title: Infrared microspectroscopic determination of collagen cross-links in articular cartilage.
abstract: Collagen forms an organized network in articular cartilage to give tensile stiffness to the tissue. Due to its long half-life, collagen is susceptible to cross-links caused by advanced glycation end-products. The current standard method for determination of cross-link concentrations in tissues is the destructive high-performance liquid chromatography (HPLC). The aim of this study was to analyze the cross-link concentrations nondestructively from standard unstained histological articular cartilage sections by using Fourier transform infrared (FTIR) microspectroscopy. Half of the bovine articular cartilage samples ( n = 27 ) were treated with threose to increase the collagen cross-linking while the other half ( n = 27 ) served as a control group. Partial least squares (PLS) regression with variable selection algorithms was used to predict the cross-link concentrations from the measured average FTIR spectra of the samples, and HPLC was used as the reference method for cross-link concentrations. The correlation coefficients between the PLS regression models and the biochemical reference values were r = 0.84 ( p < 0.001 ), r = 0.87 ( p < 0.001 ) and r = 0.92 ( p < 0.001 ) for hydroxylysyl pyridinoline (HP), lysyl pyridinoline (LP), and pentosidine (Pent) cross-links, respectively. The study demonstrated that FTIR microspectroscopy is a feasible method for investigating cross-link concentrations in articular cartilage.
authors.affiliation: University of Oulu, Research Unit of Medical Imaging, Physics and Technology, Faculty of Medicine, Oulu, FinlandbUniversity of Eastern Finland, Department of Applied Physics, Kuopio, Finland.
authors.forename: Lassi
authors.initials: L
authors.lastname: Rieppo
authors.affiliation: South Karelia Central Hospital, Department of Radiology, Lappeenranta, Finland.
authors.forename: Harri T
authors.initials: HT
authors.lastname: Kokkonen
authors.affiliation: University of Eastern Finland, Department of Applied Physics, Kuopio, Finland.
authors.forename: Katariina A M
authors.initials: KA
authors.lastname: Kulmala
authors.affiliation: University of Jyväskylä, Department of Health Sciences, Jyväskylä, Finland.
authors.forename: Vuokko
authors.initials: V
authors.lastname: Kovanen
authors.affiliation: Umeå University, Department of Integrative Medical Biology, Umeå, SwedenfHealth Science Center of Xi'an Jiaotong University, School of Public Health, Key Laboratory of Trace Elements and Endemic Diseases, National Health and Family Planning Commission, Xi'an, China.
authors.forename: Mikko J
authors.initials: MJ
authors.lastname: Lammi
authors.affiliation: University of Eastern Finland, Department of Applied Physics, Kuopio, FinlandgKuopio University Hospital, Diagnostic Imaging Center, Kuopio, Finland.
authors.forename: Juha
authors.initials: J
authors.lastname: Töyräs
authors.affiliation: University of Oulu, Research Unit of Medical Imaging, Physics and Technology, Faculty of Medicine, Oulu, FinlandhOulu University Hospital, Department of Diagnostic Radiology, Oulu, FinlandiUniversity of Oulu and Oulu University Hospital, Medical Research Center Oulu, Oulu, Finland.
authors.forename: Simo
authors.initials: S
authors.lastname: Saarakkala
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000737:chemistry* / Q000473:pathology*; D002417:Cattle; D003094:Collagen / Q000032:analysis*; D017127:Glycation End Products, Advanced / Q000378:metabolism; D016018:Least-Squares Analysis; D013055:Spectrophotometry, Infrared
chemical_list: D017127:Glycation End Products, Advanced; D003094:Collagen