title: FT-IR Microspectroscopy of Rat Ear Cartilage.
abstract: Rat ear cartilage was studied using Fourier transform-infrared (FT-IR) microspectroscopy to expand the current knowledge which has been established for relatively more complex cartilage types. Comparison of the FT-IR spectra of the ear cartilage extracellular matrix (ECM) with published data on articular cartilage, collagen II and 4-chondroitin-sulfate standards, as well as of collagen type I-containing dermal collagen bundles (CBs) with collagen type II, was performed. Ear cartilage ECM glycosaminoglycans (GAGs) were revealed histochemically and as a reduction in ECM FT-IR spectral band heights (1140-820 cm-1) after testicular hyaluronidase digestion. Although ear cartilage is less complex than articular cartilage, it contains ECM components with a macromolecular orientation as revealed using polarization microscopy. Collagen type II and GAGs, which play a structural role in the stereo-arrangement of the ear cartilage, contribute to its FT-IR spectrum. Similar to articular cartilage, ear cartilage showed that proteoglycans add a contribution to the collagen amide I spectral region, a finding that does not recommend this region for collagen type II quantification purposes. In contrast to articular cartilage, the symmetric stretching vibration of -SO3- groups at 1064 cm-1 appeared under-represented in the FT-IR spectral profile of ear cartilage. Because the band corresponding to the asymmetric stretching vibration of -SO3- groups (1236-1225 cm-1) overlapped with that of amide III bands, it is not recommended for evaluation of the -SO3- contribution to the FT-IR spectrum of the ear cartilage ECM. Instead, a peak (or shoulder) at 1027-1016 cm-1 could be better considered for this intent. Amide I/amide II ratios as calculated here and data from the literature suggest that protein complexes of the ear cartilage ECM are arranged with a lower helical conformation compared to pure collagen II. The present results could motivate further studies on this tissue under pathological or experimental states involving ear cartilage.
authors.affiliation: Department of Structural and Functional Biology, Institute of Biology, University of Campinas (Unicamp), 13083-862, Campinas, SP, Brazil.
authors.forename: Benedicto de Campos
authors.initials: Bde C
authors.lastname: Vidal
authors.affiliation: Department of Structural and Functional Biology, Institute of Biology, University of Campinas (Unicamp), 13083-862, Campinas, SP, Brazil.
authors.forename: Maria Luiza S
authors.initials: ML
authors.lastname: Mello
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000378:metabolism*; D002809:Chondroitin Sulfates / Q000378:metabolism; D024042:Collagen Type I / Q000378:metabolism; D024043:Collagen Type II / Q000378:metabolism; D004425:Ear Cartilage / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism*; D006025:Glycosaminoglycans / Q000378:metabolism; D051381:Rats; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D024042:Collagen Type I; D024043:Collagen Type II; D006025:Glycosaminoglycans; D002809:Chondroitin Sulfates