Anti-inflammatory effects of platelet biomaterials in a macrophage cellular model.

Recent clinical data suggested that platelet materials used in regenerative medicine exert anti-inflammatory effects. One must understand whether functionality varies among platelet preparations and also the role of the various protein compartments. Platelet-poor-plasma (PPP), platelet lysate with cell debris (PL) or cell-free (CFPL), platelet gel releasate (PGR) and solvent/detergent-treated PL (SDPL) were prepared from four apheresis platelet donations. Protein profile was examined by SDS-PAGE, and growth factors and cytokines by ELISA, multiplexed Luminex assay and cytokine array. Anti-inflammatory activity was evaluated in RAW 264.7 mouse macrophages treated for 24 h with the blood fractions followed by 24 h of stimulation with 500 ng/ml lipopolysaccharides (LPS). Inflammatory marker nitric oxide (NO) was determined by colorimetry, tumour necrosis factor (TNF)-α by ELISA and inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 by Western blotting. Proteins, growth factors and cytokines composition differed among preparations. Blood fractions alone did not stimulate inflammatory markers expression. Following LPS stimulus, NO and iNOS expressions were significantly inhibited (P < 0.001) by all blood fractions, but inhibition was more pronounced with SDPL. In addition, only SDPL inhibited TNF-α (P < 0.001) and COX-2 expressions. All the plasma and platelet fractions evaluated in this study exert an anti-inflammatory effect on macrophages, suggesting that both the plasma and platelet proteomes contribute to anti-inflammation. However, the extent and nature of the anti-inflammatory action vary among products. Further studies are needed to better understand the functionality of platelet biomaterials and optimize their clinical use.