Assaying How Phagocytic Success Depends on the Elasticity of a Large Target Structure
Assaying How Phagocytic Success Depends on the Elasticity of a Large Target Structure
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DOI：
10.1016/j.bpj.2019.08.043
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发表时间：
2019-10-15
影响因子：
3.4
通讯作者：
Gordon, Vernita D.
中科院分区：
文献类型：
--
作者：
Davis-Fields, Megan;Bakhtiari, Layla A.;Gordon, Vernita D.
生物膜感染可以由比中性粒细胞大一个数量级的细菌聚集体组成，中性粒细胞是密集包围聚集体但不进入的吞噬性免疫细胞。由于中性粒细胞太小，无法吞噬整个聚集体，因此如果要利用吞噬作用清除感染，它必须能够分离并一次吞噬几个细菌。目前的研究技术并没有提供一种方法来确定吞噬的成功，这里定义为完全吞噬一块外来物质，取决于一个更大的物体的机械特性，在被吞噬之前，这块物体必须被移除。本文介绍了实现这种方法的一个步骤。通过改变聚合物浓度或交联密度，厘米大小凝胶的弹性模量在以前从临床细菌分离物中生长的铜绿假单胞菌生物膜的测量范围内变化。从健康成年志愿者新鲜抽取的血液中分离出人类中性粒细胞，将其暴露于含有嵌入珠粒的凝胶中1小时，然后从凝胶中取出。收集的中性粒细胞中含有先前在凝胶内的珠粒的百分比用于测量成功的吞噬吞噬。琼脂糖凝胶中聚合物浓度的增加和海藻酸盐凝胶中交联密度的增加都与吞噬吞噬成功率的降低有关。在绘制显示成功吞噬的中性粒细胞百分比作为它们所应用的凝胶弹性模量的函数时，发现海藻酸盐和琼脂糖凝胶的数据都崩溃在同一曲线上。这表明凝胶力学可能会影响吞噬的成功，并表明该实验是朝着实现测量大靶点或嵌入小靶点的大结构的力学如何影响吞噬吞噬成功的方法迈出的一步。
Biofilm infections can consist of bacterial aggregates that are an order of magnitude larger than neutrophils, phagocytic immune cells that densely surround aggregates but do not enter them. Because a neutrophil is too small to engulf the entire aggregate, it must be able to detach and engulf a few bacteria at a time if it is to use phagocytosis to clear the infection. Current research techniques do not provide a method for determining how the success of phagocytosis, here defined as the complete engulfment of a piece of foreign material, depends on the mechanical properties of a larger object from which the piece must be removed before being engulfed. This article presents a step toward such a method. By varying polymer concentration or cross-linking density, the elastic moduli of centimeter-sized gels are varied over the range that was previously measured for Pseudomonas aeruginosa biofilms grown from clinical bacterial isolates. Human neutrophils are isolated from blood freshly drawn from healthy adult volunteers, exposed to gel containing embedded beads for 1 h, and removed from the gel. The percentage of collected neutrophils that contain beads that had previously been within the gels is used to measure successful phagocytic engulfment. Both increased polymer concentration in agarose gels and increased cross-linking density in alginate gels are associated with a decreased success of phagocytic engulfment. Upon plotting the percentage of neutrophils showing successful engulfment as a function of the elastic modulus of the gel to which they were applied, it is found that data from both alginate and agarose gels collapse onto the same curve. This suggests that gel mechanics may be impacting the success of phagocytosis and demonstrates that this experiment is a step toward realizing methods for measuring how the mechanics of a large target, or a large structure in which smaller targets are embedded, impact the success of phagocytic engulfment.