title: Gene expression during redifferentiation of human articular chondrocytes.
abstract: OBJECTIVE
  The aim of the present study was to investigate gene expression during the in vitro redifferentiation process of human articular chondrocytes isolated from clinical samples from patient undergoing an autologous chondrocyte transplantation therapy (ACT).
  
  
  METHODS
  Monolayer (ML) expanded human articular chondrocytes from four donors were cultured in a 3D pellet model and the redifferentiation was investigated by biochemistry, histology, immunohistochemistry and microarray analysis.
  
  
  RESULTS
  The culture expanded chondrocytes redifferentiated in the pellet model as seen by an increase in collagen type II immunoreactivity between day 7 and 14. The gene expression from ML to pellet at day 7 included an increase in cartilage matrix proteins like collagen type XI, tenascin C, dermatopontin, COMP and fibronectin. The late phase consisted of a strong downregulation of extracellular signal-regulated protein kinase (ERK-1) and an upregulation of p38 kinase and SOX-9, suggesting that the late phase mimicked parts of the signaling processes involved in the early chondrogenesis in limb bud cells. Other genes, which indicated a transition from proliferation to tissue formation, were the downregulated cell cycle genes GSPT1 and the upregulated growth-arrest-specific protein (gas). The maturation of the pellets included no signs of hypertrophy or apoptosis as seen by downregulation of collagen type X, Matrix Gla protein and increased expression of caspase 3.
  
  
  CONCLUSIONS
  Our data show that human articular chondrocytes taken from surplus cells of patient undergoing ACT treatment and expanded in ML, redifferentiate and form cartilage like matrix in vitro and that this dynamic process involves genes known to be expressed in early chondrogenesis.
authors.affiliation: Department of Clinical Chemistry and Transfusion Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden. tommi.tallheden@medic.gu.se
authors.forename: Tommi
authors.initials: T
authors.lastname: Tallheden
authors.forename: Camilla
authors.initials: C
authors.lastname: Karlsson
authors.forename: Andreas
authors.initials: A
authors.lastname: Brunner
authors.forename: Josefine
authors.initials: J
authors.lastname: Van Der Lee
authors.forename: Rupert
authors.initials: R
authors.lastname: Hagg
authors.forename: Roberto
authors.initials: R
authors.lastname: Tommasini
authors.forename: Anders
authors.initials: A
authors.lastname: Lindahl
mesh_terms: D000328:Adult; D002358:Cartilage, Articular / Q000473:pathology / Q000503:physiopathology*; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000473:pathology / Q000502:physiology* / Q000637:transplantation; D003094:Collagen / Q000032:analysis; D015870:Gene Expression / Q000235:genetics / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods
chemical_list: D003094:Collagen