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Cortical cell stiffness is independent of substrate mechanics.

ABSTRACT: Cortical stiffness is an important cellular property that changes during migration, adhesion and growth. Previous atomic force microscopy (AFM) indentation measurements of cells cultured on deformable substrates have suggested that cells adapt their stiffness to that of their surroundings. Here we show that the force applied by AFM to a cell results in a significant deformation of the underlying substrate if this substrate is softer than the cell. This 'soft substrate effect' leads to an underestimation of a cell's elastic modulus when analysing data using a standard Hertz model, as confirmed by finite element modelling and AFM measurements of calibrated polyacrylamide beads, microglial cells and fibroblasts. To account for this substrate deformation, we developed a 'composite cell-substrate model'. Correcting for the substrate indentation revealed that cortical cell stiffness is largely independent of substrate mechanics, which has major implications for our interpretation of many physiological and pathological processes.

SUBMITTER: Rheinlaender J

PROVIDER: S-EPMC7610513 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Cortical cell stiffness is independent of substrate mechanics.

Rheinlaender Johannes J Dimitracopoulos Andrea A Wallmeyer Bernhard B Kronenberg Nils M NM Chalut Kevin J KJ Gather Malte C MC Betz Timo T Charras Guillaume G Franze Kristian K

Nature materials 20200525 9

Cortical stiffness is an important cellular property that changes during migration, adhesion and growth. Previous atomic force microscopy (AFM) indentation measurements of cells cultured on deformable substrates have suggested that cells adapt their stiffness to that of their surroundings. Here we show that the force applied by AFM to a cell results in a significant deformation of the underlying substrate if this substrate is softer than the cell. This 'soft substrate effect' leads to an underes ...[more]

PMID: 32451510

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Project description:Treating recurrent GBM is a clinical challenge due to its highly resistant and aggressive nature. In order to develop new therapeutic targets for recurrent GBM a better understanding of its molecular landscape is necessary. Here we used a cellular model, developed in our lab which generates paired primary and recurrent samples from GBM cell lines and primary patient samples hence allowing us to compare the molecular differences between the two populations. Total RNA seq analysis of parent and recurrent population of two cell lines and one patient sample revealed a significant upregulation of Extracellular matrix interaction in recurrent population. Since matrix stiffness plays a pivotal role in cell-ECM interaction and downstream signaling, we developed a system that mimicked the brain like substrate stiffness by using collagen coated polyacrylamide-based substrate whose stiffness can be modified from normal brain (0.5kPa) to tumorigenic (10kPa). Using these substrates, we were able to capture the morphological and physiological differences between parent and recurrent GBM which were not evident on plastic surfaces (~1 GPa). On 0.5kPa, unlike circular parent cells, recurrent GBM cells showed two morphologies (circular and elongated). The recurrent cells growing on 0.5kPa also showed higher proliferation, invasion, migration and in-vivo tumorigenicity in orthotropic GBM mouse model, compared to parent cells. Furthermore, recurrent cells exhibited elevated velocity irrespective of substrate stiffness, which indicated that recurrent cells may possess inherent differential mechanosignalling ability which was reflected by higher expression of ECM proteins like Collagen IVA, MMP2 and MMP9. Moreover, mice brain injected with recurrent cells grown on 0.5kPa substrate showed higher Young’s modulus values suggesting that recurrent cells conditioned on 0.5kPa make the surrounding ECM stiffer. Importantly, inhibition of EGFR signaling, that is amplified with tissue stiffening in GBM resulted in decreased invasion, migration and proliferation in 0.5kPa recurrent cells, but interestingly survival remained unaffected, highlighting the importance of mimicking the physiological stiffness of the brain mimicking clinical scenario. Total RNA seq analysis of parent and recurrent cells grown on plastic and 0.5kPa substrate identified PLEKHA7 as significantly upregulated gene specifically in 0.5kPa recurrent sample. Higher protein expression of PLEKHA7 in recurrent GBM as compared to primary GBM was validated in patient biopsies. Accordingly, PLEKHA7 knockdown reduced invasion and survival of recurrent GBM cells. Together, these data provides a model system that captures the differential mechanosensing signals of primary and recurrent GBM cells and identifies a novel potential target specific for recurrent GBM.

Dataset Information

Cortical cell stiffness is independent of substrate mechanics.

Publications

Cortical cell stiffness is independent of substrate mechanics.

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