title: Characteristic X-ray absorptiometry applied to the assessment of tissue-engineered cartilage development.
abstract: BACKGROUND
  Transmission and tomographic X-ray measurements are useful in assessing bone structures, but only a few studies have examined cartilage growth because of the poor contrast in conventional X-ray imaging.
  
  
  OBJECTIVE
  In this study, we attempted to use the linear attenuation coefficient (LAC) as a metric of tissue-engineered cartilage development, which would be useful in high-throughput screening of cartilage products.
  
  
  METHODS
  Assuming that the LAC is related to the amount of extracellular matrix (ECM) in terms of the density and its atomic components, we measured X-ray absorption through tissue-engineered cartilage constructs. Characteristic X-ray beams from a molybdenum microfocus X-ray tube were employed to avoid beam hardening. The correlation of the LAC with mechanical properties was analyzed for verification.
  
  
  RESULTS
  The LAC was higher for chondrocyte constructs and lower for fibroblast-dominant constructs and was consistent with the quantification of toluidine blue staining, which is a proof of ECM production. The LAC was positively correlated with the bending modulus but negatively correlated with the dynamic elastic modulus and stiffness, possibly because of the remaining scaffold.
  
  
  CONCLUSIONS
  The LAC has the potential to be used as a metric of development of tissue-engineered cartilage. However, the calcified regions should be excluded from analysis to avoid decreasing the correlation between the LAC and the amount of ECM.
authors.affiliation: Institute for Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Misawa
authors.affiliation: Institute for Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.
authors.forename: Naotaka
authors.initials: N
authors.lastname: Nitta
authors.affiliation: Institute for Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Shirasaki
authors.affiliation: Institute for Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Hayashi
authors.affiliation: Institute for Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Kosaka
authors.affiliation: Institute for Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Hyodo
authors.affiliation: Department of Radiological Science, Graduate School of Human Health Science, Tokyo Metropolitan University, Arakawa-ku, Tokyo, Japan.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Numano
authors.affiliation: Institute for Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Homma
authors.affiliation: Institute for Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Kuribayashi
authors.affiliation: Department of Cartilage and Bone Regeneration, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Fujihara
authors.affiliation: Department of Cartilage and Bone Regeneration, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Kazuto
authors.initials: K
authors.lastname: Hoshi
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods*; D002356:Cartilage / Q000166:cytology* / Q000502:physiology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology* / Q000502:physiology; D055119:Elastic Modulus; D006801:Humans; D023822:Tissue Engineering / Q000379:methods*
keywords: X-ray absorptiometry; characteristic X-ray; extra-cellular matrix; linear attenuation coefficient; tissue-engineered cartilage