An Experimental Study On The 4℃ Platelet Additive Solution And An Elementary Study On The Mechanisms Of Platelet Storage Lesion By Chilling

Platelets are routinely stored at room temperature (RT, 20-24°C with agitation) which show better function, recov ery and survival. Unfortunately, there is an exponential increase in bacterial contamination in the platelets, resulting in the limitation of 5 days storage and increased incidence of febrile and other transfusion reactions. Platelet cryopreservation excludes the potential for bacterial growth, and leads to longer storage time, but it is hard to use it as a standard process for long-term preservation of platelets due to its special requests in operation, preservation and transportation. In addition, cryoprotective agent DMSO is toxic to the recipients, and it can also lead to platelet activation in the process of freezing and washing. Consequently, platelet recovery and survival are fundamentally decreased after the cryopreservation. So, refrigerated storage of platelet products would be meaningful as: 1) it can decrease the potential for bacterial contamination; 2) products of platelet and red blood cells will use the current equipments and resources in common as they have the same bankig procedures. 3) platelet additive solutions make it possible to introduce photochemical treatment for the virus inactivation of platelet concentrates, and reduce the amount of plasma transfused with platelets, which can be used for plasma fractionation.There are no reports of research on 4°C storage of human platelet in our country, especially research on platelet additive solutions at 4°C. In our study, in vitro assays to evaluate the quality of platelets are founded. To confirm the special platelet storage lesions at cold temperature, platelet concentrates stored at RT and 4°C in plasma were compared with those assays in vitro. The results showed that the qualities of 4°C platelets were significantly different with those of platelets stored at RT, demonstrating that plasma was not the proper solution for platelet storage, instead of plasma, the platelet additive solution may improve the in vitro qualities of platelets.To see whether it is feasible to preserve platelets in the 22°C platelet additive solution (PAS-III) at 4°C, PAS-III was used for the storage of platelet at 4°C. The experimental results demonstrate that at 4°C, qualities of platelets stored in PAS-III is inferior to that of platelets stored with plasma. In the research, several factors are added to the PAS-III to find the factors useful to 4°C storage of platelets. Except for dextrose, other factors added in the PAS-III were beneficial for the storage of platelets. Combining these factors, GMA was used to store platelets, and GMA-PCs and PAS-III-PCs were compared. The results demonstrate that the in vitro qualities such as MPV, pH, HSR, P-selectin and IL-6 were superior to those of PAS-III-PCs. It shows that compared with PAS-III, GMA is more suitable for storage of platelets at 4°C.To confirm the ratio of plasma in platelet additive solution, the solutions containing different plasma ratio were compared to evaluate in vitro quality of platelets stored. The results showed that 35% ACD plasma was sufficient to provide the physiological environment and metabolism energy. Based on the results, the concentration of K+ was adjusted, and dextrose was removed, and a platelet additive solution PAS-R₁ was formed. Finally, a comparison was made between the platelets stored in the PAS-R₁ at 4°C and those stored with routine procedures at RT. The results showed that there were no significantly differences between PAS-R₁-PCs and PAS-III-PCs in the in vitro qualities such as platelet count, pH, MPV, P-selectin, PS, HSR and ESC, yet the content of lactic acid PAS-R₁-PCs was less than PAS-III -PCs. It showed that PAS-R₁-PCs can be the elementary platelet additive solution for storage of platelets at 4°C.In addition, to investigate the mechanisms of rapid clearance of refrigerated platelets from the circulation, THP-1 cell was used to investigate the roles for exposed PS and GPIba in phagocytosis, and phagocytosis of platelets stored in plasma and the platelet additive solution at 4°C by THP-1 cells was also compared to make sure that the platelets stored in the platelet additive solution PAS-R₁ would not be inferior to those stored in plasma at 4°C in terms of the rapid clearance of platelets, and the intensity of GPIba in the platelet plasma was related to the phagocytosis of platelet in vitro, however, there was no relation between the expression of PS on platelet membrane and the clearance of refrigerated platelets in short time of storage. These results defined the clearance mechanism of chilled platelets elementarily, and provide the basis for storage of platelets at 4°C.