Vidal Benedicto de Campos, Mello Maria Luiza S
Department of Structural and Functional Biology, Institute of Biology, University of Campinas (Unicamp), 13083-862, Campinas, SP, Brazil.
PLoS One. 2016 Mar 25;11(3):e0151989. doi: 10.1371/journal.pone.0151989. eCollection 2016.
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.
使用傅里叶变换红外（FT-IR）显微光谱技术对大鼠耳软骨进行了研究，以拓展目前已针对相对更为复杂的软骨类型所确立的知识。将耳软骨细胞外基质（ECM）的FT-IR光谱与已发表的关于关节软骨、胶原蛋白II和4-硫酸软骨素标准品的数据进行了比较，同时还将含I型胶原蛋白的真皮胶原束（CBs）与II型胶原蛋白进行了比较。通过组织化学方法揭示了耳软骨ECM中的糖胺聚糖（GAGs），并且在睾丸透明质酸酶消化后，ECM的FT-IR光谱带高度（1140 - 820 cm-1）降低。尽管耳软骨比关节软骨的结构更简单，但使用偏光显微镜显示，它含有具有大分子取向的ECM成分。在耳软骨的立体排列中起结构作用的II型胶原蛋白和GAGs，对其FT-IR光谱有贡献。与关节软骨类似，耳软骨显示蛋白聚糖对胶原蛋白酰胺I光谱区域有贡献，这一发现表明该区域不适合用于II型胶原蛋白的定量分析。与关节软骨不同，在耳软骨的FT-IR光谱图中，1064 cm-1处的-SO3-基团对称伸缩振动似乎表现不足。由于对应于-SO3-基团不对称伸缩振动的谱带（1236 - 1225 cm-1）与酰胺III谱带重叠，因此不建议用于评估-SO3-对耳软骨ECM的FT-IR光谱的贡献。相反，对于此目的，1027 - 1016 cm-1处的峰（或肩峰）可能更适合考虑。此处计算的酰胺I/酰胺II比率以及文献数据表明，与纯II型胶原蛋白相比，耳软骨ECM的蛋白质复合物以较低的螺旋构象排列。目前的结果可能会促使人们在涉及耳软骨的病理或实验状态下对该组织进行进一步研究。
