title: Transforming growth factor-beta, Smad, and collagen expression patterns in fetal and adult keratinocytes.
abstract: BACKGROUND
  The transforming growth factor (TGF)-beta family regulates cellular proliferation, differentiation, and migration. To better define the influence of keratinocyte-derived TGF-beta during development and repair, the authors examined the TGF-beta isoform, receptor, signal messenger Smad, and collagen type I expression in fetal and postnatal keratinocytes.
  
  
  METHODS
  Sprague-Dawley rat keratinocytes were isolated in primary culture from fetal E17 (n = 6), newborn (n = 4), and 6-week-old adults (n = 4). Under serum-free conditions, quantitative polymerase chain reaction was performed for TGF-beta1, TGF-beta2, and TGF-beta3 ligands; TGF-beta receptor 1 (RI) and TGF-beta receptor 2 (RII); Smad4 and Smad7; and collagen type I expression.
  
  
  RESULTS
  Total TGF-beta isoform expression increased 1.7-fold from E17 to newborn (p < 0.05) and adult (p < 0.01) ages. TGF-beta1 expression was 25-fold greater than TGF-beta2 and 10-fold greater than TGF-beta3 in fetal keratinocytes (p < 0.01 for each). The expression of TGF-beta1 was fivefold greater compared with TGF-beta2 and TGF-beta3 in newborn and adult keratinocytes (p < 0.01). TGF-beta-RI expression increased more than twofold (p < 0.01), whereas TGF-beta-RII expression increased by 25 percent (p < 0.01) from E17 to adult age. Smad4 increased more than twofold (p < 0.01), whereas Smad7 did not change appreciably. Collagen type I expression increased over 100-fold from E17 to adult (p < 0.005).
  
  
  CONCLUSIONS
  The TGF-beta system and collagen type I have increased expression with increasing gestational age in keratinocytes. This suggests an increased profibrotic TGF-beta response and collagen type I production in keratinocytes during skin differentiation at ages associated with scarring.
authors.affiliation: Department of Surgery, Division of Plastic Surgery, Children's Surgical Research Program, Tissue Regeneration Laboratory, Stanford University, Stanford, CA 94305-5148, USA.
authors.forename: Amy S
authors.initials: AS
authors.lastname: Colwell
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Faudoa
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Krummel
authors.forename: Michael T
authors.initials: MT
authors.lastname: Longaker
authors.forename: H Peter
authors.initials: HP
authors.lastname: Lorenz
mesh_terms: D000375:Aging / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism; D002478:Cells, Cultured; D024042:Collagen Type I / Q000378:metabolism*; D005333:Fetus / Q000378:metabolism; D005865:Gestational Age; D015603:Keratinocytes / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D051381:Rats; D017207:Rats, Sprague-Dawley; D051785:Smad Proteins / Q000378:metabolism*; D051901:Smad4 Protein / Q000378:metabolism; D051906:Smad7 Protein / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D024042:Collagen Type I; D051785:Smad Proteins; D051901:Smad4 Protein; D051906:Smad7 Protein; D016212:Transforming Growth Factor beta