Multiphoton imaging 5-ASA metabolism in mouse colon

In collaboration with Marshall H. Montrose and Shaoyo Chu, University of Indiana School of Medicine

The most commonly prescribed drugs for inflammatory bowel diseases are 5-aminosalicylic acid (5-ASA) and its metabolites. The Montrose group has developed ratiometric microscopy methods to image 5-ASA and its major metabolite N-acetyl-5-ASA (As-5-ASA) by single cells in normal and inflamed mouse colon tissues.

Tissue morphology (1) and experimental diagram (2)

The histology of the tissue is well illustrated by the MPM autofluoresence images shown in (1). The lumens of the crypts are contiguous with and yet environmentally distinct from the lumen of the gut (due to diffusional constraints). (2) The perfusion chamber allows oriented introduction of drugs to the lumen or basal lamina sides. The major advantage of MPM in this case arises from the localized nature of the excitation. The therapeutic concentration of 5-ASA is 30mM. Due to absorption events throughout the beam with conventional illumination, confocal microscopy only allows penetration to ~20mm. MPE occurs only in the focal volume and the 5-ASA is transparent to the 700nm excitation. Thus MPM can penetrate ~200 mm.