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

Background and Objectives: 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. Materials and Methods: 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. Results: 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. Conclusions: 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.