title: Characterization of miRNA expression in human degenerative lumbar disks.
abstract: BACKGROUND
  microRNAs (miRNAs) are short ∼22 nucleotide RNA sequences that regulate messengerRNA translation. miRNAs have shown to play a role in synthesis of inflammatory mediators. Since inflammation play a role in intervertebral disk (IVD) degeneration, the objective was to isolate miRNA from human lumbar intervertebral disks and subsequently characterize the difference in miRNA expression between the annulus fibrosus (AF) and nucleus pulposus (NP).
  
  
  METHODS
  Fourteen patients undergoing anterior interbody fusion for degenerative disk disease of the lumbar spine were included. During surgery biopsies from the intervertebral disks were obtained and immediately placed in RNAlater. The RNAlater was decanted and the samples frozen at -80˚C until RNA extraction. This was performed using the Trizol method. Global miRNA expression analysis was performed using the Affymetrix GeneChip® miRNA array.
  
  
  RESULTS
  We developed a method allowing the extraction of miRNA from human intervertebral disks usually yielding 1-4 µg of total RNA pr. 100 mg of disk. Twenty-seven miRNAs had a higher expression in the AF and 10 had the highest expression in the NP. Among the top 15 signaling pathways most likely to be controlled by these miRNAs were the transforming growth factor β (TGFβ), platelet-derived growth factor (PDGF), insulin-like growth factor (IGF) epidermal growth factor (EGF), and actin cytoskeletal pathway.
  
  
  CONCLUSIONS
  We have demonstrated the presence of miRNA in the human IVD. The miRNA expression differs from muscle tissue and there are differences between the miRNA expressed in the NP and AF. The miRNAs identified control signaling pathways important for maintenance of the IVD. Future studies may determine the importance of miRNA in the development of IVD disease.
authors.affiliation: Genomic Medicine, Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark. ohrtnissen@gmail.com
authors.forename: Søren
authors.initials: S
authors.lastname: Ohrt-Nissen
authors.forename: Kristina B V
authors.initials: KB
authors.lastname: Døssing
authors.forename: Maria
authors.initials: M
authors.lastname: Rossing
authors.forename: Christel
authors.initials: C
authors.lastname: Lajer
authors.forename: Jonas
authors.initials: J
authors.lastname: Vikeså
authors.forename: Finn Cilius
authors.initials: FC
authors.lastname: Nielsen
authors.forename: Lennart
authors.initials: L
authors.lastname: Friis-Hansen
authors.forename: Benny
authors.initials: B
authors.lastname: Dahl
mesh_terms: D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D017403:In Situ Hybridization; D007403:Intervertebral Disc / Q000473:pathology*; D055959:Intervertebral Disc Degeneration / Q000235:genetics*; D008159:Lumbar Vertebrae / Q000473:pathology*; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D009132:Muscles / Q000378:metabolism / Q000473:pathology; D016133:Polymerase Chain Reaction; D025341:Principal Component Analysis; D015203:Reproducibility of Results; D015398:Signal Transduction / Q000235:genetics
chemical_list: D035683:MicroRNAs