title: Coculture between periosteal explants and articular chondrocytes induces expression of TGF-beta1 and collagen I.
abstract: OBJECTIVE
  Repair of focal articular cartilage lesions is usually performed by employing cell-based therapeutic strategies such as autologous chondrocyte implantation (ACI). The aim of this study was to determine whether periosteum exerts pro-chondrogenic effects on the transplanted cells beyond its biomechanical role in ACI.
  
  
  METHODS
  Micromass pellets of human articular chondrocytes were cocultured for up to 28 days with human periosteal explants either with physical contact or separated by a membrane allowing paracrine interactions only. Quantitative reverse transcription (RT)-PCR, ELISA, immunohistochemistry and collagen isolation were used to analyse the expression and secretion of TGF-beta1, collagens I and II and chondrogenic differentiation markers such as MIA (CD-RAP) and aggrecan.
  
  
  RESULTS
  TGF-beta1 gene expression was induced significantly in paracrine cocultures in periosteum, whereas it was repressed in physical contact cocultures. However, a higher TGF-beta1 secretion rate was observed in physical contact cocultures compared with periosteal monocultures. The expression of COL2A1, melanoma inhibitory activity (cartilage-derived retinoic acid-sensitive protein) [MIA (CD-RAP)] and aggrecan was mainly unaffected by culture conditions, whereas COL1A1 gene expression was increased in periosteal paracrine cocultures. Collagen I staining was induced in micromass pellets from paracrine cocultures, whereas it was repressed in chondrocytes from physical contact cocultures.
  
  
  CONCLUSIONS
  We found evidence for a bidirectional regulating system with paracrine signalling pathways between periosteum and articular chondrocytes. Stimulation of TGF-beta1 and COL1A1 gene expression in periosteal paracrine cocultures and the increased release of TGF-beta1 protein in physical contact conditions indicate an anabolic, and not merely chondrogenic micro-environment in this in vitro model for periosteal-based ACI.
authors: Department of Orthopaedic Surgery, University of Regensburg, ZMB/BioPark, Josef-Engert-Str. 9, 93053 Regensburg, Germany. susanne.graessel@klinik.uni-regensburg.de
authors: Susanne
authors: S
authors: Grässel
authors: Matthias
authors: M
authors: Rickert
authors: Alfred
authors: A
authors: Opolka
authors: Anja
authors: A
authors: Bosserhoff
authors: Peter
authors: P
authors: Angele
authors: Joachim
authors: J
authors: Grifka
authors: Sven
authors: S
authors: Anders
mesh_terms: D000368:Aged; D053674:Aggrecans / Q000378:metabolism; D002358:Cartilage, Articular / Q000166:cytology* / Q000378:metabolism; D002450:Cell Communication / Q000502:physiology; D019902:Chondrocytes / Q000378:metabolism*; D018920:Coculture Techniques; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism*; D024043:Collagen Type II / Q000378:metabolism; D004396:Coloring Agents; D015870:Gene Expression; D006801:Humans; D008875:Middle Aged; D019899:Paracrine Communication / Q000502:physiology; D010521:Periosteum / Q000166:cytology*; D010619:Phenazines; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism*
chemical_list: D053674:Aggrecans; D024042:Collagen Type I; D024043:Collagen Type II; D004396:Coloring Agents; D010619:Phenazines; D053773:Transforming Growth Factor beta1; C009195:safranine T