title: Platelets stimulate fibroblast-mediated contraction of collagen gels.
abstract: BACKGROUND
  Platelets are thought to play a role in a variety of inflammatory conditions in the lung, some of which may lead to fibrosis. In the current study we tested the hypothesis that whole platelets and platelet lysate can mediate remodelling of extracellular matrix in vitro by affecting fibroblast-mediated contraction of a collagen gel. We also sought to determine to what extent platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) contribute to this effect.
  
  
  METHODS
  Washed platelets, isolated from healthy blood donors, and platelet lysate (freezing and thawing), were cast together with human lung fibroblasts in three-dimensional collagen gels. The gels were then released and cultured for four days. PDGF and TGF-beta1 concentrations were measured in culture supernatants by ELISA.
  
  
  RESULTS
  Both platelets and platelet lysate augmented fibroblast-mediated gel contraction in a time and concentration dependent manner (19.9% +/- 0.1 (mean +/- SEM) of initial area vs. 48.0% +/- 0.4 at 48 hours; P < 0.001 and 41.5% +/- 0.6 vs. 60.6% +/- 0.3 at 48 hours; P < 0.001, respectively). Fixed platelets had no effect in the system. Both TGF-beta1 and PDGF-AA/AB were released in co-culture. PDGF-AA/AB had a maximum release at 24 hours whereas TGF-beta1 release increased with longer culture periods. Neutralising antibodies to these mediators partially inhibited platelet-induced gel contraction.
  
  
  CONCLUSIONS
  We conclude that platelets may promote remodelling of extracellular matrix in vitro and that PDGF and TGF-beta partially mediate this effect, also indicating a role for other mediators. The findings may be an important mechanism in regulating repair processes after injury.
authors: Department of Medicine, Karolinska Hospital, Stockholm, Sweden. ulrika.zagai@ks.se
authors: Ulrika
authors: U
authors: Zagai
authors: Karin
authors: K
authors: Fredriksson
authors: Stephen I
authors: SI
authors: Rennard
authors: Joachim
authors: J
authors: Lundahl
authors: C Magnus
authors: CM
authors: Sköld
mesh_terms: D000906:Antibodies / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D018920:Coculture Techniques; D003094:Collagen / Q000187:drug effects / Q000502:physiology*; D004247:DNA / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology; D005347:Fibroblasts / Q000378:metabolism / Q000502:physiology*; D005404:Fixatives / Q000494:pharmacology; D005557:Formaldehyde / Q000494:pharmacology; D005615:Freezing; D005782:Gels; D006801:Humans; D008168:Lung / Q000196:embryology*; D009994:Osmolar Concentration; D010982:Platelet-Derived Growth Factor / Q000276:immunology / Q000378:metabolism; D011108:Polymers / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000276:immunology / Q000378:metabolism
chemical_list: D000906:Antibodies; D005404:Fixatives; D005782:Gels; D010982:Platelet-Derived Growth Factor; D011108:Polymers; D016212:Transforming Growth Factor beta; D005557:Formaldehyde; D003094:Collagen; D004247:DNA; C003043:paraform