Platelet activation by collagen provides sustained release of anabolic cytokines

Am J Sports Med. 2011 Apr;39(4):729-34. doi: 10.1177/0363546511401576. Epub 2011 Mar 11.


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.

Hypothesis: The choice of platelet activator would affect the timing and level of growth factor release from PRP.

Study design: 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.

Conclusion: 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.

Clinical relevance: 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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Collagen / pharmacology*
  • Cytokines / biosynthesis*
  • Female
  • Humans
  • Male
  • Platelet Activation / drug effects*
  • Platelet-Derived Growth Factor / analysis
  • Platelet-Derived Growth Factor / drug effects
  • Platelet-Rich Plasma / drug effects*
  • Platelet-Rich Plasma / metabolism
  • Thrombin / pharmacology*
  • Transforming Growth Factor beta1 / blood
  • Transforming Growth Factor beta1 / drug effects
  • Vascular Endothelial Growth Factor A / blood
  • Vascular Endothelial Growth Factor A / drug effects


  • Cytokines
  • Platelet-Derived Growth Factor
  • Transforming Growth Factor beta1
  • Vascular Endothelial Growth Factor A
  • platelet-derived growth factor AB
  • Collagen
  • Thrombin