In vitro effects of cold storage on human and 13-lined ground squirrel platelet apoptosis

Abstract

Platelet transfusions are an essential therapy for conditions resulting in thrombocytopenia. Platelet storage time at room temperature is limited to five days due to microbial contamination and platelet storage lesions. The potential for cold storage remains to be seen as human platelets stored at 4o C are rapidly cleared from circulation post-transfusion. Unlike human platelets, the platelets of the 13-lined ground squirrel are not rapidly cleared from circulation if they are chilled prior to transfusion. To investigate if the rapid clearance of cold-stored platelets from circulation is due to apoptosis, programmed cell death, human and ground squirrel platelets were isolated, stored at room temperature or 4o C, labelled with fluorescent markers of apoptosis, and analyzed by flow cytometry. Cold storage (4o C) caused human platelets to display significant (p<0.05) increases in phosphatidylserine surface expression and caspase activation after only 3 days and progressively increased throughout storage, indicating that apoptosis has occurred. In contrast, no significant changes were observed in ground squirrel platelets stored at 4o C relative to fresh sample. These results suggest that ground squirrels have developed physiological mechanisms that prevent their platelets from undergoing apoptosis when stored in the cold, potentially contributing to their platelets remaining in circulation during and following hibernation.