title: Inflammatory cytokines induce fibrosis and ossification of human ligamentum flavum cells.
abstract: METHODS
  In vitro experiment using degenerated human ligamentum flavum (LF) and various inflammatory cytokines.
  
  
  OBJECTIVE
  To examine the effect of inflammatory cytokines on LF cells and to identify their roles in the pathogenesis of LF hypertrophy and ossification.
  
  
  BACKGROUND
  Spinal stenosis is caused, in part, by hypertrophy and ossification of the LF, which are induced by the degenerative processes (ie, increased collagen synthesis and chondroid metaplasia) of ligament fibroblasts. Degenerated intervertebral disk spontaneously produces inflammatory cytokines, which might affect the adjacent LF through local milieu of the spinal canal.
  
  
  METHODS
  The interlaminar portion of the LF was collected during surgical spinal procedures in 15 patients (age range, 49-78 y) with lumbar spinal stenosis. LF fibroblasts were isolated by enzymatic digestion of LF tissue. LF cell cultures were treated with various inflammatory cytokines: interleukin (IL)-1α, IL-6, tumor necrosis factor-α (TNF-α), prostaglandin E2 (PGE2), and nitric oxide (NO). Cytotoxicity was analyzed by MTT assays. DNA synthesis was measured with H-thymidine incorporation, and mRNA expression of types I, III, V, and XI collagen and osteocalcin were performed by reverse transcription-polymerase chain reaction. Histochemical stains such as Von Kossa were also performed to detect bone nodule formation.
  
  
  RESULTS
  There was no cytotoxicity in the LF cells treated with each cytokine. There were significant increases in DNA synthesis and upregulated mRNA expression of types I, V, XI collagen and osteocalcin in LF cultures treated with various cytokines. LF cultures treated with IL-6, TNF-α, PGE2, and NO showed positive Von Kossa staining, indicating bone nodule formation from LF cells.
  
  
  CONCLUSIONS
  Inflammatory cytokines (IL-6, TNF-α, PGE2, and NO) seem to play a crucial role in hypertrophy and ossification of LF. Degenerated, herniated intervertebral disks, and facet arthrosis may influence LF through inflammatory cytokines and cause hypertrophy and ossification of LF.
authors: Department of Orthopaedic Surgery, Yonsei University College of Medicine, Brain Korea 21 Project for Medical Science, Seoul, Korea.
authors: Jin-Oh
authors: JO
authors: Park
authors: Byung Ho
authors: BH
authors: Lee
authors: Young-Mi
authors: YM
authors: Kang
authors: Tae-Hwan
authors: TH
authors: Kim
authors: Ji Young
authors: JY
authors: Yoon
authors: Hyang
authors: H
authors: Kim
authors: Un-Hye
authors: UH
authors: Kwon
authors: Kwang-Il
authors: KI
authors: Lee
authors: Hwan-Mo
authors: HM
authors: Lee
authors: Seong-Hwan
authors: SH
authors: Moon
mesh_terms: D000368:Aged; D016207:Cytokines / Q000276:immunology*; D005260:Female; D006801:Humans; D007155:Immunologic Factors / Q000276:immunology*; D017843:Ligamentum Flavum / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009999:Ossification, Heterotopic / Q000276:immunology*; D013166:Spondylitis / Q000276:immunology*; D014018:Tissue Distribution
chemical_list: D016207:Cytokines; D007155:Immunologic Factors