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: 4.66). 08/2007; 15(7):780-8. DOI: 10.1016/j.joca.2007.01.007
Source: PubMed

ABSTRACT 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.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Changes in the composition of the extracellular matrix (ECM) are characteristic of injury or disease in cartilage tissue. Various imaging modalities and biochemical techniques have been used to assess the changes in cartilage tissue but lack adequate sensitivity, or in the case of biochemical techniques, result in destruction of the sample. Fourier transform near infrared (FT-NIR) spectroscopy, has shown promise for the study of cartilage composition. In the current study NIR spectroscopy was used to identify the contributions of individual components of cartilage in the NIR spectra by assessment of the major cartilage components, collagen and chondroitin sulfate, in pure component mixtures. The NIR spectra were obtained using homogenous pellets made by dilution with potassium bromide. A partial least squares (PLS) model was calculated to predict composition in bovine cartilage samples. Characteristic absorbance peaks between 4000 and 5000 cm− 1 could be attributed to components of cartilage, i.e. collagen and chondroitin sulfate. Prediction of the amount of collagen and chondroitin sulfate in tissues was possible within 8% (w/dw) of values obtained by gold standard biochemical assessment. These results support the use of NIR spectroscopy for in vitro and in vivo applications to assess matrix composition of cartilage tissues, especially when tissue destruction should be avoided.
    Matrix Biology 09/2014; 38. DOI:10.1016/j.matbio.2014.07.007 · 3.65 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Among mammalian soft tissues, articular cartilage is particularly interesting because it can endure a lifetime of daily mechanical loading despite having minimal regenerative capacity. This remarkable resilience may be due to the depth-dependent mechanical properties, which have been shown to localize strain and energy dissipation. This paradigm proposes that these properties arise from the depth-dependent collagen fiber orientation. Nevertheless, this structure-function relationship has not yet been quantified. Here, we use confocal elastography, quantitative polarized light microscopy, and Fourier-transform infrared imaging to make same-sample measurements of the depth-dependent shear modulus, collagen fiber organization, and extracellular matrix concentration in neonatal bovine articular cartilage. We find weak correlations between the shear modulus |G(∗)| and both the collagen fiber orientation and polarization. We find a much stronger correlation between |G(∗)| and the concentration of collagen fibers. Interestingly, very small changes in collagen volume fraction vc lead to orders-of-magnitude changes in the modulus with |G(∗)| scaling as (vc - v0)(ξ). Such dependencies are observed in the rheology of other biopolymer networks whose structure exhibits rigidity percolation phase transitions. Along these lines, we propose that the collagen network in articular cartilage is near a percolation threshold that gives rise to these large mechanical variations and localization of strain at the tissue's surface.
    Biophysical Journal 10/2014; 107(7):1721-1730. DOI:10.1016/j.bpj.2014.08.011 · 3.83 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Tendon, ligament, and joint tissues are important in maintaining daily function. They can be affected by disease, age, and injury. Slow tissue turnover, hierarchical structure and function, and nonlinear mechanical properties present challenges to diagnosing and treating soft musculoskeletal tissues. Understanding these tissues in health, disease, and injury is important to improving pharmacologic and surgical repair outcomes. Raman spectroscopy is an important tool in the examination of soft musculoskeletal tissues. This article highlights exciting basic science and clinical/translational Raman studies of cartilage, tendon, and ligament.
    Applied Spectroscopy 11/2014; 68(11). DOI:10.1366/14-07592 · 2.01 Impact Factor

Full-text (2 Sources)

Available from
Jun 3, 2014