In vivo analysis of mucosal lipids reveals histological disease activity in ulcerative colitis using endoscope-coupled Raman spectroscopy
The goal of this study is to evaluate endoscopic Raman spectroscopy as a noninvasive technique to determine histological inflammatory status of colitis. Colon mucosal composition was investigated in vivo from patients with ulcerative colitis (UC) and from age- and body mass index (BMI) matched controls using endoscope-coupled Raman spectroscopy. The results were co-registered with histological assessment of inflammatory status at the same locations. Substantial decreases (50-60%) in the content of phosphotidylcholines (PCs) and total lipids were observed in inflamed colon tissue (histology grade 1, 2 and 3) compared to those from the quiescent (histology grade 0) and from the controls. No significant difference was observed in lipids or PC contents between control and grade 0, or among grades 1 – 3. The degree of lipid unsaturation increased in the inflamed tissue regardless of disease severity. The inflammation-associated alterations in lipids and PC are observed independent of BMI or the anatomical locations for data collection. Multivariate analysis using support vector machine (SVM) algorithm classified the spectra of the controls or the inactive colitis from those of inflamed tissue with a sensitivity of 83.5% and 97.1% respectively. Our results showed that mucosal lipid content is related to the microscopic disease activity, and thus could serve as a valuable spectral marker to differentiate active colitis from the quiescent.