title: The Role of Prostaglandins and COX-Enzymes in Chondrogenic Differentiation of ATDC5 Progenitor Cells.
abstract: OBJECTIVE
  NSAIDs are used to relieve pain and decrease inflammation by inhibition of cyclooxygenase (COX)-catalyzed prostaglandin (PG) synthesis. PGs are fatty acid mediators involved in cartilage homeostasis, however the action of their synthesizing COX-enzymes in cartilage differentiation is not well understood. In this study we hypothesized that COX-1 and COX-2 have differential roles in chondrogenic differentiation.
  
  
  METHODS
  ATDC5 cells were differentiated in the presence of COX-1 (SC-560, Mofezolac) or COX-2 (NS398, Celecoxib) specific inhibitors. Specificity of the NSAIDs and inhibition of specific prostaglandin levels were determined by EIA. Prostaglandins were added during the differentiation process. Chondrogenic outcome was determined by gene- and protein expression analyses.
  
  
  RESULTS
  Inhibition of COX-1 prevented Col2a1 and Col10a1 expression. Inhibition of COX-2 resulted in decreased Col10a1 expression, while Col2a1 remained unaffected. To explain this difference expression patterns of both COX-enzymes as well as specific prostaglandin concentrations were determined. Both COX-enzymes are upregulated during late chondrogenic differentiation, whereas only COX-2 is briefly expressed also early in differentiation. PGD2 and PGE2 followed the COX-2 expression pattern, whereas PGF2α and TXA2 levels remained low. Furthermore, COX inhibition resulted in decreased levels of all tested PGs, except for PGD2 and PGF2α in the COX-1 inhibited condition. Addition of PGE2 and PGF2α resulted in increased expression of chondrogenic markers, whereas TXA2 increased expression of hypertrophic markers.
  
  
  CONCLUSIONS
  Our findings point towards a differential role for COX-enzymes and PG-production in chondrogenic differentiation of ATDC5 cells. Ongoing research is focusing on further elucidating the functional partition of cyclooxygenases and specific prostaglandin production.
authors.affiliation: Department of Orthopaedic Surgery, Caphri School for Public Health and Primary Care, Maastricht University Medical Centre, Maastricht, the Netherlands.
authors.forename: Marjolein M J
authors.initials: MM
authors.lastname: Caron
authors.affiliation: Department of Orthopaedic Surgery, Caphri School for Public Health and Primary Care, Maastricht University Medical Centre, Maastricht, the Netherlands.
authors.forename: Pieter J
authors.initials: PJ
authors.lastname: Emans
authors.affiliation: Department of Orthopaedic Surgery, Caphri School for Public Health and Primary Care, Maastricht University Medical Centre, Maastricht, the Netherlands.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Sanen
authors.affiliation: Department of Orthopaedic Surgery, Caphri School for Public Health and Primary Care, Maastricht University Medical Centre, Maastricht, the Netherlands.
authors.forename: Don A M
authors.initials: DA
authors.lastname: Surtel
authors.affiliation: Department of Orthopaedic Surgery, Caphri School for Public Health and Primary Care, Maastricht University Medical Centre, Maastricht, the Netherlands.
authors.forename: Andy
authors.initials: A
authors.lastname: Cremers
authors.affiliation: Department of Orthopaedic Surgery, Caphri School for Public Health and Primary Care, Maastricht University Medical Centre, Maastricht, the Netherlands.
authors.forename: Daan
authors.initials: D
authors.lastname: Ophelders
authors.affiliation: Department of Orthopaedic Surgery, Caphri School for Public Health and Primary Care, Maastricht University Medical Centre, Maastricht, the Netherlands.
authors.forename: Lodewijk W
authors.initials: LW
authors.lastname: van Rhijn
authors.affiliation: Department of Orthopaedic Surgery, Caphri School for Public Health and Primary Care, Maastricht University Medical Centre, Maastricht, the Netherlands.
authors.forename: Tim J M
authors.initials: TJ
authors.lastname: Welting
mesh_terms: D000818:Animals; D002356:Cartilage / Q000737:chemistry*; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D051545:Cyclooxygenase 1 / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D051379:Mice; D011453:Prostaglandins / Q000502:physiology*; D013234:Stem Cells / Q000166:cytology*
chemical_list: D011453:Prostaglandins; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2