The Depth-dependent Anisotropy of Articular Cartilage by Fourier-Transform Infrared Imaging (FTIRI)

Department of Physics and Center for Biomedical Research, Oakland University, Rochester, MI 48309, USA.
Osteoarthritis and Cartilage (Impact Factor: 4.17). 08/2007; 15(7):780-8. DOI: 10.1016/j.joca.2007.01.007
Source: PubMed


To study the anisotropic characteristics of individual histological zones in articular cartilage using Fourier-transform infrared imaging (FTIRI) at 6.25microm pixel resolution.
A canine humeral cartilage-bone block was paraffin-embedded and microtomed into 6microm sections. Each of the five sections was infrared (IR)-imaged 26 times with identical acquisition parameters, for a 5-10 degrees increment of a wire grid polarizer introduced before the detector in 0-180 degrees angular space. Following the IR imaging experiments, the same tissue sections were also imaged by polarized light microscopy (PLM).
The IR absorption components of cartilage (amide I, amide II, amide III, and sugar) exhibit distinctly different anisotropies, which vary differently as a function of the tissue depth. A new type of image, "the absorbance anisotropy map", was constructed for each major component, which shows that (1) the absorbance of the amide components in most parts of the tissue is anisotropic, (2) the anisotropic behavior in the radial and the superficial zones of the tissue is opposite, (3) the absorption profile of amide I is inverse to those of amide II and amide III, and (4) the IR absorption of the sugar component is almost isotropic. The anisotropic variations of the amide components were fitted to an empirical equation.
The IR anisotropy map is a powerful tool to monitor the individual chemical components in articular cartilage. The ability to examine the same tissue section using both FTIRI and PLM offers the possibility of correlating the tissue's morphology with chemical distribution.

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    • "While FTIRI cannot differentiate types of collagen or recognize advanced glycation end products [11] formed on the collagen, it can distinguish changes in both mineral and matrix maturity. FTIRI has been used to study pharmacologic effects on normal and diseased bone in humans and in various normal and mutant animals [12] [13] [14] [15] [16] [17] [18], cartilage composition and degeneration [19] [20] [21] as well as collagen orientation in cartilage [22]. FTIRI and FTIR microspectroscopy were previously used to provide insights into bone mineralization processes in both fracture healing and in the epiphyseal growth plate [18] [23]. "
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    ABSTRACT: Fourier transform infrared spectroscopic imaging (FTIRI) was used to study bone healing with spatial analysis of various callus tissues in wild type mice. Femoral fractures were produced in 28 male C57BL mice by osteotomy. Animals were sacrificed at 1, 2, 4, and 8 weeks to obtain callus tissue at well-defined healing stages. Following microcomputerized tomography, bone samples were cut in consecutive sections for FTIRI and histology, allowing for spatial correlation of both imaging methods in different callus areas (early calcified cartilage, woven bone, areas of intramembranous and endochondral bone formation). Based on FTIRI, mineral/matrix ratio increased significantly during the first 4 weeks of fracture healing in all callus areas and correlated with bone mineral density measured by micro-CT. Carbonate/phosphate ratio was elevated in newly formed calcified tissue and at week 2 attained values comparable to cortical bone. Collagen maturity and mineral crystallinity increased during weeks 1-8 in most tissues while acid phosphate substitution decreased. Temporal and callus area dependent changes were detected throughout the healing period. These data assert the usefulness of FTIRI for evaluation of fracture healing in the mouse and its potential to evaluate pathologic fracture healing and the effects of therapeutic interventions.
    Journal of Spectroscopy 02/2015; 2015:1-12. DOI:10.1155/2015/659473 · 0.54 Impact Factor
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    • "1-16cm−1) in cartilage [13]. FTIRI can also be very effective in the study of the orientation of the chemical bonds (e.g., amide I bond, which is the C = O in a molecular dipole) in cartilage [14,15], the changes in the collagen orientation due to external loading [16], and the molecular concentrations in cartilage [13,17–19]. The main limitation of FTIRI is its spatial resolution, on the order of 5-10 microns due to its optical properties. "
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    ABSTRACT: Fourier transform infrared imaging (FTIRI) and the attenuated total reflection Fourier transform infrared microimaging (ATR-FTIRM) were used to study the chemical and structural distributions of cellular components surrounding individual chondrocytes in canine humeral cartilage, at 6.25µm pixel resolution in FTIRI and 1.56µm pixel resolution in ATR-FTIRM. The chemical and structural distributions of the cellular components in chondrocytes and tissue can be successfully imaged in high resolution ATR-FTIRM. One can also study the territorial matrix of fine collagen fibrils surrounding the individual chondrocytes by the polarization experiments using the absorption ratio of amide I to amide II bands.
    Biomedical Optics Express 04/2011; 2(4):937-45. DOI:10.1364/BOE.2.000937 · 3.65 Impact Factor
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    • "The articular layer exhibits compositional heterogeneity from the surface to the subchondral bone; it is typically divided into three regions commonly called the superficial, middle and deep zones (SZ, MZ and DZ, respectively) (Maroudas, 1979; Mow and Ratcliffe, 1997). The delineation between these zones is often determined on the basis of the orientation of the collagen fibrils, which may be determined via polarized light microscopy (PLM), magnetic resonance imaging (MRI), or Fourier Transform infra-red imaging (FTIRI) (Bi et al., 2005; Nieminen et al., 2001; Nissi et al., 2006; Xia et al., 2007; Xie et al., 2008). "
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    ABSTRACT: Over the last two decades, considerable progress has been reported in the field of cartilage mechanics that impacts our understanding of the role of interstitial fluid pressurization on cartilage lubrication. Theoretical and experimental studies have demonstrated that the interstitial fluid of cartilage pressurizes considerably under loading, potentially supporting most of the applied load under various transient or steady-state conditions. The fraction of the total load supported by fluid pressurization has been called the fluid load support. Experimental studies have demonstrated that the friction coefficient of cartilage correlates negatively with this variable, achieving remarkably low values when the fluid load support is greatest. A theoretical framework that embodies this relationship has been validated against experiments, predicting and explaining various outcomes, and demonstrating that a low friction coefficient can be maintained for prolonged loading durations under normal physiological function. This paper reviews salient aspects of this topic, as well as its implications for improving our understanding of boundary lubrication by molecular species in synovial fluid and the cartilage superficial zone. Effects of cartilage degeneration on its frictional response are also reviewed.
    Journal of Biomechanics 07/2009; 42(9):1163-76. DOI:10.1016/j.jbiomech.2009.04.040 · 2.75 Impact Factor
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