How do Cavity Macrophages Migrate?

非常原始的生物体有一个充满液体的腔或袋。动物的重要器官也有洞。共同的联系是，在所有这些空洞中生活着特殊的细胞，在简单的生物中被称为体腔细胞，在海胆等简单生物中，在更发达的动物中，如小鼠，在巨噬细胞中。具有讽刺意味的是，我们对腔体细胞了解很多，这些细胞迁移到腔内的扰动中，修复组织或吃掉入侵的细菌，而在哺乳动物中，对腔内巨噬细胞的生物学知之甚少。相反，由于巨噬细胞相对容易从腹膜腔(包括肝、脾、肠等)分离出来，已发表了数千项关于这些细胞在试管中表达的所有途径和蛋白质的研究。一年半前，我们发表了第一批体内这些细胞的功能研究之一，表明当关键器官受到干扰时，这些细胞会迁移到现场并帮助愈合。然而，对于这些细胞在正常条件下做什么以及它们如何检测到扰动正在发生，几乎一无所知。最后，在腔内的腹膜感染期间，这些巨噬细胞消失，新的小巨噬细胞从骨髓中产生，帮助根除感染。到目前为止，如果不打开腔，就不可能看到这些细胞，在这一点上，一切都被扰乱了。因此，我们购买了一种特殊的显微镜，近红外激光可以深入到腔内，这样我们就可以看到这些细胞，而不需要做任何手术。我们假设，在正常情况下，腹膜巨噬细胞像警察一样在腹膜腔内巡逻，不断检查所有器官的扰动情况。无论它们是游泳、爬行还是自由漂浮在器官之间，将使用我们的新双光子显微镜进行评估。如果它们在组织上爬行，它们需要“手”(黏附蛋白)。我们会弄清楚这些黏附蛋白是什么。如果器官受到干扰，巨噬细胞会迅速检测到干扰，并移动到受影响的部位。我们知道很多关于免疫细胞如何在组织中爬行的知识；同样的原理可能不适用于空洞的液体。使用我们强大的显微镜，我们将探索信号分子和黏附分子，使它们能够移动到扰动位置。最后，我们还将探索这些腹膜巨噬细胞在细菌入侵过程中会发生什么，即巨噬细胞消失反应。我们将使用成像来确定它们是真正离开空洞并消失，还是只是瞬间牢牢地粘在空洞的表面上，因此不再在液体中发现。这些研究将促进我们对在所有无脊椎动物和脊椎动物中发现的这些神秘细胞的生物学的理解。我们将提供有关这些腔巨噬细胞在正常条件下和器官受到干扰时的行为和功能的重要信息。

Very primitive organisms have a cavity or sack filled with fluid. Animals also have cavities where the vital organs reside. The common link is that in all these cavities live specialized cells known as coelomocytes in simple organisms such as sea urchins and macrophages in more developed animals such as mice. Ironically, we know a lot about the coelomocytes that migrate to perturbations in the cavity and repair tissue or eat invading bacteria while in mammals very little is known about the biology of macrophages in the cavities. Instead, because of the relative ease of macrophage isolation from the peritoneal cavity (which harbors the liver, spleen, intestines, etc.), thousands of studies have been published about all the pathways and proteins these cells express in test tubes. A year and a half ago, we published one of the first functional studies on these cells in vivo and showed that when a critical organ is perturbed, these cells migrate to the site and help to heal. However, almost nothing is known about what these cells do under normal conditions and how they detect that a perturbation is occurring. Finally, during a peritoneal infection in the cavity, these macrophages disappear and new small macrophages come in from bone marrow and help to eradicate the infection. To date, it has been impossible to visualize these cells without opening up the cavity and at that point everything is perturbed. As such we have purchased a special microscope where near infrared lasers penetrate deep into the cavity so we can see these cells without having to do any surgery. We hypothesize that peritoneal macrophages patrol the peritoneal cavity like policemen constantly checking all of the organs for perturbations under normal conditions. Whether they swim or crawl or float freely across organs will be assessed using our new two photon microscope. If they are crawling on tissues they need "hands" (adhesive proteins). We will figure out what these adhesive proteins are. If the organ is perturbed the macrophages quickly detect the perturbation and move to the afflicted site. We know lots about how immune cells crawl in tissue; the same principles may not apply in the fluid of cavities. Using our powerful microscope, we will explore the signaling molecules and adhesion molecules that allow them to move to sites of perturbation. Finally, we will also explore what happens to these peritoneal macrophages during bacterial invasion, known as the macrophage disappearance reaction. We will use imaging to determine whether they truly leave the cavity and disappear or just instantaneously stick firmly to the surfaces of the cavity and therefore are no longer found in the fluid. These studies will advance our understanding of the biology of these enigmatic cells found in all species of invertebrates and vertebrates. We will provide important information about how these cavity macrophages behave and function under normal conditions and when organs are perturbed.