title: Second harmonic generation microscopy analysis of extracellular matrix changes in human idiopathic pulmonary fibrosis.
abstract: Patients with idiopathic fibrosis (IPF) have poor long-term survival as there are limited diagnostic/prognostic tools or successful therapies. Remodeling of the extracellular matrix (ECM) has been implicated in IPF progression; however, the structural consequences on the collagen architecture have not received considerable attention. Here, we demonstrate that second harmonic generation (SHG) and multiphoton fluorescence microscopy can quantitatively differentiate normal and IPF human tissues. For SHG analysis, we developed a classifier based on wavelet transforms, principle component analysis, and a K-nearest-neighbor algorithm to classify the specific alterations of the collagen structure observed in IPF tissues. The resulting ROC curves obtained by varying the numbers of principal components and nearest neighbors yielded accuracies of >95%. In contrast, simpler metrics based on SHG intensity and collagen coverage in the image provided little or no discrimination. We also characterized the change in the elastin/collagen balance by simultaneously measuring the elastin autofluorescence and SHG intensities and found that the IPF tissues were less elastic relative to collagen. This is consistent with known mechanical consequences of the disease. Understanding ECM remodeling in IPF via nonlinear optical microscopy may enhance our ability to differentiate patients with rapid and slow progression and, thus, provide better prognostic information.
authors.affiliation: University of Wisconsin-Madison, Department of Biomedical Engineering, Madison, Wisconsin 53706, United States.
authors.forename: Karissa
authors.initials: K
authors.lastname: Tilbury
authors.affiliation: University of Wisconsin-Madison, Department of Biomedical Engineering, Madison, Wisconsin 53706, United States.
authors.forename: James
authors.initials: J
authors.lastname: Hocker
authors.affiliation: University of Wisconsin-Madison, Medical Physics Department, Madison, Wisconsin 53706, United StatescMorgridge Institute for Research, Madison, Wisconsin 53715, United States.
authors.forename: Bruce L
authors.initials: BL
authors.lastname: Wen
authors.affiliation: University of Wisconsin, School of Medicine and Public Health Madison, Division of Allergy, Pulmonary, and Critical Care Medicine, Madison, Wisconsin 53706, United States.
authors.forename: Nathan
authors.initials: N
authors.lastname: Sandbo
authors.affiliation: University of Wisconsin-Madison, Department of Biostatistics and Medical Informatics, Madison, Wisconsin 53706, United States.
authors.forename: Vikas
authors.initials: V
authors.lastname: Singh
authors.affiliation: University of Wisconsin-Madison, Department of Biomedical Engineering, Madison, Wisconsin 53706, United StatesbUniversity of Wisconsin-Madison, Medical Physics Department, Madison, Wisconsin 53706, United States.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Campagnola
mesh_terms: D000465:Algorithms; D005109:Extracellular Matrix / Q000473:pathology*; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000473:pathology*; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods*; D008858:Microscopy, Phase-Contrast / Q000379:methods*; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D058067:Wavelet Analysis