Imaging the vascular wall using confocal microscopy.

Blood vessels are capable of structural changes in a dynamic process called 'vascular remodelling', which involves cell growth, death, phenotypic change and migration, as well as extracellular matrix synthesis and degradation. An integrated view of the interrelationships of the different elements of the arterial wall is made possible by fluorescence confocal microscopy which enables collection of serial optical sections of relatively thick specimens without the need to cut them as with conventional histology. With the aid of image analysis software, these serial sections can be further reconstructed to obtain 3-D images, where the structures of interest are localized and quantified. Confocal microscopy can be combined with pressure myography to obtain, simultaneously, information on vascular function and 3-D structure at near-to-physiological conditions. There are a vast number of fluorescent compounds useful for imaging vessel structure and function. Nuclear dyes allow the identification of the different types of vascular cells and the quantification of their number, shape and orientation. The speed of confocal image acquisition and processing makes it possible to scan entire intact arteries stained with fluorescent kits or antibodies to locate infrequent events such as cell apoptosis, proliferation or migration. Confocal microscopy is not only useful for imaging vascular wall structure, but also to visualize and quantify, by the intensity of fluorescence, the generation of vascular cell factors such as nitric oxide or superoxide anion. In conclusion, confocal microscopy and image analysis software provide insight into vascular wall structure and function and the active process of vascular remodelling in physiological and pathological situations.