Platelet ultrastructural changes stored at room temperature versus cold storage observed by electron microscopy and...

Our study seeks to provide a theoretical foundation for the clinical use of cold-stored platelets (CSPs) by interpreting ultrastructural images and quantitatively analyzing structural changes. CSPs, room temperature-stored platelets (RTPs), and delayed CSPs (delayed-CSPs) were continuously observed using scanning electron microscopy and transmission electron microscopy at eight time points. Super-resolution fluorescence microscopy was employed to observe changes in platelet microtubules and mitochondrial structure and function, whereas platelet counts, metabolism, and relevant functional indicators were measured concurrently. Quantitative statistical analysis of platelet size, morphology, canalicular systems, and five organelles was performed under electron microscopy. In CSPs stored for 1 day, the platelet shape changed from circular or elliptical to spherical, with size decreasing from 2.8 × 2.2 µm to 2.0 × 2.0 µm. CSPs exhibited wrinkling and reorganization of platelet microtubule proteins, with organelles aggregating toward the central region. CSPs stored for 14 days and delayed-CSPs for stored for 10 days exhibited numerous structurally intact and active cells. The percentage of structure-intact active cells was 92% in both groups, respectively. RTPs stored for 5 and 7 days showed minimal changes in size, a normal microtubule skeleton, and were primarily in a resting state. However, RTPs stored for 10 and 14 days displayed swelling, irregular disintegration of the microtubule skeleton, and the presence of membranous structures and vacuolated cells. The percentage of structure-intact active cells was only 45% and 7%, respectively. Our findings confirmed that the maximum storage time of platelets was 5-7 days for RTPs, within 10 days for delayed-CSPs, and 14 days for CSPs.