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Background and Objective: In regenerative dentistry, platelet preparations are applied to stimulate bone healing and periodontal regeneration. Here, we pursue a strategy where bone substitutes are used as carriers for platelet-released supernatants. The mitogenic capacity and release kinetics of loaded bone substitutes were assessed., Material and Methods: Platelet-released supernatants of washed platelets (washed PRS) and platelet-released supernatants of unwashed platelets (unwashed PRS) were lyophilized onto the bone substitutes deproteinized bovine bone mineral, hydroxyapatite and β-tricalcium phosphate. Scanning electron microscopy images were taken. Supernatants of bone substitutes were collected at hours 1, 3, 6, 24, and 48 and medium was replaced. We evaluated the protein content with the bicinchoninic acid assay and the effect on proliferation using bioassays with human periodontal fibroblasts. Release of growth factors from the loaded bone substitutes was measured based on the platelet-derived growth factor isoform (PDGF-BB) and thrombin immunoassays. Furthermore, we assessed DNA and RNA content of washed PRS and unwashed PRS., Results: Unwashed PRS showed higher total protein concentrations than washed PRS, while the concentration of PDGF-BB, thrombin, DNA, RNA and their mitogenic effect was not significantly different. The bone substitute materials adsorbed protein over time but no significant changes in overall appearance was found. Supernatants collected from unwashed PRS-loaded bone substitute after 1 h induced a potent mitogenic response in periodontal fibroblasts. This pro-mitogenic capacity of the supernatants decreased over the observation period. Supernatants of washed PRS-loaded bone substitutes did not induce a substantial mitogenic effect. Levels of PDGF-BB, thrombin and protein were higher in supernatants of unwashed PRS-loaded bone substitutes than of washed PRS-loaded bone substitutes., Conclusion: Bone substitutes loaded with unwashed PRS, but not bone substitutes loaded with washed PRS show continuously declining release kinetics. These data suggest that plasma components in platelet preparations can modify the release kinetics profile., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Agis H, Stampfl B, Watzek G, Gruber R. Activated platelets increase proliferation and protein synthesis of human dental pulp–derived cells. International Endodontic Journal, 43, 115–124, 2010. Aim To evaluate the impact of activated platelets on the mitogenic expansion of human dental pulp–derived cells (DPC) in vitro. Methodology The effect of supernatants released from activated platelets (PRS) and the corresponding platelet membranes (MEM) on proliferation and protein synthesis of DPC was evaluated. The contributions of the phosphoinositide 3-kinase (PI3K)/AKT and mitogen-activated protein kinase (MAPK) pathways to the response of DPC were assessed using kinase inhibitors. Also examined was whether the presence of calcium hydroxide or the inflammatory mediators tumour necrosis factor alpha, interleukin-1, interleukin-6 and lipopolysaccharide of Escherichia coli modulated the expansion of DPC. Results Physiologic concentrations of PRS and MEM stimulated proliferation and protein synthesis by 18.4-fold ( P < 0.01) and 2.9-fold ( P < 0.01), respectively. This mitogenic expansion was paralleled by activation of AKT and the MAP kinases extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and p38. Inhibitor studies revealed that the mitogenic response of DPC involved PI3K/AKT, JNK and p38 signalling ( P < 0.05). Calcium hydroxide and inflammatory factors did not significantly modulate the mitogenic response of DPC to PRS and MEM. Conclusion Supernatants released from activated platelets and the corresponding platelet membranes stimulated DPC proliferation and protein synthesis involving PI3K/AKT and MAPK signalling. These findings may serve as a basis for preclinical studies that address the role of activated platelets in dental pulp repair. [ABSTRACT FROM AUTHOR]

Background Different systems for preparation of platelet-rich plasma are commercially available, but data for comparison of these systems have not been published so far. Materials and Methods We investigated the performance of Vivostat PRF Preparation Kit®, PCCS Platelet Concentrate Collection System®, Harvest® SmartPReP 2 APC 60 Process, and Fibrinet® Autologous Fibrin & Platelet System. The preparations provided by these systems are platelet concentrates with high numbers of platelets in a small volume of plasma and PDGF-AB is released continuously during the 5 days after preparation. Results Vivostat PRF Preparation Kit, PCCS Platelet Concentrate Collection System, Harvest SmartPReP 2 APC 60 Process are comparable in platelet yield and total amount of released PDGF-AB after 120 h while with Fibrinet the lowest platelet yield and PDGF-AB content of supernatant was achieved. The ability of growth factor release was equal in all four systems. Conclusion In conclusion, all four systems for preparation of platelet-rich plasma investigated result in considerable growth factor release. In what extent the total content of PDGF-AB as a consequence of platelet yield has an impact on wound healing has to be further investigated [ABSTRACT FROM AUTHOR]