Analysis of collagen architecture alterations in human ovarian cancer and idiopathic pulmonary fibrosis via SHG pixel based polarization analyses (Conference Presentation)

Abstract

Both ovarian cancer and idiopathic pulmonary fibrosis (IPF) are accompanied by significant collagen remodeling in the respective extracellular matrix (ECM). These diseases have similar attributes and collagen alterations can be probed with the same methods. Remodeling can be reflected in increased collagen concentration, changes in alignment within fibrils and fibers and/or up-regulation of different collagen isoforms. We used pixel-based SHG polarization analyses to discriminate the macro/supramolecular collagen structure in human tissues by: i) determination of the helical pitch angle via the single axis molecular model, ii) dipole alignment within fibrils via anisotropy, and iii) chirality via SHG circular dichroism (SHG-CD). For ovarian cancer, the largest differences were between normal stroma and benign tumors, consistent with gene expression showing Col III is up-regulated in the latter. The tissues also displayed differing SHG anisotropies and SHG-CD responses, consistent with randomization of Col I alignment in fibrils in all tumors. These results collectively indicate the fibril assemblies are distinct in all ovarian tissues and likely result from synthesis of new collagen rather than remodeling of existing collagen. For IPF, the largest change was in the SHG-CD response, indicating the fibrotic collagen has different helical structure than that of normal tissues. Interestingly, for both diseases, no increase in Col IIII was found, in contrast to previous reports by immunostaining. We suggest these polarization-based metrics could form the basis of a new classification scheme and complement conventional classification based on genetic profiles and conventional histology for these diseases as well as other cancers and fibroses.