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Clustering of infrared spectra reveals histological zones in intact articular cartilage

Kobrina, Yevgeniya; Rieppo, Lassi; Saarakkala, Simo; Jurvelin, Jukka S. and Isaksson, Hanna LU (2012) In Osteoarthritis and Cartilage 20(5). p.460-468
Abstract
Objective: Articular cartilage (AC) exhibits specific zonal structure that follows the organization of collagen network and concentration of tissue constituents. The aim of this study was to investigate the potential of unsupervised clustering analysis applied to Fourier transform infrared (FIR) microspectroscopy to detect depth-dependent structural and compositional differences in intact AC. Method: Seven rabbit and eight bovine intact patellae AC samples were imaged using FTIR microspectroscopy and normalized raw spectra were clustered using the fuzzy C-means algorithm. Differences in mean spectra of clusters were investigated by quantitative estimation of collagen and proteoglycan (PG) contents, as well as by careful visual... (More)
Objective: Articular cartilage (AC) exhibits specific zonal structure that follows the organization of collagen network and concentration of tissue constituents. The aim of this study was to investigate the potential of unsupervised clustering analysis applied to Fourier transform infrared (FIR) microspectroscopy to detect depth-dependent structural and compositional differences in intact AC. Method: Seven rabbit and eight bovine intact patellae AC samples were imaged using FTIR microspectroscopy and normalized raw spectra were clustered using the fuzzy C-means algorithm. Differences in mean spectra of clusters were investigated by quantitative estimation of collagen and proteoglycan (PG) contents, as well as by careful visual investigation of locations of spectral changes. Results: Clustering revealed the typical layered structure of AC in both species. However, more distinct clusters were found for rabbit samples, whereas bovine AC showed more complex layered structure. In both species, clustering structure corresponded with that in polarized light microscopic (PLM) images; however, some differences were also observed. Spectral differences between clusters were identified at the same spectral locations for both species. Estimated PG/collagen ratio decreased significantly from superficial to middle or deep zones, which might explain the difference in clustering results compared to PLM. Conclusion: FTIR microspectroscopy in combination with cluster analysis allows detailed examination of spatial changes in AC. As far as we know, no previous single technique could reveal a layered structure of AC without any a priori information. (C) 2012 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Articular cartilage, Histological zones, Fourier transform infrared, spectroscopy, Cluster analysis
in
Osteoarthritis and Cartilage
volume
20
issue
5
pages
460 - 468
publisher
Elsevier
external identifiers
  • wos:000303297100017
  • scopus:84859427323
ISSN
1063-4584
DOI
10.1016/j.joca.2012.01.014
language
English
LU publication?
yes
id
9f5d611e-ae2d-4f31-9960-ae1b81b0a1d0 (old id 2563298)
date added to LUP
2012-05-30 13:42:38
date last changed
2017-05-21 03:05:38
@article{9f5d611e-ae2d-4f31-9960-ae1b81b0a1d0,
  abstract     = {Objective: Articular cartilage (AC) exhibits specific zonal structure that follows the organization of collagen network and concentration of tissue constituents. The aim of this study was to investigate the potential of unsupervised clustering analysis applied to Fourier transform infrared (FIR) microspectroscopy to detect depth-dependent structural and compositional differences in intact AC. Method: Seven rabbit and eight bovine intact patellae AC samples were imaged using FTIR microspectroscopy and normalized raw spectra were clustered using the fuzzy C-means algorithm. Differences in mean spectra of clusters were investigated by quantitative estimation of collagen and proteoglycan (PG) contents, as well as by careful visual investigation of locations of spectral changes. Results: Clustering revealed the typical layered structure of AC in both species. However, more distinct clusters were found for rabbit samples, whereas bovine AC showed more complex layered structure. In both species, clustering structure corresponded with that in polarized light microscopic (PLM) images; however, some differences were also observed. Spectral differences between clusters were identified at the same spectral locations for both species. Estimated PG/collagen ratio decreased significantly from superficial to middle or deep zones, which might explain the difference in clustering results compared to PLM. Conclusion: FTIR microspectroscopy in combination with cluster analysis allows detailed examination of spatial changes in AC. As far as we know, no previous single technique could reveal a layered structure of AC without any a priori information. (C) 2012 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.},
  author       = {Kobrina, Yevgeniya and Rieppo, Lassi and Saarakkala, Simo and Jurvelin, Jukka S. and Isaksson, Hanna},
  issn         = {1063-4584},
  keyword      = {Articular cartilage,Histological zones,Fourier transform infrared,spectroscopy,Cluster analysis},
  language     = {eng},
  number       = {5},
  pages        = {460--468},
  publisher    = {Elsevier},
  series       = {Osteoarthritis and Cartilage},
  title        = {Clustering of infrared spectra reveals histological zones in intact articular cartilage},
  url          = {http://dx.doi.org/10.1016/j.joca.2012.01.014},
  volume       = {20},
  year         = {2012},
}