Preparation and Viral Inactivation of Platelet Lysate

GMP-compliant PL (Mesengen) was prepared and virally inactivated, as previously described [8 (link), 9 (link)]. Briefly, after obtaining informed consent, buffy coats from healthy volunteers were centrifuged and treated with InterSol solution (318 mg Na-citrate 2H₂O, 305 mg Na 2-phosphate anhydro, 105 mg Na dihydrogen phosphate 2H₂O, 442 mg Na-acetate 3H₂O, 452 mg NaCl, 100 mL H₂O, Fenwal Inc., Lake Zurich, Illinois) and subsequently with 20–30% human plasma. Potential pathogens were inactivated by using the Intercept Blood System for Platelets (Cerus Corporation, Concord, California, USA). PL was stored at −80°C for 24 hours before thawing at 37°C for 60 minutes. This procedure was repeated three times to enrich the pool of growth factors. Concentration and sterility of the preparation were determined by the haematology analyzer ABX Pentra DX 120 (Horiba ABX, Montpellier, France) and BACTEC 9240 (Becton and Dickinson), respectively. 5 U/mL heparin was added to cell culture media in order to avoid fibrin gel formation.