Abstract
BackgroundEndoscopy capable of fluorescence observation provides histological information on gastrointestinal lesions. We explored the novel application of low pH-dependent fluorescent dyes for fluorescence observation of crypt structure and inflammatory cell infiltration in the colon.MethodsLow pH-dependent fluorescent dyes were applied to the colonic mucosa of normal mice for observation under fluorescence stereomicroscopy system. We also examined mouse models of colitis, which were induced by trinitrobenzenesulfonic acid, dextran sulfate sodium or interleukin-10 deficiency.ResultsTopical application of low pH-dependent fluorescent dyes revealed crypts as ring-shaped fluorescent stains by visualizing the mucin granules of goblet cells. Because of the minimal fluorescence intensity of the low pH-dependent fluorescent dyes in phosphate-buffered saline, it was not necessary to wash the mucosa before the fluorescence observation. 4-Nitro-7-piperazino-2,1,3-benzoxadiazole (NBD-PZ) was quicker to achieve complete staining (three minutes) than LysoSensor Green DND-153 and DND-189 (20 minutes). In each type of colitis, NBD-PZ revealed the destruction of the crypts as the disappearance of the ring-shaped fluorescent stains and the infiltration of inflammatory cells as the aggregation of punctate fluorescent stains through visualization of lysosomes.ConclusionsLow pH-dependent fluorescent dyes, especially NBD-PZ, are suitable for topical application to the colonic mucosa and have characteristics that allow for the histological examination of colitis.
Highlights
Endoscopy capable of fluorescence observation provides histological information on gastrointestinal lesions
The mucin granules in goblet cells in the colon contain acid mucopolysaccharides [9], which are stained with Alcian blue (Fig. 1A, right panel), indicating that the intraluminal pH of the mucin granules is relatively low
The mucosa was soaked in phosphate-buffered saline (PBS) alone or containing 1 μg/ml NBD-PZ, incubated at 37°C for three minutes, and observed under fluorescence stereomicroscopy system (Olympus, Tokyo, Japan)
Summary
Endoscopy capable of fluorescence observation provides histological information on gastrointestinal lesions. Novel technologies for endoscopy provide diagnostic information that cannot be obtained with conventional endoscopy to accurately assess gastrointestinal lesions so that the appropriate medical treatment can be applied. Recent advances in endoscopy technologies have taken advantage of fluorescence, including confocal laser endoscopy [2,3,4] and autofluorescence-based endoscopy [5,6]. The responsible fluorophores are not well defined apart from a few molecules such as collagen and reduced nicotinamide [5].
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