title: Importance of Floating Chondrons in Cartilage Tissue Engineering.
abstract: BACKGROUND
  Dedifferentiation of chondrocytes remains a major problem for cartilage tissue engineering. Chondrocytes loss differentiated phenotype in in vitro culture that is undesired for repair strategies. The chondrocyte is surrounded by a pericellular matrix (PCM), together forming the chondron. PCM has a positive effect on the maintenance of chondrocyte phenotype during culture in comparison to uncovered chondrocyte. Studies suggest that the PCM influence on functional properties of the chondrocytes. However there is no study to show gene expression phenotype differences between round chondron and fibroblastic chondrocytes. We aimed to investigate the effect of pericellular matrix in maintaining of chondrogenic gene expression to solve dedifferentiation problem of chondrocyte.
  
  
  METHODS
  In this study enzymatically isolated chondrons were cultured for 7 days. Morphology of chondrons were assessed by microscopic examination. Chondrogenic gene expression of Sox9, aggrecan (AGG), cartilage oligomeric matrix protein (COMP), Link protein and chondro-osteogenic gene expression (Runx2, Col1, Col 10 and MMP13) of attached and float chondrons were assessed by real time RT PCR.
  
  
  RESULTS
  Microscopic observation showed that round shape of chondron observed at day 7 in floating chondrocytes. Gene expression results showed that attached chondrons significantly dedifferentiated by low gene expression of Sox9 and COMP and high MMP13 versus floating cells.
  
  
  CONCLUSIONS
  Our results showed that PCM of chondrocyte could restore differentiated state of chondrocytes at day 7. Using unattached form of chondron in cartilage tissue PCM in maintenance of chondrogenic gene expression engineering could be a novel method to solve dedifferentiation problem of chondrocyte.
authors.affiliation: Department of Anatomical Sciences, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Hajar
authors.initials: H
authors.lastname: Shafaei
authors.affiliation: Radiology Department, Sina Hospital, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Hajar
authors.initials: H
authors.lastname: Bagernezhad
authors.affiliation: Department of Anatomical Sciences, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Bagernajad
keywords: Cartilage tissue engineering; Chondron; Condrocyte; Dedifferentiation; PCM