Monitoring cell migration

The migration of cells towards or away from a chemical stimulus, chemotaxis, is extensively studied in cancer research and drug discovery laboratories with several companies producing cell analysis systems. Current systems allow researchers to identify compounds that promote or inhibit chemotaxis but lack the ability to provide mechanistic information about the processes. The new device has overcome these problems by accurately controlling the release of the chemical stimuli allowing cell response to be analysed more accurately than ever before. This control is so specific that the response of a cell to a stimuli coming from a unique direction can be followed. This extra mechanistic information could prove invaluable in studying the mobilisation and deployment of immune cells to sites of inflammation, which is an integral part of the immune response. The new device, described in an early-release Analytical Chemistry​ article, was developed by researchers from the Max Planck Institute in Germany in collaboration with colleagues at Cornell University, US and the University of California. The application of microfluidic techniques to chemotaxis assays has led to high spatial control, however switching between signalling gradients has been at a timescale of minutes - far slower than the majority of intracellular signalling processes. The new device combines microfluidic techniques with the photochemical release of caged signalling molecules to achieve the stimulation of single cells with high resolution in both space and - more importantly - time. Cells are placed in a microfluidic channel under a continuous fluid flow that carries the inert (caged) form of a signalling agent. The agent is then photochemically activated by splitting off the cage by exposure to short wavelength light produced by a laser. This activation is conducted immediately upstream of the cell yielding very short gradient response times of less than 1 second. The cells response can then be recorded using an inverted confocal laser scanning microscope, in this case a Fluoview FV1000 from Olympus. Control over the number of active signalling molecules reaching the cell is achieved by changing: the concentration of the caged compound in the flow, the size and shape of the illuminated region, the intensity of the light source, and the flow speed. The researchers studied the system by initiating membrane translocation of fluorescent proteins in chemotactic Dictoyostelium discoideum​ cells.