title: The ratio 1660/1690 cm(-1) measured by infrared microspectroscopy is not specific of enzymatic collagen cross-links in bone tissue.
abstract: In postmenopausal osteoporosis, an impairment in enzymatic cross-links (ECL) occurs, leading in part to a decline in bone biomechanical properties. Biochemical methods by high performance liquid chromatography (HPLC) are currently used to measure ECL. Another method has been proposed, by Fourier Transform InfraRed Imaging (FTIRI), to measure a mature PYD/immature DHLNL cross-links ratio, using the 1660/1690 cm(-1) area ratio in the amide I band. However, in bone, the amide I band composition is complex (collagens, non-collagenous proteins, water vibrations) and the 1660/1690 cm(-1) by FTIRI has never been directly correlated with the PYD/DHLNL by HPLC. A study design using lathyritic rats, characterized by a decrease in the formation of ECL due to the inhibition of lysyl oxidase, was used in order to determine the evolution of 1660/1690 cm(-1) by FTIR Microspectroscopy in bone tissue and compare to the ECL quantified by HPLC. The actual amount of ECL was quantified by HPLC on cortical bone from control and lathyritic rats. The lathyritic group exhibited a decrease of 78% of pyridinoline content compared to the control group. The 1660/1690 cm(-1) area ratio was increased within center bone compared to inner bone, and this was also correlated with an increase in both mineral maturity and mineralization index. However, no difference in the 1660/1690 cm(-1) ratio was found between control and lathyritic rats. Those results were confirmed by principal component analysis performed on multispectral infrared images. In bovine bone, in which PYD was physically destructed by UV-photolysis, the PYD/DHLNL (measured by HPLC) was strongly decreased, whereas the 1660/1690 cm(-1) was unmodified. In conclusion, the 1660/1690 cm(-1) is not related to the PYD/DHLNL ratio, but increased with age of bone mineral, suggesting that a modification of this ratio could be mainly due to a modification of the collagen secondary structure related to the mineralization process.
authors.affiliation: INSERM, UMR 1033, Lyon, France. delphine.farlay@inserm.fr
authors.forename: Delphine
authors.initials: D
authors.lastname: Farlay
authors.forename: Marie-Eve
authors.initials: ME
authors.lastname: Duclos
authors.forename: Evelyne
authors.initials: E
authors.lastname: Gineyts
authors.forename: Cindy
authors.initials: C
authors.lastname: Bertholon
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Viguet-Carrin
authors.forename: Jayakrupakar
authors.initials: J
authors.lastname: Nallala
authors.forename: Ganesh D
authors.initials: GD
authors.lastname: Sockalingum
authors.forename: Dominique
authors.initials: D
authors.lastname: Bertrand
authors.forename: Thierry
authors.initials: T
authors.lastname: Roger
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Hartmann
authors.forename: Roland
authors.initials: R
authors.lastname: Chapurlat
authors.forename: Georges
authors.initials: G
authors.lastname: Boivin
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001842:Bone and Bones / Q000378:metabolism* / Q000528:radiation effects; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D003094:Collagen / Q000378:metabolism*; D003432:Cross-Linking Reagents / Q000378:metabolism*; D005096:Exostoses / Q000150:complications / Q000378:metabolism / Q000473:pathology; D005260:Female; D007842:Lathyrism / Q000150:complications / Q000378:metabolism / Q000473:pathology; D015591:Microspectrophotometry; D008903:Minerals; D010782:Photolysis / Q000528:radiation effects; D008249:Protein-Lysine 6-Oxidase / Q000378:metabolism*; D011884:Radius / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects; D051381:Rats; D017208:Rats, Wistar; D017550:Spectroscopy, Fourier Transform Infrared; D013977:Tibia / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D000596:Amino Acids; D003432:Cross-Linking Reagents; D008903:Minerals; C015484:pyridinoline; D003094:Collagen; D008249:Protein-Lysine 6-Oxidase