How do Cavity Macrophages Migrate?

非常原始的生物体有一个充满液体的腔或袋。动物也有重要器官所在的腔体。它们之间的共同联系是，在所有这些空腔中都生活着一种特殊的细胞，即海胆等简单生物体内的体腔细胞，以及老鼠等更发达动物体内的巨噬细胞。具有讽刺意味的是，我们对腔体细胞迁移到腔体中的扰动并修复组织或吞噬入侵细菌的了解很多，而在哺乳动物中，我们对腔体中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腔（其中包含肝脏，脾脏，肠道等）中分离出来，因此已经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，我们发表了第一批关于这些细胞在体内的功能研究之一，并表明当一个关键器官受到干扰时，这些细胞会迁移到该部位并帮助愈合。然而，对于这些细胞在正常条件下的行为以及它们如何检测到扰动的发生，几乎一无所知。最后，在腹腔感染期间，这些巨噬细胞消失，新的小巨噬细胞从骨髓中进入，帮助根除感染。到目前为止，在不打开腔体的情况下是不可能看到这些细胞的，那时一切都被打乱了。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，而不必做任何手术。我们假设，在正常情况下，巨噬细胞像警察一样在腹腔巡逻，不断检查所有器官是否有扰动。我们将使用新的双光子显微镜来评估它们是游泳、爬行还是自由漂浮在器官之间。如果它们在组织上爬行，它们需要“手”（粘附蛋白）。我们会弄清楚这些粘附蛋白是什么。如果器官受到干扰，巨噬细胞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；同样的原理可能不适用于腔液。使用我们强大的显微镜，我们将探索信号分子和粘附分子，使它们能够移动到扰动的位置。最后，我们还将探讨在细菌入侵期间这些腹膜巨噬细胞发生了什么，即巨噬细胞消失反应。我们将使用成像来确定它们是否真的离开腔体并消失，或者只是瞬间牢固地粘在腔体表面，因此不再在液体中发现。这些研究将促进我们对这些在所有无脊椎动物和脊椎动物物种中发现的神秘细胞的生物学理解。我们将提供这些腔巨噬细胞在正常情况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.