title: Platelet-rich concentrates differentially release growth factors and induce cell migration in vitro.
abstract: BACKGROUND
  Platelet-rich concentrates are used as a source of growth factors to improve the healing process. The diverse preparation protocols and the gaps in knowledge of their biological properties complicate the interpretation of clinical results.
  
  
  OBJECTIVE
  In this study we aimed to (1) analyze the concentration and kinetics of growth factors released from leukocyte- and platelet-rich fibrin (L-PRF), leukocyte- and platelet-rich plasma (L-PRP), and natural blood clot during in vitro culture; (2) investigate the migration of mesenchymal stem cells (MSCs) and human umbilical vein endothelial cells (HUVECs) as a functional response to the factors released; and (3) uncover correlations between individual growth factors with the initial platelet/leukocyte counts or the induced cell migration.
  
  
  METHODS
  L-PRF, L-PRP, and natural blood clot prepared from 11 donors were cultured in vitro for 28 days and media supernatants collected after 8 hours and 1, 3, 7, 14, and 28 days. Released transforming growth factor β1 (TGF-β1), vascular endothelial growth factor (VEGF), insulin growth factor (IGF-1), platelet-derived growth factor AB (PDGF-AB), and interleukin-1β (IL-1β) were measured in the supernatants with enzyme-linked immunosorbent assay. Migration of MSC and HUVEC induced by the supernatants was evaluated in Boyden chambers.
  
  
  RESULTS
  More TGF-ß1 was released (mean ± SD in pg/mL of blood) from L-PRF (37,796 ± 5492) compared with L-PRP (23,738 ± 6848; p < 0.001) and blood clot (3739 ± 4690; p < 0.001), whereas more VEGF and IL-1ß were released from blood clot (1933 ± 704 and 2053 ± 908, respectively) compared with both L-PRP (642 ± 208; p < 0.001 and 273 ± 386; p < 0.001, respectively) and L-PRF (852 ± 376; p < 0.001 and 65 ± 56, p < 0.001, respectively). No differences were observed in IGF-1 and PDGF-AB released from any of the concentrates. TGF-β1 release peaked at Day 7 in L-PRF and at 8 hours and Day 7 in L-PRP and 8 hours and Day 14 in blood clot. In all concentrates, main release of VEGF occurred between 3 and 7 days and of IL-1β between Days 1 and 7. IGF-1 and PDGF-AB were released until Day 1 in L-PRP and blood clot, in contrast to sustained release over the first 3 days in L-PRF. The strongest migration of MSC occurred in response to L-PRF, and more HUVEC migration was seen in L-PRF and blood clot compared with L-PRP. TGF-β1 correlated with initial platelet counts in L-PRF (Pearson r = 0.66, p = 0.0273) and initial leukocyte counts in L-PRP (Pearson r = 0.83, p = 0.0016). A positive correlation of IL-1β on migration of MSC and HUVEC was revealed (Pearson r = 0.16, p = 0.0208; Pearson r = 0.31, p < 0.001).
  
  
  CONCLUSIONS
  In comparison to L-PRP, L-PRF had higher amounts of released TGF-β1, a long-term release of growth factors, and stronger induction of cell migration. Future preclinical studies should confirm these data in a defined injury model.
  
  
  CONCLUSIONS
  By characterizing the biologic properties of different platelet concentrates in vitro, we may gain a better understanding of their clinical effects and develop guidelines for specific future applications.
authors.affiliation: Department of Clinical Research, University of Bern, Bern, Switzerland.
authors.forename: Michael O
authors.initials: MO
authors.lastname: Schär
authors.forename: Jose
authors.initials: J
authors.lastname: Diaz-Romero
authors.forename: Sandro
authors.initials: S
authors.lastname: Kohl
authors.forename: Matthias A
authors.initials: MA
authors.lastname: Zumstein
authors.forename: Dobrila
authors.initials: D
authors.lastname: Nesic
mesh_terms: D001792:Blood Platelets / Q000378:metabolism*; D002465:Cell Movement; D002478:Cells, Cultured; D005337:Fibrin / Q000378:metabolism; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000097:blood*; D053583:Interleukin-1beta / Q000097:blood; D007700:Kinetics; D007962:Leukocytes / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D053657:Platelet-Rich Plasma / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000097:blood; D042461:Vascular Endothelial Growth Factor A / Q000097:blood
chemical_list: C583557:IGF1 protein, human; C508585:IL1B protein, human; D036341:Intercellular Signaling Peptides and Proteins; D053583:Interleukin-1beta; D010982:Platelet-Derived Growth Factor; C508960:TGFB1 protein, human; D053773:Transforming Growth Factor beta1; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C095477:platelet-derived growth factor AB; D007334:Insulin-Like Growth Factor I; D005337:Fibrin