Expired liquid preserved platelet releasates retain proliferative activity

BACKGROUND: Donated platelets for clinical use currently have a shelf life of 5 days as the result of possible bacterial contamination and loss of hemostatic function. Platelet releasates contain multiple growth factors that have been shown to accelerate wound healing. We sought to demonstrate that although expired platelets can no longer sustain hemostasis, they serve a longer term role as a reservoir of growth factors that could be harnessed in wound healing applications. MATERIALS AND METHODS: Liquid preserved human platelets were activated from 1 to 21 days after collection using zeolite and were then analyzed for their ability to stimulate human fibroblast proliferation, which is an in vitro serogate of growth factor activity and wound healing potential. Total protein content, the concentration of platelet-derived growth factor (PDGF) and transforming growth factor-beta were also measured. RESULTS: Activated liquid preserved platelet releasates significantly stimulated fibroblast proliferation. Twenty-one-day-old platelets were as stimulatory as 2-day-old platelets. Total protein concentration, PDGF, and transforming growth factor-beta concentrations remained constant throughout the 21-day course. Western blot analysis using an antibody against human PDGF revealed minimal protein degradation over time. CONCLUSIONS: These data demonstrate that although the role of platelets as hemostatic agents degrades rapidly with time, platelets' ability to serve as a reservoir for growth factors remains intact for at least 3 weeks. These growth factors could be collected, stored, and used as a topical agent to promote healing of chronic and recalcitrant wounds.