Fourier transform infrared imaging and MR microscopy studies detect compositional and structural changes in cartilage in a rabbit model of osteoarthritis

Abstract

Assessment of subtle changes in the primary macromolecular components of cartilage, proteoglycan (PG) and collagen, is critical for the diagnosis of early stages of osteoarthritis (OA), but to date has remained a challenge. In the current study, we induced osteoarthritic cartilage changes in a rabbit model via ligament transection and medial meniscectomy and monitored disease progression with the techniques of infrared fiber optic probe (IFOP) spectroscopy, Fourier transform infrared imaging spectroscopy (FT-IRIS), and magnetic resonance imaging (MRI) microscopy. IFOP studies combined with chemometric partial least squares analysis enabled us to monitor progressive cartilage surface changes from two to twelve weeks post-surgery. FT-IRIS studies of histological sections of femoral condyle cartilage demonstrated that compared to control cartilage, the OA cartilage had significantly reduced PG content 2 and 4 weeks post-surgery, collagen fibril orientation changes 2 and 4 weeks post-surgery, and changes in collagen integrity 2 and 10 weeks post-surgery, but no significant changes in collagen content at any time point. MR microscopy studies found reduced fixed charge density (FCD), reflective of reduced PG content, in the OA cartilage compared to controls 4 weeks post-surgery. In addition, a non-significant trend towards higher apparent MT exchange rate k m was found in the OA cartilage at this time point, suggesting changes in collagen structural features. These two MR findings, for FCD and k m , parallel the FT-IRIS findings of reduced PG content, and altered collagen integrity, respectively. Further, MR microscopy studies at the 12 week time point cartilage found a trend towards longer T 2 values and decreased anisotropy in the deep zone of the OA cartilage, consistent with increased hydration and less ordered collagen. These studies demonstrate that together, FT-IRIS and MR microscopy provide complementary data on compositional changes in articular cartilage at early stages of osteoarthritic degradation.

Vibrational spectroscopy of articular cartilage

“…Decrease in the collagen integrity was detected in arthritic human tibial AC as compared to visually normal ones in the first infrared fiber optic probe study (63). Later, infrared fiber optic probe together with PLS model was used to monitor changes in AC surface after ligament transection and medial menisectomy in rabbit (26). Strong correlations have also been obtained between Infrared fiber optic probe data and histological grading of OA using PLS models (51,64).…”

“…Assignments of NIR (80,84) and FTIR (19,39,50) proteoglycans than the native cartilage (20) and focal degenerative lesions in human osteoarthritic AC contained less proteoglycans than the surrounding healthy tissue (24). The univariate methods are easy to implement, and, therefore, they have been applied in many studies (25)(26)(27)(28)(29)(30)(31)(32). Collagen and proteoglycan concentration and collagen integrity maps produced using the univariate parameters in human tibial AC are shown in Figure 2.…”

Fourier Transform Infrared Imaging Spectroscopy in Biomedicine – Important Things to Consider When Planning a New Experiment

“…However, a multivariate PLS regression model is clearly the most efficient analysis method As a practical example, let us now consider univariate vs multivariate analysis techniques for determination of proteoglycan distribution in articular cartilage tissue. Univariate based solutions for FT-IRIS analyses of spatial proteglycan content in articular cartilage have been used in several studies [30][31][32][33]. We have demonstrated that specificity for cartilage proteoglycans is significantly increased by taking advantage of the increased spectral separation of the second derivative spectroscopy.…”

Comparative study on identification of healthy and osteoarthritic articular cartilages by fourier transform infrared imaging and chemometrics methods

“…The¯ve OA canines underwent an anterior cruciate ligament (ACL) transection surgery in one of the knee joints up to two years ago, which resulted in a classical arthritis. [18][19][20] The protocols and handling of the animals had been approved by the institutional animal care committees. 21 Upon harvesting, the medial tibias in the knee joints were cut by a table saw with a diamond blade.…”