A Novel Technology for Simultaneous Tensile Loading and High-Resolution Imaging of Cells

Engineering a uniaxial substrate-stretching device for simultaneous electrophysiological measurements and imaging of strained peripheral neurons

Peripheral nerves are continuously subjected to mechanical strain during everyday movements, but excessive stretch can lead to damage and neuronal cell functionality can also be impaired. To better understand cellular processes triggered by stretch, it is necessary to develop in vitro experimental methods that allow multiple concurrent measurements and replicate in vivo mechanical conditions. Current commercially available cell stretching devices do not allow flexible experimental design, restricting the range of possible multi-physics measurements. Here, we describe and characterise a custom-built uniaxial substrate-straining device, with which neurons cultured on aligned patterned surfaces (50 µm wide grooves) can be strained up to 70% and simultaneously imaged with widefield and confocal imaging (up to 100x magnification). Furthermore, direct and indirect electrophysiological measurements by patch clamping and calcium imaging can be made during strain application. We characterise the strain applied to cells cultured in deformable wells by using finite element method simulations and experimental data, showing local surface strains of up to 60% with applied strains of up to 25%. We also show how patterned substrates do not alter the mechanical properties of the system compared to unpatterned surfaces whilst still inducing a homogeneous cell response to strain. The characterisation of this device will be useful for research into investigating the effect of whole-cell mechanical stretch on neurons at both single cell and network scales, with applications found in peripheral neuropathy modelling and in platforms for preventive and regenerative studies.

Deformable 96-well cell culture plate compatible with high-throughput screening platforms

Adherent cells such as endothelial cells sense applied mechanical stretch to adapt to changes in their surrounding mechanical environment. Despite numerous studies, signaling pathways underlying the cellular mechanosensing and adaptation remain to be fully elucidated partly because of the lack of tools that allow for a comprehensive screening approach. Conventionally, multi-well cell culture plates of standard configurations are used for comprehensive analyses in cell biology study to identify key molecules in a high-throughput manner. Given that situation, here we design a 96-well cell culture plate made of elastic silicone and mechanically stretchable using a motorized device. Computational analysis suggested that highly uniform stretch can be applied to each of the wells other than the peripheral wells. Elastic image registration-based experimental evaluation on stretch distributions within individual wells revealed the presence of larger variations among wells compared to those in the computational analysis, but a stretch level of 10%–that has been employed in conventional studies on cellular response to stretch—was almost achieved with our setup. We exposed vascular smooth muscle cells to cyclic stretch using the device to demonstrate morphological repolarization of the cells, i.e. typical cellular response to cyclic stretch. Because the deformable multi-well plate validated here is compatible with other high-throughput screening-oriented technologies, we expect this novel system to be utilized for future comprehensive analyses of stretch-related signaling pathways.

A polymeric cell stretching device for real-time imaging with optical microscopy

This paper reports the design, fabrication and characterization of a cell stretching device based on the side stretching approach. Numerical simulation using finite element method provides a guideline for optimizing the geometry and maximizing the output strain of the stretched membrane. An unique PDMS-based micro fabrication process was developed for obtaining high parallelization, well controlled membrane thickness and an ultra-thin bottom layer that is crucial for the use with confocal microscopes. The stretching experiments are fully automated with both device actuation and image acquisition. A programmable pneumatic control system was built for simultaneous driving of 24 stretching arrays. The actuation signals are synchronized with the image acquisition system to obtain time-lapse recording of cells grown on the stretched membrane. Experimental results verified the characteristics predicted by the simulation. A platform with 15 stretching units was integrated on a standard 24 mm × 50 mm glass slide. Each unit can achieve a maximum strain of more than 60 %. The platform was tested for cell growth under cyclic stretching. The preliminary results show that the device is compatible with all standard microscopes.