In vivo single-fiber reflectance spectroscopy (SfRS) was performed on an orthotopic AY-27 rat bladder
urothelial cell carcinoma model to explore potential spectroscopic features revealing neoplastic changes. AY-27
bladder tumor cells were intravesically instilled in four rats and allowed to implant and grow for one week, with
two additional rats as the control. A total of 107 SfRS measurements were taken from 27 sites on two control
bladders and 80 from four AY-27 treated bladders. The spectral profiles obtained from AY-27 treated bladders
revealed various levels of a methemoglobin (MetHb) characteristic spectral feature around 635nm. A multisegment
spectral analysis method estimated concentrations of five chromophore compositions including
oxyhemoglobin, deoxyhemoglobin, MetHb, lipid and water. The total hemoglobin concentration ([HbT]), the
MetHb proportion in the total hemoglobin and the lipid volume content showed possible correlations. The 80
measurements from the AY-27 treated bladders could separate to three sub-sets according to the MetHb
proportion. Specifically, 72 were in subset 1 with low proportion (5.3%<[MetHb]<7%), 6 in subset 2 with
moderate proportion (7%<[MetHb]<30%), and 2 in subset 3 with significant proportion (>30%). When grouped
according to [MetHB], the [HbT] increased from 368 μM of subset 1 to 488 μM of subset 2 to 541 μM of subset
3, in comparison to the 285 μM of the control. The increased total hemoglobin and the elevation of MetHb
proportion may signify angiogenesis and degradation in hemoglobin oxygen-transport. Additionally, the lipid
volume content decreased from 2.58% in the control to <0.2% in the tumor groups, indicating disruption of subepithelium
tissue architecture.
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