title: The efficacy of Link N as a mediator of repair in a rabbit model of intervertebral disc degeneration.
abstract: BACKGROUND
  Intervertebral disc (IVD) degeneration is associated with proteolytic degradation of the extracellular matrix, and its repair requires both the production of extracellular matrix and the downregulation of proteinase activity. These properties are associated with several growth factors. However, the use of growth factors in clinical practice is limited by their high cost. This cost can be circumvented using synthetic peptides, such as Link N, which can stimulate the synthesis of proteoglycan and collagen by IVD cells in vitro. The purpose of the present study was to evaluate the effect of Link N in vivo in a rabbit model of IVD degeneration.
  
  
  METHODS
  New Zealand white rabbits received annular puncture in two lumbar discs. Two weeks after puncture, both punctured discs of each rabbit were injected with either Link N or saline. After 2 weeks, nine rabbits were euthanized and the annulus fibrosus (AF) and nucleus pulposus (NP) of Link N-injected and saline-injected IVDs were removed and used to prepare total RNA. Following reverse transcription, quantitative PCR was performed for aggrecan, COL2A1, COL1A1, ADAMTS-4, ADAMTS-5 and MMP-3. After 12 weeks, 19 rabbits were euthanized and the injected IVDs were removed for biochemical and histological analysis. Proteinase K digests were analyzed for DNA and sulfated glycosaminoglycan content. Disc height was monitored radiographically biweekly.
  
  
  RESULTS
  Following needle puncture, disc height decreased by about 25% over 2 weeks, and was partially restored by Link N injection. Puncture of the IVD resulted in a trend towards decreased proteoglycan content in both the NP and AF, and a trend towards partial restoration following Link N injection, although under the time course used this did not achieve statistical significance. Link N did not alter the DNA content of the discs. Link N injection led to a significant increase in aggrecan gene expression and a significant decrease in proteinase gene expression in both the NP and AF, when compared with saline alone.
  
  
  CONCLUSIONS
  When administered to the degenerate disc in vivo, Link N stimulated aggrecan gene expression and downregulated metalloproteinase expression, and there was a trend towards increased proteoglycan content of the disc, in both the NP and AF. These are features needed for any agent designed to stimulate disc repair. In principle, therefore, Link N supplementation could be an option for treating disc degeneration.
authors.affiliation: Division of Orthopaedic Surgery, McGill University, 1650 Cedar Avenue, Montreal, QC, Canada, H3G 1A4. fmwale@ldi.jgh.mcgill.ca
authors.forename: Fackson
authors.initials: F
authors.lastname: Mwale
authors.forename: Koichi
authors.initials: K
authors.lastname: Masuda
authors.forename: Rajeswari
authors.initials: R
authors.lastname: Pichika
authors.forename: Laura M
authors.initials: LM
authors.lastname: Epure
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Yoshikawa
authors.forename: Aseem
authors.initials: A
authors.lastname: Hemmad
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Roughley
authors.forename: John
authors.initials: J
authors.lastname: Antoniou
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005109:Extracellular Matrix / Q000187:drug effects*; D016326:Extracellular Matrix Proteins / Q000008:administration & dosage*; D007270:Injections, Intra-Articular; D055959:Intervertebral Disc Degeneration / Q000188:drug therapy* / Q000473:pathology; D010455:Peptides / Q000008:administration & dosage; D011509:Proteoglycans / Q000008:administration & dosage*; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000099249:Proteoglycan Link Protein
chemical_list: D016326:Extracellular Matrix Proteins; D010455:Peptides; D011509:Proteoglycans; D000099249:Proteoglycan Link Protein