Freezing procedure without thrombin activation to retain and store growth factors from platelet concentrates

Background/purposeThe aim of this study was to examine a new procedure of simple freezing without the need of thrombin activation to retain and store growth factors (GFs) from platelet concentrates for up to 6 months.Materials and methodsAfter being re-suspended with Tyrode’s solution, platelet suspensions were divided into four groups. In the negative control group, platelet supernatants were collected after centrifugation and then frozen at −70°C until being tested. In the frozen group, platelet suspensions were directly frozen and stored at −70°C; centrifugation was postponed until just before testing. In the thrombin and post-thrombin groups, the procedures were the same as those of the previous two groups, respectively, except that thrombin was added before centrifugation. Concentrations of platelet-derived GF-AB and tumor GF-β1 were assayed by an ELISA at 0 (the day on which the experiment began), 1, 2, and 4 months in first three groups (Experiment 1), and in all four groups at 6 months (Experiment 2).ResultsSimilar platelet-derived GF-AB and transforming GF-β1 concentrations were recorded in the frozen and thrombin groups with up to 4 months of storage. After 6 months of storage, similar concentrations were recorded among the frozen, thrombin, and post-thrombin groups.ConclusionsBecause of similar concentrations of GFs in all groups, except for the negative control group, after being stored for up to 6 months, we suggest that the concentration of GFs of platelet concentrates can be maintained for at least 6 months, and that GFs in platelet concentrates can be obtained by means of direct freezing, without the necessity of thrombin activation.