Viability of platelets following storage in the irradiated state. A pair-controlled study

Gamma irradiation of blood products is a standard practice recommended for the prevention of posttransfusion graft-versus-host disease in susceptible hosts. We studied the effects of irradiation on stored platelet concentrates and evaluated whether platelets could be stored for 5 days in the irradiated state without adverse effects on their viability. Using a pair-controlled design in which each of six normal subjects acted as his or her own control, we compared in vitro storage characteristics and in vivo kinetics of platelet concentrates exposed to 30 Gy and stored for 5 days with those of platelet concentrates simply stored for 5 days without irradiation. Irradiation had no significant effects on in vitro storage characteristics (platelet count, mean platelet volume, pH, and white cell count) or on in vivo kinetics, including initial recovery and mean platelet survival. Using the multiple-hit model, initial recovery was 49.6 +/- 10.8 percent, and mean platelet survival was 5.6 +/- 1.05 days for irradiated concentrates, compared with 51.3 +/- 13.0 percent and 5.9 +/- 0.50 days, respectively, for the unirradiated control concentrates. We conclude that irradiation of platelet concentrates with up to 30 Gy has no effect on their in vivo recovery or survival, and that irradiation administered before storage of platelet concentrates does not interfere with their clinical efficacy.     

Platelet concentrates stored for 5 days in a reduced volume of plasma maintain hemostatic function and viability

BACKGROUND: Platelet concentrates prepared from whole blood are generally suspended in a standard volume of 50 to 60 mL of plasma and can be stored thus at 20 to 24 degrees C for up to 5 days. In vitro studies suggested that this plasma volume could be reduced to 30 to 35 mL without impairing platelet function. STUDY DESIGN AND METHODS: This study evaluated whether platelets stored for 5 days in a reduced volume (30-35 mL) of plasma maintained their in vivo viability, hemostatic function, and recovery in recipients. Paired autologous platelet survival studies were done in 20 adult volunteers to assess platelet viability. A rabbit ear bleeding-time model was used to compare the hemostatic effectiveness of human platelet concentrates stored for 5 days in the standard or reduced volume of plasma. Platelet recovery was compared in thrombocytopenic hospital patients. RESULTS: Paired platelet survival studies indicated no significant difference between the values in platelet concentrates stored for 5 days in the reduced volume of plasma and the values in those stored in the standard volume. In the animal model, there was no significant difference in the bleeding times achieved by either set of platelet concentrates. The platelet count increments in thrombocytopenic patients were measured. The platelet count increments in patients who received reduced-volume platelet concentrates were as good as the increments achieved in patients given standard-volume concentrates. CONCLUSION: The in vivo viability, recovery, and hemostatic function of platelets collected in polyvinylchloride plastic containers and stored in 30 to 35 mL of plasma for 5 days are maintained as well as those of platelets stored in 50 to 60 mL of plasma.     

Ultraviolet-B irradiation of platelets: a preliminary trial of efficacy

Prior studies established that ultraviolet-B light (UVB) irradiation of platelet concentrates (PCs) at appropriate doses can eliminate the mixed lymphocyte culture-stimulating and -responding capacity of lymphocytes in the PCs without adversely affecting in vitro platelet function. The in vivo recovery and survival and in vitro characteristics of UVB-irradiated platelets were investigated in paired studies. PCs were stored for 1 day and then exposed to UVB. Platelet recovery, survival, and function were comparable to those of nonirradiated platelets. Recovery and survival of platelets stored for 5 days before UVB exposure were decreased relative to controls, although they were considered clinically acceptable. Paired transfusion studies were also performed in seven thrombocytopenic patients by using platelets obtained by apheresis. Comparable posttransfusion platelet increments and bleeding time corrections were obtained with both irradiated and control (nonirradiated) platelets. It can be concluded that platelets survive and function relatively normally in vivo after UVB irradiation sufficient to abolish lymphocyte reactivity in mixed lymphocyte culture. Long-term studies of UVB-irradiated PCs are needed to assess their potential in reducing recipient alloimmunization.     

