title: The effect of thrombin activation of platelet-rich plasma on demineralized bone matrix osteoinductivity.
abstract: BACKGROUND
  Demineralized bone matrix is an osteoinductive and osteoconductive material that is often used in orthopaedic surgery to induce bone formation. Autologous platelet-rich plasma, which contains proliferative and chemoattractant growth factors, has been used as a demineralized bone matrix adjuvant with mixed results. One variable during clinical use appears to be whether the platelet-rich plasma is activated with thrombin or is implanted in a liquid form with intact platelets. The objective of the present study was to determine if platelet-rich plasma can increase the osteoinductivity of demineralized bone matrix when used without thrombin activation.
  
  
  METHODS
  The bioactivity of the demineralized bone matrix was evaluated in vitro by determining alkaline phosphatase production by C2C12 myoblast cells. The effect of thrombin activation on platelet-rich plasma was studied in vitro by evaluating osteosarcoma and bone marrow stromal cells for cell number and transforming growth factor-beta1 activation. Demineralized bone matrices supplemented with platelet-rich plasma, with or without thrombin activation, were implanted intramuscularly in athymic rats and were examined at fourteen, twenty-eight, and fifty-six days. Histological samples were analyzed for osteogenesis and chondrogenesis. Osteogenesis was further characterized on the basis of alkaline phosphatase activity.
  
  
  RESULTS
  In vitro, thrombin triggered an immediate release of growth factors from the platelet-rich plasma, and the platelet-rich plasma increased the number of both osteosarcoma and stromal cells in a dose-dependent manner. Thrombin activation of the platelet-rich plasma eliminated such stimulatory effects. In vivo, the platelet-rich plasma stimulated chondrogenesis on Day 14 and osteogenesis on Days 28 and 56, whereas thrombin-activated platelet-rich plasma acted as an inhibitor of such events. In addition, inflammatory cells were detected in demineralized bone matrix samples that were mixed with thrombin-activated platelet-rich plasma. These cells were not present in matrix mixed with platelet-rich plasma alone.
  
  
  CONCLUSIONS
  Platelet-rich plasma significantly increased in vivo demineralized bone matrix osteoinductivity only when used without thrombin activation.
authors.affiliation: Department of Surgery, University of Southern California, 1840 North Soto Street EDM-191, Los Angeles, CA 90032, USA. bohan@usc.edu
authors.forename: Bo
authors.initials: B
authors.lastname: Han
authors.forename: Jennifer
authors.initials: J
authors.lastname: Woodell-May
authors.forename: Michael
authors.initials: M
authors.lastname: Ponticiello
authors.forename: Zhi
authors.initials: Z
authors.lastname: Yang
authors.forename: Marcel
authors.initials: M
authors.lastname: Nimni
mesh_terms: D000328:Adult; D000818:Animals; D015519:Bone Density / Q000502:physiology*; D001857:Bone Matrix / Q000502:physiology / Q000637:transplantation*; D049109:Cell Proliferation; D002478:Cells, Cultured; D020219:Chondrogenesis / Q000187:drug effects* / Q000502:physiology; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D020007:Implants, Experimental; D008297:Male; D051379:Mice; D008819:Mice, Nude; D010012:Osteogenesis / Q000502:physiology*; D010784:Photomicrography; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D053657:Platelet-Rich Plasma / Q000502:physiology*; D012680:Sensitivity and Specificity; D013917:Thrombin / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000097:blood / Q000378:metabolism
chemical_list: D010982:Platelet-Derived Growth Factor; D042461:Vascular Endothelial Growth Factor A; D013917:Thrombin