型胶原表达调控对正常和病变/异常肌腱损伤反应的影响。我们的创新方法包括传统的和诱导性的小鼠模型，我们将系统地分析V型胶原在肌腱损伤修复中的调节作用。这一方法将与复杂和创新的机械和组织特性测量相结合，以及成分分布，以得出对损伤反应的机械学理解。这些研究将明确V型胶原在损伤后肌腱结构和功能重建中的特定时间调节作用。此外，这些数据将为开发促进EDS异常伤口愈合的治疗干预措施提供关键基础。

DESCRIPTION (provided by applicant): The overall goal of this proposal is to define the regulatory roles of collagen V in the injury response in normal and classic Ehlers-Danlos syndrome (EDS) tendons. Collagen V is a quantitatively minor component of collagen fibrils, yet modulation of its expression has dramatic phenotypic effects, indicating critical regulatory roles. EDS is a heritable connective tissue disorder with generalized connective tissue fragility and the classic form is characterized by hyperextensible skin, joint laxity and instability, as well as abnormal wound healing. Classic EDS is defined by collagen V mutations with haploinsufficiency for COL5A1 present in ~67% of affected individuals. Collagen V also has been linked to: Achilles tendinopathy, ACL rupture, as well as injury and performance deficiencies. In addition, upregulation of collagen V is observed in the injury response in tendons and ligaments. Our established haploinsufficent collagen V EDS mouse model will be used for the proposed studies. However, this model has limitations due to chronic effects resulting from lack of collagen V throughout development and maturation that are then superimposed on the changes associated with the injury response. Therefore, this proposal incorporates our inducible collagen V-null and heterozygous models that allow for temporal targeting of the modulation of collagen V expression. For the first time, directly studying the critical regulatory roles of collagen V during specific phases of the injury response will be possible. Using the haploinsufficient collagen V EDS model, we have demonstrated reduced fibril number, abnormal fibril structure, decreased cross sectional area, and a reduction in the stiffness of the flexor digitorum longus tendon consistent with the hypermobile EDS phenotype. Our recent work using a conditional null model demonstrated severe structural alterations at the fibril, fiber and tendon level associated with severely compromised mechanical function, joint dislocations and gait abnormalities. The general hypothesis tested in this proposal is that the tendon response to injury is modulated by collagen V mediated mechanism(s). The aims are to: (Aim 1) Define the altered regulatory function(s) of collagen V in the abnormal tendon injury response in classic EDS~ (Aim 2) Elucidate the mechanistic regulatory role(s) of collagen V in the repair response to tendon injury in a normal matrix~ and (Aim 3) Compare the effect of modulation of collagen V expression on the injury response in normal and in diseased/abnormal tendons. Our innovative approach with both conventional and inducible mouse models will systematically analyze the regulatory roles of collagen V on repair of tendon injuries. This approach will be coupled with sophisticated and innovative measures of mechanical and organizational properties, together with compositional profiles, to derive a mechanistic understanding of the injury responses. These studies will define the specific temporal regulatory roles of collagen V in the re- establishment of tendon structure and function in response to injury. In addition, the data will provide a critical foundation for developing therapeutic interventions to enhance the abnormal wound healing in EDS.