Resistance of platelet proteins to effects of ionizing radiation

Gamma irradiation of blood components prevents lymphocyte-induced graft-versus-host disease after transfusion in immunocompromised individuals. In this report we demonstrate the resistance of blood platelet proteins to gamma radiation-induced protein cleavage and aggregate formation when platelet concentrates were treated with a dose of 5000 rad. Results of one- and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total platelet protein and cytoskeletal protein preparations indicate that platelet proteins are neither cleaved nor cross-linked under these conditions of irradiation. These results support those of a previous study that documented the lack of any adverse effect of 5000 rad gamma radiation on in vitro platelet properties.     

Platelet function testing during 5-day storage of single and random donor plateletpheresis.

Platelet concentrates are routinely manufactured from whole blood by differential centrifugation (random donor platelets-RDP) or by plateletpheresis (single donor platelets-SDP). These platelet concentrates have a storage period of 5 days and many different approaches exist to measure the condition of platelets during their storage. In this study, platelet aggregation testing using adenosine diphosphate (ADP) and collagen and flow cytometric platelet activation analysis using CD41 FITC and CD62 PE before and after ADP was performed on days 1, 3 and 5 of storage of platelet preparations. Thirty three RDPs, stored in Baxter and Kansuk blood bags and 18 SDPs stored in Fresenius blood bags were evaluated. In RDPs and in SDPs; ADP and collagen induced PA responses were decreased significantly on the 3rd and 5th days compared to 1st day. CD62 positive platelet percentage after ADP were decreased significantly on the 3rd and 5th days compared to the 1st day in Kansuk((R)) bags. Flow cytometric analysis revealed minor changes in CD41 expression after ADP on the 3rd day compared to 1st day and on the 5th day compared to 3rd day. Differences in CD62 positive platelet percentage were not significant between the RDPs and SDPs. Our results suggest that: (1) ADP and collagen induced PA responses decrease both in RDPs and SDPs during storage. (2) Flow cytometric analysis does not show major significant changes in platelet activation after ADP during storage. (3) Continous shaking on the agitator does not cause a significant change in CD62 positive platelet percentage during storage. (4) Platelet aggregation responses in RDPs stored in Baxter((R)) and Kansuk((R)) blood bags do not differ during storage.     

Extension of platelet concentrate storage

Extension of the storage time of platelet concentrates in a satellite bag which is part of a new blood bag system was studied by reinfusing autologous 51Cr-labeled platelets into normal volunteers, and measuring postinfusion platelet counts and bleeding times in patients requiring platelet transfusions. This satellite bag, made of polyvinylchloride plasticized with a new agent, was found to protect platelet concentrates against fall of pH better than other containers studied. This protection was felt to be due to the greater gas permeability of the new plastic. Mean in vivo recovery and half-life (greater than 31% and 3.3 days, respectively) of autologous reinfused platelets were satisfactory following 5 days of storage. Following 7 days of storage, mean recovery was 41 percent and half-life was 2.8 days. Peripheral platelet count increments in patients following platelet transfusions with concentrates stored 4 to 7 days in the new plastic were comparable to increments following transfusion of platelets stored 2 to 3 days in the other plastics studied. Bleeding times shortened in three of four patients receiving platelet concentrates stored from 4 to 6 days in the new plastic. Platelet concentrates stored in the new bag at 20 to 24 degrees C with flat-bed or elliptical agitation could be transfused for up to 5 days following phlebotomy with acceptable clinical results. The new plastic container is promising for storage of platelet concentrates for up to 7 days. Due to the higher pH of 50-ml platelet concentrates stored in bags made with the new plastic, the concentrates were superior at any storage interval to those stored in bags made of the other plastics studied.     

