Platelet apoptosis and activation in platelet concentrates stored for up to 12 days in plasma or additive solution

Several studies suggest that apoptosis of platelets occurs during storage of platelet concentrates (PC). We sought to determine whether storage of PC in additive solution alters levels of apoptosis during storage beyond the current shelf life (5-7 days).

Pooled buffy coat PC (n = 7) were prepared in either 100% plasma or 70% Composol and stored at 22 °C for 12 days. A third arm of the study stored PC in 100% plasma at 37 °C, which is thought to induce apoptosis. PC were tested for mitochrondrial membrane potential, annexin V binding, microparticles, caspase-3/7 activity and decoy cell death receptor 2, as well as standard platelet quality tests.

Composol units remained ≥pH 6·88, with 36% lower lactate and higher pH vs plasma by day 12 (P < 0·001). Platelet function was better maintained, and activation and apoptotic markers tended to be lower in Composol units towards the end of storage. However, levels of all apoptosis markers assessed were not significantly different in units stored in Composol. Storage at 37 °C saw stronger correlation of apoptotic markers with standard quality tests compared to 22 °C, but loss of correlation of caspase-3/7 activity with other apoptosis markers.

We conclude that storage of platelets in 70% Composol vs 100% plasma does not increase the rate of platelet apoptosis. Our data agree with other studies suggesting that platelet apoptosis is sequential to high levels of activation, but share a significant degree of overlap.