Imaging and analysis of perivascular nerves in human mesenteric and coronary arteries: a comparison between epi-fluorescence and confocal microscopy

Perivascular nerves supplying human arteries can be visualised after immunohistochemical staining for a variety of markers. The pattern and density of perivascular nerves vary with region, age and disease. Quantification of the nerve plexus, which may be performed by image analysis, is a prerequisite to assess differences in nerve density. The use of epi-fluorescence microscopy (EFM) presents difficulties in visualising the nerve plexus in certain tissues, which can affect the reliability with which specific staining can be localised and distinguished from non-specific staining. In this study, confocal scanning laser microscopy (CSLM) was used in parallel with EFM, in order to compare images from both techniques. In a comparison of identical areas of nerve plexuses of human mesenteric and coronary arteries stained for protein gene product (PGP) 9.5 and imaged using CSLM and EFM, higher values for area percent (area occupied by nerves), and intercept density (ID/mm, which reflects the number of nerve bundles detected) were found in CSLM images. Similar comparisons of unmatched epi-fluorescence and confocal images from a group of 45 mesenteric arteries revealed no significant difference for area percent, but significantly higher values for ID/mm in CSLM images. These findings illustrate that the better image quality in CSLM influences image analysis and can be very useful in studies of dynamic changes in nerve plexuses. We recommend CSLM for tissues that suffer from high background staining, such as human mesenteric and coronary arteries.