Autoapheresis and intraoperative blood salvage in oncologic surgery

Platelet activation occurs during the collection, processing and storage of platelet concentrates. The effect of the platelet activation on the functional state of stored platelets remains however undefined. We employed flow cytometric analysis to evaluate the extent of platelet activation and the physiological response to thrombin stimulation of platelets stored for up to five days under routine blood bank conditions. Platelet surface expression of the activation markers CD62 and CD63 was examined, along with modulation of platelet membrane glycoproteins (GP) Ib and IIbIIIa. Platelet dense granule content was determined using a mepacrine uptake assay and the extent of platelet microparticle generation was quantified. Thirteen random-donor platelet concentrates prepared under routine conditions by a platelet-rich-plasma protocol were examined. Platelets were found to be activated following preparation on day 1. Although a gradual increase was seen with increasing storage time, this was not statistically significant for CD62 or CD63 expression, GPIIbIIIa or GPIb modulation or dense granule release; the generation of platelet microparticles did, however, increase with increasing storage time. The characteristic increase in surface expression of CD62, CD63 and GPIIbIIIa and decrease in GPIb and dense granule content in response to thrombin stimulation was observed with all concentrates, but these measures of platelet functional reserve showed decreasing platelet function with increasing storage time. The results indicate that platelets are activated by day 1, likely as a consequence of manipulation during collection and processing, but are not further progressively activated with increasing storage time; they do, however, become relatively hypofunctional with increasing storage.     

Effect of gamma radiation on the in vitro aggregability of WBC-reduced apheresis platelets

BACKGROUND: The effect of gamma radiation on single-donor apheresis platelet concentrates (SDPs) has been elucidated only incompletely. The only existing report on the function of SDPs stored in the irradiated state found a deterioration in the in vitro aggregability at the end of shelf life in SDPs divided before irradiation with 1500 cGy. STUDY DESIGN AND METHODS: The in vitro properties of platelets were examined in four series of irradiated and control platelets, each obtained from the same 15 donors. Irradiation with 3000 cGy was performed on Days 0, 3, and 5. Cellular content, aggregability by ADP alone or ADP and epinephrine, spontaneous and induced CD62 expression, beta-thromboglobulin release, glucose consumption, lactate production, and pH were measured immediately after preparation and on Days 3 and 5 after donation. RESULTS: Comparable in vitro properties were measured in irradiated and control platelets, whether irradiation was performed on Day 3 or Day 5. However, in platelets irradiated on Day 0, we found a significantly better in vitro aggregability by 20 microM: ADP immediately after irradiation and by 10 microM: ADP and 2 microM: epinephrine at the end of shelf life than was found in the other groups (Day 5 results: Day 0 irradiation: 75 +/- 32%; Day 3 irradiation: 45 +/- 45%; Day 5 irradiation: 47 +/- 41%; control: 40 +/- 24%; p<0.05). CONCLUSION: Gamma radiation had no adverse effect on platelet quality in extremely WBC-reduced SDPs. On the contrary, a slight, but significantly better in vitro aggregability was found in SDPs irradiated before storage than in platelets irradiated later during storage and in unirradiated platelets. This increased in vitro aggregability persisted until the end of shelf life.     

Reduction of the volume of stored platelet concentrates for use in neonatal patients

Premature infants and neonatal patients who require platelet transfusions may develop circulatory overload when administered a 50-ml unit of platelet concentrate. We evaluated the influence of centrifugation and resuspension steps used to reduce the volume of stored platelet concentrates on platelet properties by in vitro methods and by determining post-transfusion increments in neonatal patients. In vitro studies were conducted with platelet concentrates stored at 20 to 24 degrees C for 1 and 5 days in CLX (Cutter) and PL732 (Fenwal) containers and for 1 and 2 days in PL146 containers (Fenwal). With platelets stored in any of the three containers, platelet morphology, mean platelet volume, hypotonic stress response, synergistic aggregation, and platelet factor 3 activity were not affected by the processing steps. The centrifugation and resuspension steps did not cause an enhanced discharge of lactate dehydrogenase from platelets. Similar results were obtained when the platelet concentrates were stored on either a flatbed or an end-over-end tumbler agitator. The in vitro platelet recovery following volume reduction was at least 85 percent. In vivo studies were conducted with platelets stored in the PL732 and PL146 containers. Infusion of platelet concentrates after volume reduction produced a mean corrected increment of 18,947 +/− 14,824 when platelets were stored in the PL146 container and 16,178 +/− 15,699 when platelets were stored in the PL732 container. These results indicate that the volume of stored platelet concentrates can be reduced in a manner which maintains platelet properties.     

