Prevention of cold-induced apoptosis in platelets from humans and 13-lined ground squirrels

Abstract

Platelets are blood cells involved in blood clotting. Human platelets stored in the cold undergo apoptosis, a process also known as programmed cell death, and are swiftly eliminated from circulation following transfusion. As a result, platelets are typically stored for five days at room temperature due to concerns regarding microbial contamination. The platelets of hibernating mammals, such as 13-lined ground squirrels (Ictidomys tridecemlineatus), remain in circulation after storage at 4°C, deeming this organism a novel animal model for cold storage of platelets. When ground squirrel platelets are cooled, they adopt a rod-like shape that can be stabilized by Taxol, a chemotherapeutic drug. Human and ground squirrel platelets were stored at room temperature and 4°C for five days, both with and without Taxol or EGTA, a calcium chelating agent. Human platelets stored in cold conditions exhibited a rise in expression of apoptotic markers, a change mitigated by EGTA, but not by Taxol. Ground squirrel platelets stored in cold conditions showed reduced apoptosis levels compared to those stored at room temperature, regardless of Taxol and EGTA treatment. To explore mechanisms by which ground squirrels evade platelet apoptosis, the glycoprotein 1bα receptors were tagged with fluorescent-labelled antibodies in samples of both human and squirrel platelets. When analyzed using Fluorescence Resonance Energy Transfer (FRET), previous research showed that human platelets stored in cold showed an increase in FRET consistent with clustering of receptors. We repeated this experiment with human platelets and ground squirrel platelets stored in cold but did not see any evidence of clustering in both human and ground squirrel.