Transcription factor Mohawk in tendon and ligament degeneration and regeneration

描述（由申请人提供）：肌腱和韧带是源自中胚层的致密结缔组织，连接肌肉与骨骼或骨与骨，传递机械力。细胞外基质（ECM）主要由1型胶原组成，以三螺旋多肽链组织，它们结合成原纤维、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能愈合，很少完全恢复。此外，除了损伤外，韧带和肌腱细胞和ECM的衰老相关变化是膝关节骨关节炎或肩袖综合征发生的重要危险因素。肌腱和韧带损伤治疗方法发展的障碍部分是由于对损伤后调节发育、成体组织平衡和再生反应的机制了解有限。我们最近发现Mohawk （Mkx）是肌腱和韧带发育的关键调节因子。Mkx是三氨基酸环延伸超类的非典型同源箱基因的成员。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在成人和小鼠的肌腱细胞和韧带细胞中高度表达，但在衰老或受关节炎影响的关节以及对白细胞介素-1等炎症刺激的反应中，Mkx的表达会降低。这些观察结果支持了我们的假设，即Mkx是成人肌腱和韧带稳态的中枢调节因子，在损伤或衰老和关节炎期间，Mkx的抑制导致修复反应有限，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：确定发育期间和出生后肌腱/韧带细胞中Mkx的靶点和功能。目的2：分析Mkx肌腱/韧带特异性表达的调控机制。目的3：研究Mkx在间充质干细胞的成肌腱分化中的作用及其增强肌腱损伤修复或再生的潜力。该项目的可行性基于几种转基因小鼠系的可用性，包括有条件的Mkx TG和KO小鼠；从成人年龄范围和ACL退变不同阶段的广泛供体获取人类韧带细胞，以及多种全基因组筛选系统。本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，并为开发肌腱和韧带损伤和疾病的新治疗方法奠定基础。

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.