Department of Mechanical Engineering, Multiscale in Mechanical and Biological Engineering, University of Zaragoza, 50018, Zaragoza, Spain.
Aragon Institute of Engineering Research, University of Zaragoza, 50018, Zaragoza, Spain.
BMC Microbiol. 2022 Aug 31;22(1):211. doi: 10.1186/s12866-022-02623-w.
Macrophages play an essential role in the process of recognition and containment of microbial infections. These immune cells are recruited to infectious sites to reach and phagocytose pathogens. Specifically, in this article, bacteria from the genus Mycobacterium, Salmonella and Escherichia, were selected to study the directional macrophage movement towards different bacterial fractions. We recreated a three-dimensional environment in a microfluidic device, using a collagen-based hydrogel that simulates the mechanical microarchitecture associated to the Extra Cellular Matrix (ECM). First, we showed that macrophage migration is affected by the collagen concentration of their environment, migrating greater distances at higher velocities with decreasing collagen concentrations. To recreate the infectious microenvironment, macrophages were exposed to lateral gradients of bacterial fractions obtained from the intracellular pathogens M. tuberculosis and S. typhimurium. Our results showed that macrophages migrated directionally, and in a concentration-dependent manner, towards the sites where bacterial fractions are located, suggesting the presence of attractants molecules in all the samples. We confirmed that purified M. tuberculosis antigens, as ESAT-6 and CFP-10, stimulated macrophage recruitment in our device. Finally, we also observed that macrophages migrate towards fractions from non-pathogenic bacteria, such as M. smegmatis and Escherichia coli. In conclusion, our microfluidic device is a useful tool which opens new perspectives to study the recognition of specific antigens by innate immune cells.
巨噬细胞在识别和控制微生物感染的过程中起着至关重要的作用。这些免疫细胞被招募到感染部位，以到达并吞噬病原体。具体来说，在本文中，我们选择了分枝杆菌属、沙门氏菌属和大肠杆菌属的细菌，来研究巨噬细胞对不同细菌成分的定向运动。我们在微流控装置中创建了一个三维环境，使用基于胶原蛋白的水凝胶来模拟与细胞外基质（ECM）相关的机械微结构。首先，我们表明巨噬细胞的迁移受到其环境中胶原蛋白浓度的影响，随着胶原蛋白浓度的降低，迁移速度更快，迁移距离更远。为了重现感染性的微环境，我们使巨噬细胞暴露于从细胞内病原体结核分枝杆菌和伤寒沙门氏菌中获得的细菌成分的侧向浓度梯度中。我们的结果表明，巨噬细胞以浓度依赖的方式，朝着细菌成分所在的部位定向迁移，这表明所有样本中都存在趋化分子。我们证实，纯化的结核分枝杆菌抗原，如 ESAT-6 和 CFP-10，在我们的设备中刺激了巨噬细胞的募集。最后，我们还观察到巨噬细胞向非致病性细菌（如耻垢分枝杆菌和大肠杆菌）的成分迁移。总之，我们的微流控装置是一种有用的工具，为研究先天免疫细胞对特定抗原的识别开辟了新的视角。
