Flow Shear Induced Changes in Membrane Fluidity: Dependence on Cell- Substrate Adhesion Strength

Tamal Das, Tapas K. Maiti, Suman Chakraborty

Abstract

Besides the internal genetic content and the chemical exchanges with external tissue environment, the physical interactions of cancer cells with its microenvironment also provide the guidelines for successful oncogenesis. During its metastatic journey from primary tumor to distant locations of body, a cancer cell is exposed to stresses of diverse origin and kind, of which fluid shear stresses of interstitial and haematogenic nature have been least studied in relation to their impact in cancer progression. Here, we have designed a biomicrofluidic system integrated with microfabrication compatible traction force microscopy facility. It is further compatible with high-resolution visualization by laser scanning confocal microscope. This system enables us to study the flow induced changes in plasma membrane of a representative cancer cell line HeLa as the function of imparted shear stress and importantly, cell-substrate adhesion strength. Using the device, we are able to reveal novel shear induced immediate and late changes in the fluidity of apical plasma membrane. We have shown while transient changes in membrane fluidity depend on the orientation of flow and are largely independent of cellsubstrate adhesion landscape, long term membrane fluidization is controlled by the cell-substrate adhesion strength that is represented by maximum traction stress that cell exerts on the microchannel wall. It is then probed that membrane fluidization probably occurs due to the endocytosis of lipid raft domains. The conclusions drawn from the work, in this respect, are anticipated to provide new directions in cancer research.

Keywords: Cell adhesion, Fluidization, Fluorescence recovery after photobleaching, Lipid raft, Membrane fluidity, Traction force microscopy

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