Effect of leukocytes included in platelet concentrates on cell behaviour

This literature review's aim is to evaluate the function of white blood cells (WBCs) and to conclude whether leukocyte's inclusion in platelet concentrates promotes or inhibits tissue regeneration. An electronic literature search was performed on MEDLINE through its online site (PubMed) and on the EMBASE database for articles published between 1986 and 2019. Consecutive screenings at the title/abstract and full-text levels were performed. All in vitro studies that reported the comparison of leukocyte-rich and leukocyte-poor platelet concentrates were included. The search included 14 articles that matched the inclusion criteria. A systematic review shows that leukocytes are responsible for less promoted migration and osteogenic differentiation of human bone marrow stem cells (HBMSCs), lesser cartilage cell, gingival fibroblast and osteoblast proliferation. Decreased tendon cell metabolism and a cytotoxic effect of leukocytes on synoviocytes have also been identified. Additionally, leukocytes were accountable for a cytokine (IL-1β, IL-8, TNF-α, MMP-1 and MMP-9) increase and NF‑κB signaling pathway initiation. WBCs were also linked to growth factors (VEGF, PDGF-AA/BB). Leukocyte and platelet functions are alike when considering growth factor release. Nevertheless, in the presence of WBCs, platelet concentrates promote cell migration, proliferation, and differentiation less effectively and are responsible for a potentially prolonged inflammation phase due to cytokine release.