Plasmin activity and complement activation during storage of citrated platelet concentrates

Platelet concentrates were studied for evidence of plasmin activity and complement activation during a 7-to-10-day storage period. When measured by an amidolytic activity assay, plasmin reached a level of 845 +/- 540 nkats/L on day 7 (n = 9). Fibrin(ogen) degradation product (FDP) levels became markedly elevated on the tenth day of storage, rising to 45 +/- 22 micrograms/ml (n = 5). Antiplasmin levels decreased in platelet concentrates by 18% +/- 6% (n = 5) over 7 days, but there was no significant decrease in stored platelet-poor plasma (-1.7%, n = 5, p = 0.5). The amount of plasminogen in platelet concentrate converted to plasmin was estimated to be less than 3% by assay of total plasminogen. Supernatant plasma from stored platelet concentrates was examined for the presence of the complement activation peptides C3a and C5a. From day 0 to day 10 of storage, mean C3a levels rose from 327 ng/ml to 6690 ng/ml. An equivalent increase in C3a levels, from 336 ng/ml at day 0 to 6866 ng/ml at day 10, was also observed in stored platelet-poor plasma. C5a was not detected (less than 10 ng/ml) at any point during the storage period; however, we noted a small decrease of borderline significance (p = 0.04) in total C5 from day 0 (117 micrograms/ml) to day 10 (108 micrograms/ml). Only trace amounts of C3 fragments were found on stored platelets, and there was no evidence of the membrane attack complex. These findings indicate the presence of plasmin activity and conversion of C3 during storage of platelet concentrates.     

The effect of storage on platelet morphology

Platelet concentrates were stored for one, two or three days at 4 degrees C (unagitated) or at room temperature (unagitated and linearly agitated). After washing the concentrates twice at room temperature and then incubating them for 60 minutes at 37 degrees C, the platelet morphology was investigated by scanning and transmission electron microscopy. Platelets in freshly prepared concentrates were slightly activated, indicated by some pseudopod formation. Platelets stored at 4 degrees C rapidly lost the normal discoid shape. After three days of storage their surface membranes showed extensive folding, they were slightly vacuolated, and had lost most of their granules. Incubation of cold-stored platelets at 37 degrees C did not induce return to the discoid shape. Room temperature storage resulted in reversal of the slight initial platelet activation. After three days of unagitated room temperature storage the platelets were slightly more vacuolated than those stored with agitation. Room temperature storage usually resulted in well-preserved discoid platelets; however, some agitated platelet concentrates stored at room temperature contained a high proportion of odd shaped cells. This finding could not be correlated with pH change. The failure of platelets stored at 4 degrees C to return to the discoid shape after incubation at 37 degrees C could explain their short survival following transfusion. These results also provide a morphologic correlation with the reported slightly better recovery and survival of platelets stored at room temperature with agitation compared with those stored without agitation.     

The effect of obstruction of bag surface on platelet concentrate pH

Platelet concentrates stored in bags (made of a plastic film incorporating a new plasticizer) on flat-bed agitators for up to 5 days were found to have accelerated pH decline when the surface of the bag was obstructed with added labels and an invoice on the non-labeled side. Without the over-labeling and invoice, only one of 20 concentrates had a pH below 6.0, even at very high concentrations of platelets. Blood banks experiencing problems with pH decline in the platelet concentrates being stored up to 5 days should consider eliminating surface obstruction on the bag.     

Phosphatidylserine exposure in platelet concentrates during the storage period: differences between the platelets collected with different cell separators.

