Divalent magnesium restores cytoskeletal storage lesions in cold-stored platelet concentrates

Cold storage of platelet concentrates (PC) has become attractive due to the reduced risk of bacterial proliferation, but in vivo circulation time of cold-stored platelets is reduced. Ca²⁺ release from storage organelles and higher activity of Ca²⁺ pumps at temperatures < 15 °C triggers cytoskeleton changes. This is suppressed by Mg²⁺ addition, avoiding a shift in Ca²⁺ hemostasis and cytoskeletal alterations. We report on the impact of 2-10 mM Mg²⁺ on cytoskeleton alterations of platelets from PC stored at room temperature (RT) or 4 °C in additive solution (PAS), 30% plasma. Deformation of platelets was assessed by real-time deformability cytometry (RT-DC), a method for biomechanical cell characterization. Deformation was strongly affected by storage at 4 °C and preserved by Mg²⁺ addition ≥ 4 mM Mg²⁺ (mean ± SD of median deformation 4 °C vs. 4 °C + 10 mM Mg²⁺ 0.073 ± 0.021 vs. 0.118 ± 0.023, p < 0.01; n = 6, day 7). These results were confirmed by immunofluorescence microscopy, showing that Mg²⁺  ≥ 4 mM prevents 4 °C storage induced cytoskeletal structure lesion. Standard in vitro platelet function tests showed minor differences between RT and cold-stored platelets. Hypotonic shock response was not significantly different between RT stored (56.38 ± 29.36%) and cold-stored platelets with (55.22 ± 11.16%) or without magnesium (45.65 ± 11.59%; p = 0.042, all n = 6, day 1). CD62P expression and platelet aggregation response were similar between RT and 4 °C stored platelets, with minor changes in the presence of higher Mg²⁺ concentrations. In conclusion, increasing Mg²⁺ up to 10 mM in PAS counteracts 4 °C storage lesions in platelets, maintains platelet cytoskeletal integrity and biomechanical properties comparable to RT stored platelets.