Platelet-rich fibrin is a bioscaffold and reservoir of growth factors for tissue 6

The platelet-rich fibrin (PRF) is known as a rich source of autologous cytokines and growth factors and uni-versally used for tissue regeneration in current clinical medicine. However, the microstructure of PRF has not been fully investigated nor have been studied the key molecules that differ PRF from platelet-rich plasma. We fabricated PRF under Choukroun’s protocol and produced its extract (PRFe) by freezing at 808C. The con-ventional histological, immunohistological staining, and scanning electron microscopy images showed the mi-crostructure of PRF, appearing as two zones, the zone of platelets and the zone of fibrin, which resembled a mesh containing blood cells. The PRFe increased proliferation, migration, and promoted differentiation of the human alveolar bone marrow stem cells (hABMSCs) at 0.5 % concentration in vitro. From the results of proteome array, matrix metalloproteinase 9 (MMP9) and Serpin E1 were detected especially in PRFe but not in concen-trated platelet-rich plasma. Simultaneous elevation of MMP9, CD44, and transforming growth factor b-1 re-ceptor was shown at 0.5 % PRFe treatment to the hABMSC in immunoblot. Mineralization assay showed that MMP9 directly regulated mineralization differentiation of hABMSC. Transplantation of the fresh PRF into the mouse calvarias enhanced regeneration of the critical-sized defect. Our results strongly support the new char