BACKGROUND AND OBJECTIVES: Platelet alterations occur during the production and storage of platelet concentrates, the so called "storage lesion". We studied the platelet alterations during the storage period in apheresis concentrates, employing flow cytometry for phosphatidylserine (PS) detection on platelets during the five days of storage. MATERIAL AND METHODS: Twenty-seven single donor platelet concentrates harvested with the Cobe Trima, Baxter Amicus, or Haemonetics MCS+ were analyzed for PS exposure by flow cytometry on the day of production (day 1) and on days 3 and 5 of storage. Furthermore PS expression was analyzed in platelet donors' blood samples withdrawn before plateletpheresis. RESULTS: PS expression on platelets gave the following median values: in blood donors before apheresis it was 1.12% (0.13-1.78) in platelets concentrates on the first day (2 h after apheresis) 2.06% (0.66-15.2), the third day 6.57% (1.98-51.13) and the fifth day 23.04% (3.86-80.23). All differences between median values of PS expression in blood samples before apheresis, and platelets concentrates on days 1, 3 and 5 of storage, are statistically significant. The expression of PS in platelet concentrates was analyzed in relation to the blood cell separator used for the collection procedure and showed the following results: on day 1 the median values of PS in platelet concentrates collected with the three different blood cell separators, Trima, Cobe and MCS, did not show statistically significant differences. On day 3, the platelets concentrates collected with the Trima and with the MCS showed differences that were statistically significant. Those were respectively 10.59% (4.56-51.13) and 3.53% (1.98-12.61), p = 0.005. The PS expression in platelet concentrates collected with the Trima and MCS showed differences that are also statistically significant on day 5 at respectively 32.4% (9.61-80.23) and 8.57% (3.86-48.42), p = 0.005. CONCLUSIONS: PS exposure in platelet concentrates on days 3 and 5 rise to levels that could compromise the quality of the platelet units. Improvements in standardized platelet quality controls, and in platelet collection systems are required to reduce the storage lesions in platelets concentrates.     

Storage of apheresis platelets after gamma radiation

BACKGROUND: There are conflicting data on the effect of irradiation and subsequent storage on the quality of platelet components. STUDY DESIGN AND METHODS: The retention of platelet properties during storage of gamma-irradiated apheresis suspensions was studied in 22 apheresis components obtained on a cell separator with a specialized centrifugation chamber. Immediately after collection, each suspension was divided equally into two 1-L polyolefin containers. On Day 1 (n = 12) and Day 3 (n = 10) one of each pair of suspension containers was gamma radiated with 2500 cGy. All platelet suspensions were stored for 5 days at 20 to 24 degrees C. Samples were drawn on Day 5 from each of the 22 pairs of containers for evaluation of an array of in vitro properties. Samples were taken from 10 pairs of containers for platelet labeling with either 51Cr or 111In for subsequent transfusion and concurrent in vivo measurement of recovery and survival. Posttransfusion samples were drawn after 24 hours for ex vivo whole blood aggregation. RESULTS: Comparable in vitro and in vivo properties were measured in irradiated and control platelets, whether irradiation was performed on Day 1 or Day 3. The mean +/− 1 SD in vivo recovery and survival time for controls and platelets irradiated on Day 1 was 52 +/− 14 percent and 146 +/− 34 hours and 51 +/− 7 percent and 147 +/− 36 hours, respectively. For Day 3 irradiation, the values were 46 +/− 12 percent and 150 +/− 60 hours and 47 +/− 9 percent and 151 +/− 53 hours, respectively. A small, but measurable adverse effect of irradiation on ex vivo platelet aggregation was present. CONCLUSION: These data indicate that storage of apheresis platelets after gamma radiation is without clinically significant, demonstrably adverse effects on platelet quality.     

Apoptotic activity in stored human platelets

BACKGROUND: Platelets possess some of the machinery required for apoptotic cell death. However, disruption of mitochondria function, implicated in several models of cell death, has not been extensively studied in platelets. Mitochondrial viability and several other measures of apoptotic death in stored and experimentally stressed platelets were evaluated. MATERIALS AND METHODS: Platelet mitochondrial transmembrane potentials (Deltapsim) were studied by staining platelets with JC-1, a dye that fluoresces at different wavelengths based on the state of mitochondrial polarization. Annexin V binding, a measure of phosphatidylserine (PS) exposure, and CD62P expression, an indicator of platelet activation, were determined by flow cytometry. Caspase-3 activity was measured with an enzyme assay and by Western blotting. Experimental platelet stressors included storage for 7 days, azide exposure, calcium ionophore stimulation, and plasma deprivation. RESULTS: As measured by flow cytometry, Deltapsim values were similar in freshly drawn platelets and in platelet concentrates stored for up to 7 days. However, compared to fresh platelets, stored platelet concentrates had significantly increased PS exposure (3.1 vs. 5.1%, p = 0.015), CD62P expression (6.5 vs. 13.5%, p = 0.0067), and caspase-3 activity. Azide exposure, which decreased ATP release 20 to 30 percent, did not affect the Deltapsim. Stressed platelets exhibited higher degrees of mitochondrial depolarization in response to calcium ionophore stimulation than platelets that were not stressed. Plasma deprivation also resulted in significant alterations in Deltapsim, PS exposure, and CD62P expression. CONCLUSIONS: Platelet mitochondria maintain Deltapsim when stored for up to 7 days under standard blood bank storage conditions. Therefore, changes in platelet mitochondria Deltapsim do not correlate with downstream markers of apoptotic death such as caspase activation and PS exposure.     

