The Activity of Monocyte-Derived Macrophages after Stimulation with Platelet-Rich and Platelet-Poor Concentrates. Study on an Ovine Model of Insertion of a Tibial Implant Coated with Silicon-Doped Diamond-Like Carbon

Introduction: Macrophages are crucial immune cells that play a role in tissue repair and can exhibit pro- or anti-inflammatory behaviour based on environmental stimulation. Their functional phenotype can be affected by platelet-derived products as determined by those products' composition. When the inflammatory response caused by implantation is excessive, it can lead to rejection of the implant. Therefore, a thorough evaluation of implant haemocompatibility is necessary to minimise undesirable consequences. Material and Methods: In an in vitro study, monocyte-derived macrophages (MDMs) were obtained from the whole blood of sheep after a silicon-doped diamond-like carbon-coated implant insertion. These MDMs were then exposed to autologous platelet-derived products for functional marker analysis. Results: Platelet-poor plasma (PPP) and pure platelet-rich plasma (P-PRP) stimulation increased arginase-1 activity, while leukocyte-rich PRP stimulation produced a mixed response involving higher O-2(-) (6.49 +/- 2.43 nM vs non-stimulated 3.51 +/- 1.23 nM, P-value < 0.05) and NO (3.28 +/- 1.38 mu M vs non-stimulated 2.55 +/- 0.32 mu M, P-value < 0.05) generation. Conclusion: Using PPP and P-PRP stimulation in post-implantation procedures may contribute to the polarisation of macrophages towards the M2-like pro-resolving phenotype, thereby accelerating wound healing. This would also prevent implant degradation due to an excessive inflammatory process.