The evaluation of reactive oxygen species generation and free mitochondrial DNA in platelet concentrates during 5 days of storage

Oxidative stress and mitochondrial damage are causes of platelet storage lesions (PSLs). Mitochondrial damage causes mitochondrial DNA (mtDNA) to be released into the extracellular space. MtDNA in platelet concentrates is considered damage-associated molecular patterns (DAMPs) and is one of the major causes of PSLs. The mechanism of mtDNA release in platelet concentrates has not been thoroughly investigated. This study aimed to determine the effect of reactive oxygen species (ROS) on mtDNA release in platelet concentrates during storage. Ten platelet concentrates from healthy donors were obtained in this investigation. Platelet concentrates were prepared by platelet-rich plasma (PRP) and stored at 22 ± 2 C° with gentle agitation. Platelet concentrates were subjected to flow cytometry and real-time PCR to evaluate total ROS and free mtDNA on days 0, 3, and 5 of platelet concentrate storage. Total ROS detected significantly increased from day 0 to day 5 of platelet concentrate storage (P = 0.0079). The mean of copy numbers of free mtDNA on day 0 increased from 3.43 × 106 ± 1.57 × 106 to 2.85 × 107 ± 1.51 × 107 (molecules/μl) on the fifth day of platelet concentrate storage, and it was statistically significant (P = 0.0039). In addition, LDH enzyme activity significantly increased during platelet concentrate storage (P < 0.0001). Also, releasing mtDNA in platelet concentrates was directly correlated with total ROS generation (P = 0.021, r = 0.61) and LDH activity (P = 0.04, r = 0.44). The evidence from this study confirmed the increasing level mtDNA copy numbers in platelet concentrates during storage, and the amount of free mtDNA is directly correlated with ROS generation and platelet lysis during 5 days of platelet concentrate storage. Finally, these changes may be related to DAMPs in the platelet concentrates.