Department of Surgery, Washington University School of Medicine, St. Louis, MO, USA.
J Clin Invest. 2012 Jul;122(7):2499-508. doi: 10.1172/JCI62970. Epub 2012 Jun 18.
Two-photon intravital microscopy has substantially broadened our understanding of tissue- and organ-specific differences in the regulation of inflammatory responses. However, little is known about the dynamic regulation of leukocyte recruitment into inflamed heart tissue, largely due to technical difficulties inherent in imaging moving tissue. Here, we report a method for imaging beating murine hearts using intravital 2-photon microscopy. Using this method, we visualized neutrophil trafficking at baseline and during inflammation. Ischemia reperfusion injury induced by transplantation or transient coronary artery ligation led to recruitment of neutrophils to the heart, their extravasation from coronary veins, and infiltration of the myocardium where they formed large clusters. Grafting hearts containing mutant ICAM-1, a ligand important for neutrophil recruitment, reduced the crawling velocities of neutrophils within vessels, and markedly inhibited their extravasation. Similar impairment was seen with the inhibition of Mac-1, a receptor for ICAM-1. Blockade of LFA-1, another ICAM-1 receptor, prevented neutrophil adherence to endothelium and extravasation in heart grafts. As inflammatory responses in the heart are of great relevance to public health, this imaging approach holds promise for studying cardiac-specific mechanisms of leukocyte recruitment and identifying novel therapeutic targets for treating heart disease.
双光子活体显微镜大大拓宽了我们对组织和器官特异性炎症反应调控的认识。然而，对于白细胞募集到炎症心脏组织的动态调控，我们知之甚少，这主要是由于对移动组织成像的固有技术困难。在这里，我们报告了一种使用活体双光子显微镜对跳动的鼠心进行成像的方法。使用该方法，我们在基线和炎症期间可视化了中性粒细胞的迁移。移植或短暂冠状动脉结扎引起的缺血再灌注损伤导致中性粒细胞募集到心脏，从中冠状动脉渗出，并浸润心肌，在心肌中形成大的簇。含有突变型 ICAM-1（一种对中性粒细胞募集很重要的配体）的移植物心脏降低了血管内中性粒细胞的爬行速度，并显著抑制了其渗出。ICAM-1 受体 Mac-1 的抑制也出现了类似的损伤。另一种 ICAM-1 受体 LFA-1 的阻断可防止中性粒细胞与心脏移植物内皮的黏附和渗出。由于心脏的炎症反应与公共健康密切相关，这种成像方法有望用于研究白细胞募集的心脏特异性机制，并为治疗心脏病确定新的治疗靶点。
