Leukocyte Platelet-Rich Fibrin (L-PRF), a new biomembrane useful in tissue repair: basic science and literature review

PRF is a second-generation platelet concentrate and can be distinguished in P-PRF (Pure Platelet-rich fibrin) and L-PRF (Leukocyte and Platelet-rich fibrin). In vivo, during the platelet clot formation, platelets are bound to beta-integrin fibrin and the clot retracts itself. The PRF clot forms a solid fibrin matrix, displaying a complex tridimensional architecture. Measuring the levels of PDGF-BB, TGF-1 beta and IGF-1, in the PRF matrix, it was revealed that slow fibrin polymerization during PRF elaboration leads to the intrinsic platelet formation of cytokines and glycan chains inside the fibrin mesh. The PRF proximal part (the part closer to the red clot) contains platelets and leukocytes, found to be massively enclosed inside the fibrin net. Platelet localization inside PRF was examined through immunostaining and scanning electron microscope (SEM). Compared to the abrupt basal compression of PRF membrane (G-PRF), preservation of plasma level, of 3D fibrin, and of platelets was found to be more intact in PRF membrane preparations obtained through metallic compression system (PRF-C) (L-PRF Wound Box). The pure platelet-rich fibrin (P-PRF) and the leukocyte and platelet-rich fibrin (PRF-L) are biomaterials with solid fibrin or biomaterials containing leukocytes. No platelet concentration related problems were found in PRF, as all platelets in the drawn blood sample are activated and integrated inside the fibrin matrix of the clot. Approximately 97% of platelets and more than 50% of leukocytes are concentrated inside the PRF clot, which displays a specific tridimensional distribution. Almost all platelets (>97%) are absent inside test-tubes of groups tested after PRF membrane extraction. Factors freed by platelets contained in L-PRF induce and control the proliferation and migration of other cell types, involved in tissue repair, like smooth cell muscles (SMCs) and mesenchymal stem cells (MSCs).