The IsoStretcher – a novel isotropic Strain Device for Mechanobiology
Motivated by the challenge of studying mechanosensitive signaling, e.g. through activation of mechanosensitive ion channels (MsC), in cells of the cardiovascular system, we developed a concept for a strain device that allows to apply cyclic or static isotropic strain to cells adhered to polydimethyl-siloxane (PDMS) elastomer membranes. The requirements for the system were to allow inverted microscopy (whitefield, epi-, confocal fluorescence) simultaneously with stretch and ensure a minimum z-shift of the focal plane to avoid losing cells during stretch. The main objective was also to enable high-content imaging of many cells in a field of view rather than high-resolution analysis of single cells.
The initial IsoStretcher concept involved a circular PDMS membrane connected to six pins that were part of six sliders with two hook pins. The other pin of each slider was inserted into a translation ring containing six oblique groves. Therefore, turning the translation ring by means of an external swivel motor throughh a V-belt mechanism allowed to translate the rotational movement of the translation ring into a radial displacement of the sliders and thus, isotropic stretch of the circular PDMS chamber on top of the stage of a microscope (Schürmann et al. 2016). The IsoStretcher can easily be adapted to different microscope systems through a modular base plate and is well suited for studies of stretch-induced cell reactions, in particular to cells experiencing multi-axial strain in vivo (e.g. lung alveolar cells, gastro-intestinal epithelial cells, urothelium, etc.). In particular, enothelial and epithelial cells adhere well to extracellular matrix-coated and functionalized PDMS membranes (Schürmann et al. 2016). The movie below shows membrane-stained (Evans Blue) live HEK cells during isotropic stretch between 1% and 19% radial displacement without loss of focus (Schürmann et al. 2016).
Labs currently using our IsoStretcher module worldwide include: Victor Chang Cardiac Research Institute, Sydney, Australia (Prof. Martinac); Mayo Clinic, Rochester, US (Prof. Beyder), Biotechnology Institute Thurgau, Switzerland (Dr. Rossy), Virginia Commonwealth University, Richmond, US (Prof. Conway).
Schürmann S, Wagner S, Herlitze S, Fischer C, et al. (2016) The IsoStretcher: An isotropic cell stretch device to study mechanical biosensor pathways in living cells. Biosensors Bioelectron. 81:363-372. doi: 10.1016/j.bios.2016.03.015