Platelet lysate converts M (IFNγ+LPS) macrophages in CD206+ TGF-β+ arginase+ M2-like macrophages that affect fibroblast activity and T lymphocyte migration.

Abstract

Macrophages, thanks to their extreme plasticity, exert critical roles in wound healing by orchestrating tissue defenses in the early inflammatory phase, and by promoting tissue regeneration and angiogenesis at a later time point. In parallel, platelets release a large number of preformed molecules that could affect immunocyte functions. Platelet-rich plasma and platelet lysate (PL) have been widely used as a therapeutic preside for ulcers, although little is known about the effects of platelet-derived biomolecules on macrophage functions during wound healing. In this study, we analyze the effects of PL on macrophages phenotype and functions. Monocyte-derived macrophages were cultured in the presence of interferon-γ and lipopolysaccharides to induce the M1 polarization and were further exposed to 10% PL. PL treatment reduced CD80, CD86, and PDL-1 and enhanced CD206 and CD200R expression on macrophages analyzed by cytofluorimetry. Additionally, macrophage cultures show reduced TNF-α and CXCL10, while increased arginase protein, PPAR, TGF-β, and VEGF. TGF-β secretion was paralleled by the decrease of NFkB and increase of STAT3, STAT6, and SMAD2 and SMAD4. Supernatants of PL-treated macrophages induced a significant increase of type-I collagen and to a lesser extent of type-III collagen production by fibroblasts. Finally, the supernatant of PL-treated macrophages showed significantly reduced capacity to induce the in vitro migration of T lymphocytes. Our results demonstrate that PL dampens the macrophage secretion of pro-inflammatory cytokines and induces the release of arginase, TGF-β, and VEGF that may affect angiogenesis and tissue regeneration, thus facilitating the wound healing process.