Ex Vivo Fluorescence Imaging of Normal and Malignant Urothelial Cells to Enhance Early Diagnosis

Urinary cytology is a noninvasive and unconstraining technique for urothelial cancer diagnosis but lacks sensitivity for detecting low-grade lesions. In this study, the fluorescence properties of classical Papanicolaou-stained urothelial cytological slides from patients or from cell lines were monitored to investigate metabolic changes in normal and tumoral cells. Time- and spectrally-resolved fluorescence imaging was performed at the single cell level to assess the spectral and temporal properties as well as the spatial distribution of the fluorescence emitted by urothelial cells. The results reveal quite different fluorescence distributions between tumoral urothelial cells, characterized by a perimembrane fluorescence localization, and the normal cells which exhibit an intracellular fluorescence. This is not caused by differences in the fluorescence emission of the endogenous fluorophores NAD(P)H, flavoproteins or porphyrins but by various localization of the EA 50 Papanicolaou stain as revealed by both the spectral and time-resolved parameters. The present results demonstrate that the use of single-cell endofluorescence emission of Papanicolaou-stained urothelial cytological slides can allow an early ex vivo diagnosis of low-grade bladder cancers.