title: Persistent stromal fibroblast activation is present in chronic tendinopathy.
abstract: BACKGROUND
  Growing evidence supports a key role for inflammation in the onset and progression of tendinopathy. However, the effect of the inflammatory infiltrate on tendon cells is poorly understood.
  
  
  METHODS
  We investigated stromal fibroblast activation signatures in tissues and cells from patients with tendinopathy. Diseased tendons were collected from well-phenotyped patient cohorts with supraspinatus tendinopathy before and after sub-acromial decompression treatment. Healthy tendons were collected from patients undergoing shoulder stabilisation or anterior cruciate ligament repair. Stromal fibroblast activation markers including podoplanin (PDPN), CD106 (VCAM-1) and CD248 were investigated by immunostaining, flow cytometry and RT-qPCR.
  
  
  RESULTS
  PDPN, CD248 and CD106 were increased in diseased compared to healthy tendon tissues. This stromal fibroblast activation signature persisted in tendon biopsies in patients at 2-4 years post treatment. PDPN, CD248 and CD106 were increased in diseased compared to healthy tendon cells. IL-1β treatment induced PDPN and CD106 but not CD248. IL-1β treatment induced NF-κB target genes in healthy cells, which gradually declined following replacement with cytokine-free medium, whilst PDPN and CD106 remained above pre-stimulated levels. IL-1β-treated diseased cells had more profound induction of PDPN and CD106 and sustained expression of IL6 and IL8 mRNA compared to IL-1β-treated healthy cells.
  
  
  CONCLUSIONS
  We conclude that stromal fibroblast activation markers are increased and persist in diseased compared to healthy tendon tissues and cells. Diseased tendon cells have distinct stromal fibroblast populations. IL-1β treatment induced persistent stromal fibroblast activation which was more profound in diseased cells. Persistent stromal fibroblast activation may be implicated in the development of chronic inflammation and recurrent tendinopathy. Targeting this stromal fibroblast activation signature is a potential therapeutic strategy.
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Nuffield Orthopaedic Centre, Headington, OX3 7LD, UK. stephanie.dakin@ndorms.ox.ac.uk.
authors.forename: Stephanie G
authors.initials: SG
authors.lastname: Dakin
authors.affiliation: Rheumatology Research Group Institute of Inflammation and Ageing, University of Birmingham research laboratories, Queen Elizabeth Hospital, Birmingham, UK.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Buckley
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Nuffield Orthopaedic Centre, Headington, OX3 7LD, UK.
authors.forename: Mohammad Hussein
authors.initials: MH
authors.lastname: Al-Mossawi
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Nuffield Orthopaedic Centre, Headington, OX3 7LD, UK.
authors.forename: Robert
authors.initials: R
authors.lastname: Hedley
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Nuffield Orthopaedic Centre, Headington, OX3 7LD, UK.|Faculty of Health & Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK.
authors.forename: Fernando O
authors.initials: FO
authors.lastname: Martinez
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Nuffield Orthopaedic Centre, Headington, OX3 7LD, UK.
authors.forename: Kim
authors.initials: K
authors.lastname: Wheway
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Nuffield Orthopaedic Centre, Headington, OX3 7LD, UK.
authors.forename: Bridget
authors.initials: B
authors.lastname: Watkins
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Nuffield Orthopaedic Centre, Headington, OX3 7LD, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Carr
mesh_terms: D000328:Adult; D000368:Aged; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D002908:Chronic Disease; D005260:Female; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D053583:Interleukin-1beta / Q000494:pharmacology; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D008875:Middle Aged; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017154:Stromal Cells / Q000166:cytology*; D052256:Tendinopathy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D013710:Tendons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D019010:Vascular Cell Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism; D055815:Young Adult; D000098853:Podoplanin
chemical_list: D015703:Antigens, CD; D000951:Antigens, Neoplasm; D053583:Interleukin-1beta; D008562:Membrane Glycoproteins; D019010:Vascular Cell Adhesion Molecule-1; C078203:CD248 protein, human; C117468:PDPN protein, human; D000098853:Podoplanin
keywords: Inflammation; Stromal fibroblast; Tendinopathy; Tendon