title: The intervertebral disc contains intrinsic circadian clocks that are regulated by age and cytokines and linked to degeneration.
abstract: OBJECTIVE
  The circadian clocks are internal timing mechanisms that drive ∼24-hour rhythms in a tissue-specific manner. Many aspects of the physiology of the intervertebral disc (IVD) show clear diurnal rhythms. However, it is unknown whether IVD tissue contains functional circadian clocks and if so, how their dysregulation is implicated in IVD degeneration.
  
  
  METHODS
  Clock gene dynamics in ex vivo IVD explants (from PER2:: luciferase (LUC) reporter mice) and human disc cells (transduced with lentivirus containingPer2::luc reporters) were monitored in real time by bioluminescence photon counting and imaging. Temporal gene expression changes were studied by RNAseq and quantitative reverse transcription (qRT)-PCR. IVD pathology was evaluated by histology in a mouse model with tissue-specific deletion of the core clock geneBmal1.
  
  
  RESULTS
  Here we show the existence of the circadian rhythm in mouse IVD tissue and human disc cells. This rhythm is dampened with ageing in mice and can be abolished by treatment with interleukin-1β but not tumour necrosis factor α. Time-series RNAseq revealed 607 genes with 24-hour patterns of expression representing several essential pathways in IVD physiology. Mice with conditional knockout ofBmal1in their disc cells demonstrated age-related degeneration of IVDs.
  
  
  CONCLUSIONS
  We have established autonomous circadian clocks in mouse and human IVD cells which respond to age and cytokines, and control key pathways involved in the homeostasis of IVDs. Genetic disruption to the mouse IVD molecular clock predisposes to IVD degeneration. These results support the concept that disruptions to circadian rhythms may be a risk factor for degenerative IVD disease and low back pain.
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, UK.|Wellcome Trust Centre for Cell Matrix Research, University of Manchester, Manchester, UK.
authors.forename: Michal
authors.initials: M
authors.lastname: Dudek
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, UK.|Wellcome Trust Centre for Cell Matrix Research, University of Manchester, Manchester, UK.
authors.forename: Nan
authors.initials: N
authors.lastname: Yang
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, UK.|Wellcome Trust Centre for Cell Matrix Research, University of Manchester, Manchester, UK.
authors.forename: Jayalath Pd
authors.initials: JP
authors.lastname: Ruckshanthi
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, UK.|Wellcome Trust Centre for Cell Matrix Research, University of Manchester, Manchester, UK.
authors.forename: Jack
authors.initials: J
authors.lastname: Williams
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, UK.
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Borysiewicz
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, UK.
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, UK.
authors.forename: Antony
authors.initials: A
authors.lastname: Adamson
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, UK.
authors.forename: Jian
authors.initials: J
authors.lastname: Li
authors.affiliation: Murdoch Children's Research Institute, Parkville, Victoria, Australia.
authors.forename: John F
authors.initials: JF
authors.lastname: Bateman
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, UK.
authors.forename: Michael R
authors.initials: MR
authors.lastname: White
authors.affiliation: Wellcome Trust Centre for Cell Matrix Research, University of Manchester, Manchester, UK.
authors.forename: Raymond P
authors.initials: RP
authors.lastname: Boot-Handford
authors.affiliation: Faculty of Medical and Human Sciences, Centre for Tissue Injury and Repair, University of Manchester, Manchester, UK.|NIHR Manchester Musculoskeletal Biomedical Research Unit, Manchester Academic Health Science Centre, Manchester, UK.
authors.forename: Judith A
authors.initials: JA
authors.lastname: Hoyland
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, UK.|Wellcome Trust Centre for Cell Matrix Research, University of Manchester, Manchester, UK.
authors.forename: Qing-Jun
authors.initials: QJ
authors.lastname: Meng
mesh_terms: D056930:ARNTL Transcription Factors / Q000032:analysis / Q000235:genetics*; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D000818:Animals; D056926:CLOCK Proteins / Q000032:analysis; D002478:Cells, Cultured; D057906:Circadian Clocks / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D002940:Circadian Rhythm / Q000187:drug effects / Q000235:genetics; D006801:Humans; D053583:Interleukin-1beta / Q000494:pharmacology; D007403:Intervertebral Disc / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D055959:Intervertebral Disc Degeneration / Q000235:genetics / Q000503:physiopathology*; D051379:Mice; D018345:Mice, Knockout; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D000070614:Nucleus Pulposus / Q000737:chemistry / Q000166:cytology / Q000502:physiology; D056950:Period Circadian Proteins / Q000235:genetics*; D015398:Signal Transduction; D013696:Temperature; D046509:Tissue Culture Techniques; D059467:Transcriptome; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D056930:ARNTL Transcription Factors; C538960:BMAL1 protein, human; C538961:Bmal1 protein, mouse; D053583:Interleukin-1beta; D016328:NF-kappa B; C421902:PER2 protein, human; C513312:Per2 protein, mouse; D056950:Period Circadian Proteins; D014409:Tumor Necrosis Factor-alpha; D056926:CLOCK Proteins; C538943:CLOCK protein, human; C538944:Clock protein, mouse
keywords: Arthritis; Chondrocytes; Cytokines; Low Back Pain