Atomic Force Microscopy Is a Potent Technique to Study Eosinophil Activation

Abstract

Eosinophils are multifunctional cells with several functions both in healthy individuals, and those with several diseases. Increased number and morphological changes in eosinophils have been correlated with the severity of an acute asthma exacerbation. We measured eosinophils obtained from healthy controls and individuals with acute asthma using atomic force microscopy (AFM). In the control samples, cells showed more rounded morphologies with some spreading, while activated cells from symptomatic individuals were spreading, and presenting emission of multiple pseudopods. Eosinophils presenting separate granules close to the cells suggesting some degranulation was also increased in asthma samples. In comparison to histopathological techniques based on brightfield microscopy, AFM showed considerably more details of these morphological changes, making the technique much more sensitive to detect eosinophil morphological changes that indicate functional alteration of this cell. AFM could be an important tool to evaluate diseases with alterations in eosinophil functions.

Functional blood cell analysis by label-free biosensors and single-cell technologies

“…Importantly, these eosinophils were fixed directly after venous blood sampling. In a similar study in which healthy and acute asthma donors' eosinophils were allowed to spread on glass at 37 • C (where eosinophils likely activate by adhesion) a marked difference was observed in their spreading and morphology when measured by AFM [209]. Although this conclusion was based on very few samples, this approach highlights the need to study cells in a functional setting.…”

Uncovering the cytotoxic effects of air pollution with multi-modal imaging of in vitro respiratory models

“…Scale bars are 5 µm. Adapted from Eaton et al ([ 156 ], fig. 1 d,e , g,h ); copyright 2019, Frontiers in Physiology; .…”

“…In situ functional assessment of a variety of human muscle fibres [ 169 ] found that AFM measurements could reliably distinguish biopsies from both Duchene muscular dystrophy and Becker muscular dystrophy patients when compared with matched healthy individuals [ 169 ]. AFM has been employed to investigate morphological features of cells [ 170 ], where it can be used to evaluate morphological differences between asthmatic and healthy individuals [ 156 ]. In symptomatic asthmatic whole blood samples, it was shown that many highly activated eosinophils were present, with AFM identifying irregular spreading with multiple pseudopods when compared with the healthy samples, which appeared more round with less spreading [ 156 ] ( figure 4 c ).…”

“…AFM has been employed to investigate morphological features of cells [ 170 ], where it can be used to evaluate morphological differences between asthmatic and healthy individuals [ 156 ]. In symptomatic asthmatic whole blood samples, it was shown that many highly activated eosinophils were present, with AFM identifying irregular spreading with multiple pseudopods when compared with the healthy samples, which appeared more round with less spreading [ 156 ] ( figure 4 c ). Eosinophil recruitment and the presence of granular proteins are considered biomarkers for monitoring allergic inflammatory disorders, such as asthma [ 171 ].…”