The vascular endothelium is a complex single layered network of cells which signal via the release of Ca2+ ions; the study of endothelial cell function and interactions in response to stimuli provides useful information for medical research into, for example, hypertension, diabetes and heart failure. A side viewing GRIN imaging system has previously been used to view calcium signalling in the endothelium  utilising a low numerical aperture GRIN rod and microscope objective to increase the imaging depth and image a large number of cells over the curved inner artery surface. This allows cells to be imaged in near-physiological conditions, as opposed to imaging of flattened arteries; however, the use of GRIN lenses introduces optical aberrations. Resolution is also limited from using a low numerical aperture system.
In this work we investigate this important imaging challenge further with a view to compensating for both the cylindrically-curved geometry of the arteries and field-aberrations present in the optical system. The field aberrations in the imaging optics and resulting from the curved surface/planar sensor mismatch are quantified to allow for corrections to be made through introducing field curvature and aberration correction into the imaging path. This new instrumentation opens up the potential to image calcium signalling within large numbers of cells to try and understand the complex patterns which are produced in response to a range of stimuli.
All blood vessels are lined with a single layer of endothelia cells which play a vital role in controlling the vessels in terms of blood flow, angiogenesis, vascular remodelling, response to pressure changes and blood borne chemical markers. Traditionally such responses to stimuli are examined in isolated cells, in a vascular preparation in which the vessels are opened up to lie flat or using relatively slow confocal or non-linear microscopy from the outside. We have developed a miniature probe that enables high speed, widefield imaging from within an intact pressurised vessel.
This presentation will discuss the development of a 750 micron diameter probe which views orthogonally to the main optical axis to provide sub-cellular resolution images of around 300 cells in an intact, curved artery with the ability to rapidly change focus. Results of the imaging performance will be presented along with the biological context illustrating how this novel imaging modality when coupled with computational modelling enabled a new insight into the biological signalling processes within an intact vessel. By combining this new imaging system with a novel image processing pipeline results will be presented illustrating that the response to certain agonists is affected by pressure and the changing shape of the cells controls this response during a pressure rise. The work illustrates the way that an interdisciplinary approach bringing together novel optics, image processing, computational simulation and biology can lead to insights in the life sciences.