Specificity of Fourier Transform Infrared (FTIR) Microspectroscopy to Estimate Depth-Wise Proteoglycan Content in Normal and Osteoarthritic Human Articular Cartilage

Saarakkala, Simo; Julkunen, Petro

doi:10.1177/1947603510368689

Cited by 25 publications

(27 citation statements)

References 20 publications

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“…The findings of the present study indicate that the largest absolute prediction errors occur in the deep tissue, where the PG and collagen contents are high. In contrast, it was earlier found that the specificity of univariate-based PG parameters is limited in the superficial tissue of normal and especially of osteoarthritic human AC, while they work reasonably well in the middle and deep layers [13]. The most probable explanation for this discrepancy is that different species were used in the studies.…”

Section: Discussionmentioning

confidence: 86%

Fourier Transform Infrared Spectroscopic Imaging and Multivariate Regression for Prediction of Proteoglycan Content of Articular Cartilage

Rieppo

Jurvelin

et al. 2012

PLoS ONE

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Fourier Transform Infrared (FT-IR) spectroscopic imaging has been earlier applied for the spatial estimation of the collagen and the proteoglycan (PG) contents of articular cartilage (AC). However, earlier studies have been limited to the use of univariate analysis techniques. Current analysis methods lack the needed specificity for collagen and PGs. The aim of the present study was to evaluate the suitability of partial least squares regression (PLSR) and principal component regression (PCR) methods for the analysis of the PG content of AC. Multivariate regression models were compared with earlier used univariate methods and tested with a sample material consisting of healthy and enzymatically degraded steer AC. Chondroitinase ABC enzyme was used to increase the variation in PG content levels as compared to intact AC. Digital densitometric measurements of Safranin O –stained sections provided the reference for PG content. The results showed that multivariate regression models predict PG content of AC significantly better than earlier used absorbance spectrum (i.e. the area of carbohydrate region with or without amide I normalization) or second derivative spectrum univariate parameters. Increased molecular specificity favours the use of multivariate regression models, but they require more knowledge of chemometric analysis and extended laboratory resources for gathering reference data for establishing the models. When true molecular specificity is required, the multivariate models should be used.

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Section: Discussionmentioning

confidence: 86%

Fourier Transform Infrared Spectroscopic Imaging and Multivariate Regression for Prediction of Proteoglycan Content of Articular Cartilage

Rieppo

Jurvelin

et al. 2012

PLoS ONE

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“…While cartilage thickness was relatively constant during OA progression, 48 it was shown recently for the same sample set that in advanced OA the superficial zone became thinner. 47 It may even be that in some advanced OA samples the superficial zone has been totally worn out, and we have measured middle zone cells that are more circular. 13 On the other hand, the extracellular osmolarity of cartilage becomes hypotonic in OA.…”

Section: Discussionmentioning

confidence: 99%

Structural and Compositional Changes in Peri- and Extracellular Matrix of Osteoarthritic Cartilage Modulate Chondrocyte Morphology

et al. 2011

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It has not been shown how specific changes in composition and structure in the peri-and extracellular matrix (PCM and ECM) of human articular cartilage modulate cell morphology in different stages of osteoarthritis (OA). In the present study, cell morphology in the superficial tissue of normal, early OA and advanced OA human cartilage samples were measured from histological sections. Collagen and proteoglycan contents in the vicinity of chondrocytes were analyzed using Fourier transform infrared spectroscopy and digital densitometry. Determinants of the experimentally observed morphological changes of cells were studied using finite element analysis (FEA). From normal tissue to early OA, cell aspect ratio (height/width) remained constant (0.69 ± 0.11 and 0.69 ± 0.09, respectively). In advanced OA, cells became significantly (p < 0.05) more rounded (aspect ratio of 0.83 ± 0.13). Normalized collagen content in the PCM, i.e. collagen content in the PCM with respect to that in the ECM, was reduced significantly (p < 0.05) only in advanced OA. FEA indicated that reduced proteoglycan content and increased collagen fibrillation in the PCM and ECM, as well as reduced collagen content only in the PCM, primarily explained experimentally found changes in cell aspect ratio. Our results suggest that changes in composition and structure of the PCM and ECM in the superficial tissue of human articular cartilage modulate cell morphology differently in early and advanced OA.

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“…These results suggest a more prominent role for the collagen network than has been suggested by many articles, with key functional consequences. Finally, there is a possibility of overestimation of PG content with FTIR in samples with an inherently low PG content due to lack of specificity of this technique 33,45 . A similar issue has been reported for estimation of collagen content 15 .…”

Section: Discussionmentioning

confidence: 99%

Changes in mechanics and composition of human talar cartilage anlagen during fetal development

Mahmoodian

Leasure

Philip

et al. 2011

Osteoarthritis and Cartilage

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Objective Fetal cartilage anlage provides a framework for endochondral ossification and organization into articular cartilage. We previously reported differences between mechanical properties of talar cartilage anlagen and adult articular cartilage. However, the underlying development-associated changes remain to be established. Delineation of the normal evolvement of mechanical properties and its associated compositional basis provides insight into the natural mechanisms of cartilage maturation. Our goal was to address this issue. Materials and methods Human fetal cartilage anlagen were harvested from the tali of normal stillborn fetuses from 20 to 36 weeks of gestational age. Data obtained from stress relaxation experiments conducted under confined and unconfined compression configurations were processed to derive the compressive mechanical properties. The compressive mechanical properties were extracted from a linear fit to the equilibrium response in unconfined compression, and by using the nonlinear biphasic theory to fit to the experimental data from the confined compression experiment, both in stress-relaxation. The molecular composition was obtained using FTIR, and spatial maps of tissue contents per dry weight were created using FTIR imaging. Correlative and regression analyses were performed to identify relationships between the mechanical properties and age, compositional properties and age, and mechanical versus compositional parameters. Results All of the compositional quantities and the mechanical properties excluding the Poisson’s ratio changed with maturation. Stiffness increased by a factor of ~2.5 and permeability decreased by 20% over the period studied. Collagen content and degree of collagen integrity increased with age by ~3-fold, while the proteoglycan content decreased by 18%. Significant relations were found between the mechanical and compositional properties. Conclusion The mechanics of fetal talar cartilage is related to its composition, where the collagen and proteoglycan network play a prominent role. An understanding of the mechanisms of early cartilage maturation could provide a framework to guide tissue-engineering strategies.

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Specificity of Fourier Transform Infrared (FTIR) Microspectroscopy to Estimate Depth-Wise Proteoglycan Content in Normal and Osteoarthritic Human Articular Cartilage

Cited by 25 publications

References 20 publications

Fourier Transform Infrared Spectroscopic Imaging and Multivariate Regression for Prediction of Proteoglycan Content of Articular Cartilage

Fourier Transform Infrared Spectroscopic Imaging and Multivariate Regression for Prediction of Proteoglycan Content of Articular Cartilage

Structural and Compositional Changes in Peri- and Extracellular Matrix of Osteoarthritic Cartilage Modulate Chondrocyte Morphology

Changes in mechanics and composition of human talar cartilage anlagen during fetal development

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