Neutrophil Migration in Three Dimensions

描述（由申请人提供）：中性粒细胞对先天宿主防御至关重要，因此外周血中这些细胞数量的减少会增加对危及生命的感染的易感性。除了产生足够数量的中性粒细胞外，宿主防御还依赖于中性粒细胞有效发挥作用的能力。白细胞粘附缺乏症患者中性粒细胞数量正常，但整合素基因表达不足。慢性肉芽肿病患者的中性粒细胞不能产生足够水平的杀微生物氧化物质。在这两种情况下，这些功能缺陷使患者容易感染机会性病原体，复发性感染发作和伤口愈合受损。另外，过度的中性粒细胞反应可导致以侧支组织损伤为特征的疾病状态，如呼吸窘迫综合征、哮喘、炎症性肠病、缺血/再灌注损伤、血管炎和类风湿性关节炎。因此，中性粒细胞必须对感染或损伤作出充分但精细调节的反应，以促进体内平衡的恢复。中性粒细胞浸润到体内任何受损组织中，以启动炎症反应，而不管不同的身体组织在组成和结构上存在实质性差异。像所有细胞一样，中性粒细胞表达一组特定的细胞表面受体，这些受体在微环境中引发对生物元素的功能性反应。很明显，物理

DESCRIPTION (provided by applicant): Neutrophils are essential to innate host defense such that a decrease in the number of these cells in the peripheral blood presents heightened susceptibility to life threatening infections. In addition to being produced in adequate number, host defense also depends on the ability of neutrophils to function effectively. Patients with Leukocyte Adhesion Deficiency have normal numbers of neutrophils but they are genetically deficient in expression of integrins. Neutrophils in patients with Chronic Granulomatous Disease fail to produce adequate levels of microbiocidal oxidative species. In both cases, these functional deficits predispose patients to infections with opportunistic pathogens, recurrent infectious episodes and impairment of wound healing. Alternatively, an excessive neutrophil response can result in disease states characterized by collateral tissue damage such as respiratory distress syndrome, asthma, inflammatory bowel disease, ischemia/reperfusion injury, vasculitis and rheumatoid arthritis. Therefore, neutrophils must execute a sufficient but finely regulated response to infection or injury to promote a return to homeostasis. Neutrophils infiltrate any compromised tissue in the body in order to initiate an inflammatory response regardless of the fact that different bodily tissues offer substantial variations in composition an structure. Like all cells, neutrophils express a set of specific cell surface receptors that elicita functional response to biological elements within a microenvironment. It is clear that the physical nature of a microenvironment, such as its relative stiffness, is also an important regulator of function. The mechanisms that neutrophils use to respond to physical cues are not as clear as they are for receptor-ligand induced responses. Prior work from our laboratory hypothesized that soft, elastic tissues such as brain, may affect neutrophil function differently than stiffer tissues such as skin or muscle. Indeed, neutrophil adhesion, production of traction forces and migration were significantly different on fibronectin-coated matricies that varied only in stiffnes. The stiffnesses were all within the physiological range of tissue stiffnesses found in the body. Although this model provided a more relevant physiologic substrate than rigid materials such as plastic and glass, it is limited in that inflammatory neutrophils function within a 3-dimensional tissue environment. This is a proposal to engineer a tunable 3D in vitro system that will permit neutrophils to be studied under conditions that more closely model a tissue microenvironment. Moreover, the novelty of our system lies in that a given cell can be tracked in 2-dimensions and then in 3-dimensions thereby isolating dimension as a single experimental variable. Experiments will also determine whether integrins mediate the generation of traction forces and control migration of neutrophils in 3D as compared to 2D systems. A 3D in vitro system that accounts for the salient mechanical features of organs and tissues will provide a better means to predict effectiveness of therapeutics indicated for control of inflammation.