Abstract 18128: Prediction of Elastin Degradation in Aorta Using a Novel Infrared Spectroscopic Methodology

Introduction: In vivo quantification of elastin degradation has significant implication in advancing diagnosis of abdominal aortic aneurysm (AAA) expansion. We hypothesize that Fourier transform infrared spectroscopy (FTIR) can be used to predict elastin content using a methodology that has the potential for assessing elastin degradation in a clinical setting. Here, a model of AAA was created by varying levels of enzymatic degradation in pig aorta and a multivariate model was developed based on acquired FTIR spectra of the specimens. This model was further validated in human AAA sections. Methods: Porcine aorta specimens (n=54) were cut into strips of 100 mg and divided into groups of elastase treated, collagenase treated or untreated by submerging them in enzyme or buffer solutions for different durations. After treatment, samples were cut into half for biochemical assay (Fastin elastin assay) and FTIR. For latter, 9 μm cross sections of frozen tissue were mounted on low-e slides and were scanned with an FTIR spectrometer. Average spectra of specimens were combined with values of elastin content from assay, to develop a partial least squares (PLS) regression model. To further validate, factor-1 matrix of model, was used as reference spectrum in a correlation map to visualize elastin in a section of human AAA wall. This specimen was excised from an aneurysm patient during their elective surgical repair, paraffin embedded, and sectioned on low-e and glass slides, for FTIR analysis and histology. Results and Conclusion: The multivariate model predicted elastin content of the specimens (varying between 0% and 80% d/w) with a strong correlation (R 2 =0.81) and could be used to map elastin in human AAA wall sections (Figure). In conclusion, our developed methodology predicts elastin degradation in the imaging modality of FTIR. Expanding this method to fiber optic modality has a potential for clinical assessment of elastin degradation in a minimally invasive fashion.