title: Platelet activation by collagen provides sustained release of anabolic cytokines.
abstract: BACKGROUND
  Platelet-rich plasma (PRP) has been increasingly used in sports medicine applications. Platelets are thought to release growth factors important in wound healing, including transforming growth factor (TGF-β1), platelet-derived growth factor (PDGF-AB), and vascular endothelial growth factor (VEGF). However, little is known about the effect of platelet activator choice on growth factor release kinetics.
  
  
  OBJECTIVE
  The choice of platelet activator would affect the timing and level of growth factor release from PRP.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Platelet-rich plasma aliquots were activated with either thrombin or collagen. A control group of whole blood aliquots was clotted with thrombin. Supernatant containing the released growth factors was collected daily for 1 week. Levels of TGF-β1, PDGF-AB, and VEGF were measured using enzyme-linked immunosorbent assay (ELISA).
  
  
  RESULTS
  The use of thrombin as an activator resulted in immediate release of TGF-β1 and PDGF-AB, while the collagen-activated PRP clots released similar amounts each day for 5 days. The use of collagen as an activator resulted in an 80% greater cumulative release of TGF-β1 from the PRP aliquots over 7 days (P < .001). Concentrating platelets to 3 times the systemic blood level resulted in a 3-fold higher release of TGF-β1, 2.5-fold greater release of PDGF, and 5-fold greater release of VEGF (all P < .0001) when compared with whole blood control clots, but no significant differences in the timing of release were noted.
  
  
  CONCLUSIONS
  These experiments demonstrated that the choice of platelet activator can significantly influence the release kinetics of cytokines from PRP, with thrombin resulting in an immediate release and collagen having a more sustained release pattern.
  
  
  CONCLUSIONS
  The level and rate of growth factor release depends on the selected platelet activator, a factor that should be considered when selecting a PRP system for a given application.
authors.affiliation: Department of Orthopaedic Surgery, Children’s Hospital of Boston, Massachusetts 02115, USA.
authors.forename: Sophia
authors.initials: S
authors.lastname: Harrison
authors.forename: Patrick
authors.initials: P
authors.lastname: Vavken
authors.forename: Sherwin
authors.initials: S
authors.lastname: Kevy
authors.forename: May
authors.initials: M
authors.lastname: Jacobson
authors.forename: David
authors.initials: D
authors.lastname: Zurakowski
authors.forename: Martha M
authors.initials: MM
authors.lastname: Murray
mesh_terms: D000328:Adult; D003094:Collagen / Q000494:pharmacology*; D016207:Cytokines / Q000096:biosynthesis*; D005260:Female; D006801:Humans; D008297:Male; D015539:Platelet Activation / Q000187:drug effects*; D010982:Platelet-Derived Growth Factor / Q000032:analysis / Q000187:drug effects; D053657:Platelet-Rich Plasma / Q000187:drug effects* / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1 / Q000097:blood / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000097:blood / Q000187:drug effects
chemical_list: D016207:Cytokines; D010982:Platelet-Derived Growth Factor; D053773:Transforming Growth Factor beta1; D042461:Vascular Endothelial Growth Factor A; C095477:platelet-derived growth factor AB; D003094:Collagen; D013917:Thrombin