Investigating the role of the primary cilium in muscle regeneration

骨骼肌是一种重要的组织，不仅对运动员或年轻人，而且对每个人的日常生活都是如此。随着年龄的增长，我们的肌肉质量和力量会逐渐减少，为了保持身体健康和良好的生活质量，保持肌肉健康是很重要的。这种组织在受伤后具有惊人的自我修复能力，肌肉可以自我重建，例如，在通过锻炼长期固定之后。这种再生能力取决于肌肉中存在的干细胞数量。这些干细胞被称为卫星细胞(SC)，它们驻留在肌肉中一个特殊的位置，称为‘小窝’。SC通常处于静止(不活跃)状态，但它们会对身体发出的信号做出反应，激活并开始繁殖。干细胞的后代将分化成更多的肌肉，但也会重新进入利基，以便在一生中维持干细胞池。干细胞被激活后，它们沿着肌肉纤维向损伤部位迁移，然后修复损伤部位。随着年龄的增长，我们失去了一些干细胞，剩下的干细胞在产生更多肌肉方面变得不那么有效。因此，了解如何保持这些细胞的健康是很重要的。我们发现，干细胞有一个叫做初级纤毛的细胞突起，它充当重要信号的“天线”。其中一个信号是Sonic hedgehog蛋白(Shh)，我们知道它需要一个初级纤毛才能被细胞感知。我们创造了一种独特的小鼠品系，设计成携带突变的干细胞，这种突变的干细胞缺乏初级纤毛。我们发现，这会导致受伤后肌肉再生效率大大降低，肌肉纤维变薄。我们的发现表明，激活Shh通路可能对肌肉疾病有潜在的治疗效果，或者有助于维持老年人的肌肉功能。首先，我们需要更详细地研究初级纤毛和Shh如何影响SC功能-这就是这个项目的目的。我们将检查突变的干细胞激活、分裂、迁移、分化和重新进入其利基的能力。如果干细胞没有纤毛，也可能会死亡，我们将测试是否可以通过注射一种激活Sonic Hedgehog信号通路的药物来改善肌肉修复。我们做这些实验所需要的所有方法都在我们的实验室里建立起来了。除了修复机制的详细描述外，我们还将检查在没有初级纤毛的干细胞中发生的分子变化，特别是我们将询问哪些基因因此而表达不同。这将提供更多的重要见解，并可能揭示肌肉疾病的潜在新治疗靶点，或有助于维持老年人和体弱者的健康组织。

Skeletal muscle is an important tissue, not only for athletes or young people, but for everyone during their everyday life. As we get older our muscle mass and strength tends to diminish and to support continued physical health and a good quality of life it is important to keep muscle healthy. This tissue has an amazing ability to repair itself after injury and muscle can rebuild itself, for example after long-term immobilization by doing exercise. This regenerative capacity depends on a population of stem cells that is present in muscle. These stem cells are called satellite cells (SC) and they reside in a specialised location, called a 'niche', within the muscle.The SC are normally quiescent (inactive), but in response to signals from the body they become activated and begin to multiply. The descendents of SCs will differentiate into more muscle, but also re-enter the niche in order to maintain the pool of stem cells throughout life. After SCs are activated they migrate along muscle fibres towards sites of injury, which they then repair. As we get older we lose some of our SCs and the remaining ones become less efficient at generating more muscle. So it is important to understand how to keep these cells healthy. We have found that SCs have a cellular protrusion called a primary cilium, which acts as an 'antenna' for important signals. One such signal is the Sonic hedgehog protein (Shh), which we know needs a primary cilium to be sensed by the cells. We have created a unique line of mice, engineered to carry mutant SCs, which lack a primary cilium. We showed that this leads to much less efficient muscle regeneration, with thinner muscle fibres, after injury. Our finding suggests that activating the Shh pathway may have potential therapeutic benefits for muscle diseases, or help sustain muscle function in the elderly.First we need to investigate in more detail how the primary cilium and Shh affect SC function - and this is what this project is about. We will examine the ability of the mutant SCs to become activated, to divide, to migrate, to differentiate, to re-enter their niche. It is also possible that SCs die if they don't have a cilium and we will test if muscle repair can be improved by injecting a drug that activates the Sonic hedgehog signalling pathway. All the methods we need to do these experiments are established in our laboratories. In addition to the detailed characterization of the repair mechanism we will examine the molecular changes that happen in SCs that do not have a primary cilium, specifically we will ask which genes are expressed differently as a result. This will give additional important insights and may reveal potential novel therapeutic targets in muscle disease, or help to maintain a healthy tissue in elderly and frail people.