title: Notochordal cells stimulate migration of cartilage end plate chondrocytes of the intervertebral disc in in vitro cell migration assays.
abstract: BACKGROUND
  It was recently demonstrated that the postnatal transition from a notochordal to a fibrocartilaginous nucleus pulposus (NP) is accomplished exogenously by chondrocytes migrating from hyaline cartilage end plates (CEs) into the ectopic notochordal NP region. Although our previous in vivo studies showed evidences for the migration of CE chondrocyte from hyaline CEs into the notochordal NP, it is unknown whether CE chondrocytes of the intervertebral disc (IVD) really have a motile property. In addition, the effect of notochordal cells on this property has not been elucidated.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to demonstrate whether CE chondrocytes of the IVD are capable of migration, and whether there is any biological link between notochordal cells and CE chondrocytes that may regulate the CE chondrocyte migration.
  
  
  METHODS
  In vitro cell migration assays were performed using rat IVDs.
  
  
  METHODS
  Notochordal cells and chondrocytes were obtained from the NP and CE tissues, respectively, and were cultured separately. The different numbers of notochordal cells and the supernatant (conditioned medium) that contained soluble factors produced by notochordal cells were used to demonstrate their effects on the migration of CE chondrocytes. Bovine serum albumin (BSA) and lysophosphatidic acid (LPA) were used as negative and positive controls, respectively.
  
  
  RESULTS
  Compared with BSA, LPA, notochordal cells (N=4x, 2x, 1x, and 0.5 x 10(5)), and its conditioned media (unconcentrated and fivefold concentrated) significantly increased migration of CE chondrocytes (p<.05 in all comparisons). Particularly, notochordal cells and its conditioned media increased migration in a number- and concentration-dependent manner, respectively.
  
  
  CONCLUSIONS
  This study demonstrates that CE chondrocytes of the IVD are capable of migration and that soluble factors produced by notochordal cells stimulate the migration. These results provide a plausible explanation to the question of why CE chondrocytes of the IVD migrate into the ectopic NP region during the natural transition from the notochordal to fibrocartilaginous NP.
authors.affiliation: Department of Orthopedic Surgery, St Mary's Hospital, The Catholic University of Korea, Seoul, Korea. kiwonk@lycos.co.kr
authors.forename: Ki-Won
authors.initials: KW
authors.lastname: Kim
authors.forename: Kee-Yong
authors.initials: KY
authors.lastname: Ha
authors.forename: Jun-Seok
authors.initials: JS
authors.lastname: Lee
authors.forename: Suk-Woo
authors.initials: SW
authors.lastname: Nam
authors.forename: Young-Kyun
authors.initials: YK
authors.lastname: Woo
authors.forename: Tae-Hong
authors.initials: TH
authors.lastname: Lim
authors.forename: Howard S
authors.initials: HS
authors.lastname: An
mesh_terms: D000818:Animals; D002356:Cartilage / Q000166:cytology; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology; D019902:Chondrocytes / Q000166:cytology* / Q000187:drug effects; D017077:Culture Media, Conditioned / Q000494:pharmacology; D006132:Growth Plate / Q000166:cytology / Q000196:embryology; D066298:In Vitro Techniques; D007403:Intervertebral Disc / Q000166:cytology* / Q000196:embryology; D008297:Male; D009672:Notochord / Q000166:cytology* / Q000196:embryology; D051381:Rats; D017208:Rats, Wistar; D012995:Solubility
chemical_list: D017077:Culture Media, Conditioned