title: Particulate cartilage under bioreactor-induced compression and shear.
abstract: OBJECTIVE
  Our aim was to explore the effect of varying in vitro culture conditions on general chondrogenesis of minced cartilage (MC) fragments.
  
  
  METHODS
  Minced, fibrin-associated, bovine articular cartilage fragments were cultured in vitro within polyurethane scaffold rings. Constructs were maintained either free swelling for two or four weeks (control), underwent direct mechanical knee-joint-specific bioreactor-induced dynamic compression and shear, or they were maintained free swelling for two weeks followed by two weeks of bioreactor stimulation. Samples were collected for glycosaminoglycan (GAG)/DNA quantification; collagen type I, collagen type II, aggrecan, cartilage oligomeric matrix protein (COMP), proteoglycan-4 (PRG-4) messenger RNA (mRNA) analysis; histology and immunohistochemistry.
  
  
  RESULTS
  Cellular outgrowth and neomatrix formation was successfully accomplished among all groups. GAG/DNA and collagen type I mRNA were not different between groups; chondrogenic genes collagen type II, aggrecan and COMP revealed a significant downregulation among free-swelling constructs over time (week two through week four). Mechanical loading was able to maintain chondrogenic expression with significantly stronger expression at long-term time points (four weeks) in comparison with four-week control. Histology and immunohistochemistry revealed that bioreactor culture induced stronger cellular outgrowth than free-swelling constructs. However, weaker collagen type II and aggrecan expression with an increased collagen type I expression was noted among this outgrowth neotissue.
  
  
  CONCLUSIONS
  The method of MC culture is feasible under in vitro free-swelling and dynamic loading conditions, simulating in vivo posttransplantation. Mechanical stimulation significantly provokes cellular outgrowth and long-term chondrogenic maturation at the mRNA level, whereas histology depicts immature neotissue where typical cartilage matrix is expected.
authors.affiliation: Department of Orthopaedic Surgery, Chinese PLA General Hospital, 100853, Beijing, People's Republic of China.
authors.forename: Ning
authors.initials: N
authors.lastname: Wang
authors.forename: Sibylle
authors.initials: S
authors.lastname: Grad
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Stoddart
authors.forename: Philipp
authors.initials: P
authors.lastname: Niemeyer
authors.forename: Kilian
authors.initials: K
authors.lastname: Reising
authors.forename: Hagen
authors.initials: H
authors.lastname: Schmal
authors.forename: Norbert P
authors.initials: NP
authors.lastname: Südkamp
authors.forename: Mauro
authors.initials: M
authors.lastname: Alini
authors.forename: Gian M
authors.initials: GM
authors.lastname: Salzmann
mesh_terms: D000818:Animals; D019149:Bioreactors; D002356:Cartilage / Q000166:cytology*; D002417:Cattle; D020219:Chondrogenesis; D011312:Pressure; D013314:Stress, Mechanical; D046509:Tissue Culture Techniques