title: Investigation of keratinocyte regulation of collagen I synthesis by dermal fibroblasts in a simple in vitro model.
abstract: BACKGROUND
  Hypertrophic scarring and skin graft contracture are major causes of morbidity after burn injuries. A prominent feature is excessive fibroplasia with accumulation of increased fibrillar collagen relative to normal scar tissue. The application of split-thickness skin grafts or cultured epithelial autografts to burn wounds is known to reduce scarring and contraction.
  
  
  OBJECTIVE
  To investigate further how the keratinocyte influences underlying fibroblast behaviour by examining the influence of keratinocytes on fibroblast collagen synthesis, using a new assay for collagen synthesis never previously applied to skin cell biology.
  
  
  METHODS
  We investigated the influence of the keratinocyte on fibroblast synthesis of type I collagen using an immunoassay for the aminoterminal propeptide of type I collagen (P1NP) in conditioned medium from monocultures and cocultures of keratinocytes and fibroblasts over 14 days. The importance of the physical presence of the keratinocyte was investigated by comparing cocultures of keratinocytes and fibroblasts against fibroblast monocultures with keratinocyte-conditioned medium. Pharmacological agents known to promote fibroblast proliferation [basic fibroblast growth factor (bFGF)], keratinocyte proliferation [insulin-like growth factor (IGF)-1], modify scarring in vivo[tumour necrosis factor (TNF)-alpha] or modify collagen biochemistry [putrescine, estrone, estradiol and beta-aminopropionitrile (beta-APN)] were then investigated for their effect on collagen synthesis in fibroblasts and in keratinocyte/fibroblast cocultures.
  
  
  RESULTS
  Keratinocytes in coculture with fibroblasts, and keratinocyte-conditioned medium, both reduced fibroblast P1NP synthesis. Of the pharmacological agents investigated, bFGF, IGF-1, TNF-alpha and beta-APN all increased collagen synthesis both in monocultures of fibroblasts and in cocultures of keratinocytes and fibroblasts.
  
  
  CONCLUSIONS
  Fibroblast collagen synthesis appears to be downregulated by keratinocyte-derived cytokines. Fibroblast growth factors and proinflammatory cytokines appear to be able partially to overcome this downregulation and to increase collagen synthesis.
authors.affiliation: Skin Research Group, Division of Clinical Sciences (North), University of Sheffield, UK. caroline.a.harrison@btinternet.com
authors.forename: C A
authors.initials: CA
authors.lastname: Harrison
authors.forename: F
authors.initials: F
authors.lastname: Gossiel
authors.forename: A J
authors.initials: AJ
authors.lastname: Bullock
authors.forename: T
authors.initials: T
authors.lastname: Sun
authors.forename: A
authors.initials: A
authors.lastname: Blumsohn
authors.forename: S
authors.initials: S
authors.lastname: Mac Neil
mesh_terms: D002450:Cell Communication / Q000502:physiology; D002478:Cells, Cultured; D018920:Coculture Techniques; D024042:Collagen Type I / Q000096:biosynthesis*; D017077:Culture Media, Conditioned / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D005326:Fetal Proteins / Q000096:biosynthesis*; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D015603:Keratinocytes / Q000502:physiology*; D008934:Mitogens / Q000494:pharmacology; D010446:Peptide Fragments; D011347:Procollagen; D012867:Skin / Q000378:metabolism*
chemical_list: D024042:Collagen Type I; D017077:Culture Media, Conditioned; D005326:Fetal Proteins; D008934:Mitogens; D010446:Peptide Fragments; D011347:Procollagen; C047202:procollagen Type I N-terminal peptide; D016222:Fibroblast Growth Factor 2; D007334:Insulin-Like Growth Factor I