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The impact of plasma on cold storage of APC
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CD
Figure 6. Flow cytometric analysis of apheresis platelet concentrates produced under Good Manufacturing Practice (GMP) conditions. Apheresis platelet concen- trates (APCs) were produced under GMP conditions. Platelet (PLT) activation was measured at the indicated storage time for room temperature (RT) and 4°C stored PLTs. The expression of (A) CD62P, (B) CD63 and (C) PAC1 was analyzed after activation with TRAP. (D) The ability of apheresis platelet concentrates (APCs) to react on a hypotonic environment was determined as hypotonic shock reaction by light transmission aggregometry. Data are shown as mean±Standard Error of Mean. ***P<0.001; ****P<0.0001. ns: not significant (n=4).
the von Willebrand factor binding to GPIb-α, inducing increased intracellular calcium concentration and phos- phatidylserine exposure leading to a rapid clearance of PLTs. The authors demonstrated that the inhibition of this binding and the consequent downstream cascade, using a specific peptide that recognizes GPIb-α, significantly increased recovery and life-span of cold-stored PLTs.28 Another study showed that a specific caspase-3 inhibitor significantly improves PLT functionality and viability dur- ing seven days of storage.29 This, together with our results, suggests that inhibition of apoptosis seems to be a promis- ing approach to reduce cold-stored lesions.
Another important finding of our study is that in vivo survival of cold-stored PLTs was independent of varying plasma contents. However, remarkably poor in vitro results of PLT function were observed in APCs stored at too low a plasma concentration (PAS-20-APC). This further sup- ports in vivo studies of Slichter et al. who used radiolabeled autologous PLTs and showed that RT storage in 80% Plasmalyte (a PAS which is FDA approved) is associated with lower recovery and survival compared to PLTs stored in 100% plasma or 35% residual plasma.30
Finally, we investigated whether our research findings could be transferred to routine production and explored the possibility of extending PC shelf-life. To exclude the influence of different donors, we designed a follow-up study where each donor donated double APCs in PAS con-
taining 35% plasma. Each APC was stored either at RT or at 4°C for up to ten days. We found that PLTs from APCs collected and stored under routine blood bank conditions at 4°C maintained functionality better in terms of activa- tion (granule release in response to TRAP) and aggregation compared to those stored at RT. These results correspond to those from the split design study. Taken together, a residual plasma content of approximately 35% is feasible for cold storage of PLTs in APCs for clinical use. Our results indicate the potential of prolonging shelf-life of GMP-produced APCs stored at 4°C for clinical use.
In summary, our study provides additional information on the in vitro hemostatic function and in vivo survival of cold-stored PLTs, and suggests that PLTs stored in PAS at 4°C could become an alternative to the current standard of care.
Funding
The study was supported by a grant from the German Red Cross, Blutspendedienst Baden-Württemberg-Hessen. The authors would like to thank Ulrike Strobel, Lars Jansen, Robert Koch, Flavianna Rigoni, Kati Sevke-Masur and Inga Miksa for their excellent technical support.
Acknowledgments
We thank Stephen Bosher for his contribution to the manuscript as a native English speaker.
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