Transcription factor Mohawk in tendon and ligament degeneration and regeneration

描述（由申请人提供）：肌腱和韧带是中胚层起源的致密结缔组织，连接肌肉与骨骼或骨骼与骨骼，并传递机械力。细胞外基质（ECM）主要由1型胶原组成，其组织为三螺旋多肽链，其结合成原纤维、纤维、束、三级束，形成肌腱和韧带结构。过度使用或受伤造成的肌腱和韧带损伤不会愈合，而且很少完全恢复。此外，对于损伤，韧带和肌腱的细胞和ECM的老化相关变化代表了膝关节骨关节炎或肩袖综合征发展的重要风险因素。解决肌腱和韧带损伤的方法的发展的障碍部分是由于有限的知识机制，调节发展，成人组织体内平衡和损伤后的再生反应。我们最近确定莫霍克（Mkx）作为肌腱和韧带发育的关键调节因子。Mkx是非典型同源异型盒基因的三氨基酸环延伸超类的成员。Mkx-/-小鼠全身肌腱发育不全，清楚地表明Mkx在肌腱发育中的重要功能。重要的是，Mkx在成人和小鼠腱细胞和韧带细胞中高度表达，但其表达在衰老或关节炎影响的关节中以及响应于炎症刺激如白细胞介素-1而降低。这些观察结果支持我们的假设，即Mkx是成人肌腱和韧带稳态的中心调节因子，并且其在损伤后或老化和关节炎期间的抑制导致有限的修复反应并导致退行性变化。为了验证这一假设并揭示Mkx维持和/或再生肌腱/韧带的分子机制，我们将进行以下研究。目的1：在发育期间和出生后确定Mkx靶点和肌腱/韧带细胞中的功能。目的2：分析Mkx在肌腱/韧带特异性表达的调控机制。目标3：检查Mkx在间充质干细胞的肌腱分化中的作用及其增强肌腱损伤修复或再生的潜力。该项目的可行性是基于几种转基因小鼠品系的可用性，包括条件性Mkx TG和KO小鼠;获得来自成人年龄范围内和ACL变性不同阶段的广泛供体的人韧带细胞和多个全基因组筛选系统。这项研究的结果有望促进我们目前对肌腱和韧带生物学的理解，并作为开发肌腱和韧带损伤和疾病新治疗方法的基础。

DESCRIPTION (provided by applicant): Tendons and ligaments are dense connective tissues of mesodermal origin, which connect muscles to bones or bone to bone, and transmit mechanical force. The extracellular matrix (ECM) consists mainly of collagen type 1, organized as triple-helix polypeptide chains, which unite into fibrils, fibers, fascicles, tertiary bundles, forming the tendon and ligament architecture. Damage to tendons and ligaments caused by overuse or injuries is not healed and rarely recovers completely. In addition, to injury, aging-related changes in cells and ECM of ligaments and tendons represent an important risk factor for the development of knee osteoarthritis or rotator cuff syndrome. Obstacles in the development of approaches to address tendon and ligament damage are partly due to the limited knowledge about mechanisms that regulate development, adult tissue homoeostasis and regenerative responses following injury. We recently identified Mohawk (Mkx) as a key regulator of tendon and ligament development. Mkx is a member of the Three Amino acid Loop Extension superclass of atypical homeobox genes. Mkx-/- mice had hypoplastic tendons throughout the body, clearly demonstrating an essential function of Mkx in tendon development. Importantly, Mkx is highly expressed in adult human and mouse tenocytes and ligament cells but its expression is decreased in aging or in arthritis-affected joints and in response to inflammatory stimuli such as interleukin-1. These observations support our hypothesis that Mkx is a central regulator of adult tendon and ligament homeostasis and that its suppression following injury or during aging and arthritis accounts for limited repair responses and leads to degenerative changes. To test this hypothesis and reveal the molecular mechanisms of Mkx to maintain and/or regenerate tendon/ligament, we will perform the following studies. Aim 1: Determine Mkx targets and functions in tendon/ligament cells during development and after birth. Aim 2: Analyze mechanisms controlling tendon/ligament specific expression of Mkx. Aim 3: Examine role of Mkx in tenogenic differentiation of mesenchymal stem cells and its potential to enhance repair or regeneration of tendon injuries. Feasibility of this project is based on availability of several genetically modified mouse lines, including conditional Mkx TG and KO mice; access to human ligament cells from a wide range of donors across the adult age spectrum and at various stages of ACL degeneration and multiple genome-wide screening systems. The findings from this study are expected to advance our current understanding of tendon and ligament biology and serve as a basis for the development of new therapeutic approaches for tendon and ligament injuries and diseases.