Collagen III differential roles in temporal regulation of tendon healing across ages

由于高度排列、致密的胶原蛋白基质，肌腱可以承受很大的力。然而，他们的低点 损伤后细胞密度和相对无法招募修复细胞，以及对过量的敏感性 瘢痕形成会导致肌腱结构和机械功能的丧失。I型胶原(COL1)是主要的 健康肌腱的胶原和III型胶原(Col3)是一种次要成分，随着 受伤。在其他富含Col1的组织中，如皮肤和骨骼，Col3通过调节 早期的细胞渗透促进愈合，以及胶原沉积、结构和交联物 形成，支持COL3在伤口愈合中的早期关键作用，这在肌腱中尚未被研究。 除了了解Col3在肌腱中的作用外，老化组织中的Col3水平也降低了 在老化的肌腱中，我们已经显示出愈合不良，这增加了年龄导致Col3丢失的可能性 增加了老年人群肌腱愈合不良的易感性。而Col3可以协调细胞 肌腱损伤后早期对最佳修复反应至关重要的活动和命运，其 在重塑阶段的持续表达可能会损害预期的愈合反应。因此，我们的 总体目标是描述COL3的时间表达调节损伤的机制 在肌腱愈合过程中的反应，以及它在老化过程中的不同效果。具体地说，我们将测试 Col3对肌腱早期愈合至关重要的假说，但其在重建过程中的持续表达 是有害的。为了测试这一点，我们产生了一种新的可诱导的Col3缺陷(即Col3a1F/，Col3a1F/F)小鼠 通过时间靶向确定COL3的剂量依赖效应的模型。使用这种方法，我们 将确定Col3在肌腱愈合过程中的调节作用，在损伤的早期 增殖期和重塑期间。此外，通过敲除年轻人、中年人和老年人中的Col3 我们将用改变的Col3评估衰老对肌腱愈合的影响。了解企业的角色 在整个愈合过程中，Col3将导致临床相关的见解，以改善肌腱损伤后的预后 不同年龄的患者。本研究的目的是：目标1：确定COL3的年龄敏感机制作用(S 在整个肌腱愈合过程中，在肌腱受伤时击倒Col3。目标2：阐明年龄- COL3在指导修复细胞活动中的敏感机制作用(S)和敲门的延长效应 在肌腱愈合的增殖期下降Col3。目标3：定义年龄敏感机制 在肌腱愈合的重塑阶段，Col3在肌腱修复中的作用(S)。这 这项研究将确定Col3在整个衰老过程中对肌腱损伤做出反应的关键时间角色。我们将利用 一种新的小鼠模型结合严格的层次结构/功能分析来确定Col3在 指导肌腱愈合过程中细胞活动和基质组装/组织之间的相互作用。

Tendons can withstand large forces due to a highly aligned, dense collagen matrix. However, their low cellularity and relative inability to recruit reparative cells post-injury, as well as susceptibility to excessive scarring results in loss of tendon structure and mechanical function. Type I collagen (Col1) is the primary collagen of healthy tendon and type III collagen (Col3) is a minor constituent that increases in response to injury. In other Col1-rich tissues such as skin and bone, Col3 directs reparative cell activities by regulating early cellular infiltration to promote healing, as well as collagen deposition, architecture and crosslink formation, supporting an early critical role of Col3 in wound healing, which has not been studied in tendon. Adding to the importance of understanding a role for Col3 in tendon, Col3 levels in aging tissues are reduced and in aged tendon, we have shown inferior healing which raises the possibility that age-induced Col3 loss increases susceptibility to poor tendon healing in aging populations. While Col3 may orchestrate cellular activities and fate that are critical for an optimal reparative response post-injury at early stages in tendon, its persistent expression in the remodeling phase may compromise the desired healing response. Therefore, our overall objective is to delineate mechanisms by which the temporal expression of Col3 modulates the injury response throughout tendon healing, as well as its differential effect throughout aging. Specifically, we will test the hypothesis that Col3 is crucial for early tendon healing, but that its continued expression during remodeling is detrimental. To test this, we generated a novel inducible Col3 deficient (i.e., Col3a1F/+, Col3a1F/F) mouse model to determine the dose-dependent effects of Col3 by temporal targeting of Col3. Using this approach, we will define the regulatory roles of Col3 throughout tendon healing at the time of injury, during the early proliferative phase, and during remodeling. In addition, by knockdown of Col3 in young, middle-aged, and old animals, we will evaluate the effects of aging on tendon healing with altered Col3. Understanding the role of Col3 throughout healing will lead to clinically relevant insights to improve outcomes following tendon injury in patients of varying ages. The study aims are: Aim 1: To define the age-sensitive mechanistic role(s) of Col3 throughout tendon healing by knocking down Col3 at the time of tendon injury. Aim 2: To elucidate the age- sensitive mechanistic role(s) of Col3 in directing reparative cell activities and prolonged effects of knocking down Col3 during the proliferative phase of tendon healing. Aim 3: To define the age-sensitive mechanistic role(s) of Col3 in tendon repair by knocking down Col3 during the remodeling phase of tendon healing. This study will define the critical temporal roles of Col3 in response to tendon injury throughout aging. We will utilize a novel mouse model coupled with rigorous hierarchical structure/function assays to define the role of Col3 in directing interplay between cellular activities and matrix assembly/organization in tendon healing.