Storage of human platelet concentrates in an artificial medium without dextrose

It was shown previously that human blood platelets stored in an artificial medium (PCD) for up to 5 days remain functional in vitro and have normal survival and recovery in vivo. This report demonstrates that the medium can be simplified further by the removal of dextrose, leaving for study a medium consisting simply of balanced salts and citrate anticoagulant (PC). Some dextrose, 3.2 mM, was present in the fresh PC platelet concentrates due to plasma carryover in the production of platelet concentrates, but this dextrose concentration was considerably less than the 22.6 to 25.5 mM present in platelet concentrates in PCD or plasma. Platelet count, pH, PCO2, and PO2, as well as platelet aggregation and release responses to stimulation, in vitro, were as well preserved in the PCD or PC media as in the plasma controls. In the PC medium, platelets consumed 2.5 mM dextrose over 5 days and left 0.7 mM dextrose. The same consumption of dextrose was noted in PCD platelet concentrates, while platelets in plasma metabolized twice as much dextrose and formed twice as much lactate. Thus, the rate of glycolysis in platelet concentrates was independent of the dextrose concentration in the medium, and the platelet functions were well preserved.     

Platelet viability following storage for 5 days. Influence of holding whole blood for 8 hours at 20 to 24 degrees C before concentrate preparation

Regional blood centers frequently need to hold units of whole blood at 20 to 24 degrees C for several hours after phlebotomy so that sufficient platelet concentrates can be prepared to meet the increasing need. We have evaluated the in vivo viability and in vitro properties of platelets that were prepared from whole blood drawn into citrate- phosphate-dextrose-adenine (CPDA-1) either immediately after phlebotomy or after an 8-hour hold at 20 to 24 degrees C. Platelet concentrates were stored for 5 days at 20 to 24 degrees C in polyolefin containers (PL 732, Fenwal) with end-over-end tumbler agitation. The autologous in vivo recovery (mean +/− SD) and one-half disappearance of 51Cr-labeled platelets prepared immediately after phlebotomy were 44.4 +/− 9.4 percent and 4.0 +/− 0.5 days, respectively. Platelets prepared after the delay of 8 hours showed a recovery of 44.5 +/− 8.4 percent and a one-half disappearance of 4.1 +/− 0.4 days. After 5 days of storage, platelet concentrates showed a mean pH of 7.21 +/− 0.20 when prepared immediately after phlebotomy, and of 7.22 +/− 0.15 when prepared after an 8-hour delay. Mean morphology scores were 280 +/− 33 and 302 +/− 27 for platelets from units prepared immediately after phlebotomy or after a holding period of 8 hours, respectively. Platelets underwent synergistic aggregation after 5 days of storage, independent of the length of time that the units of whole blood were held prior to centrifugation. These studies indicate that platelet concentrates prepared from units of whole blood held initially for 8 hours can be stored for 5 days at 20 to 24 degrees C and survive satisfactorily in vivo and retain in vitro characteristics.     

Platelet apoptosis and activation in platelet concentrates stored for up to 12 days in plasma or additive solution

Background: Several studies suggest that apoptosis of platelets occurs during storage of platelet concentrates (PC). We sought to determine whether storage of PC in additive solution alters levels of apoptosis during storage beyond the current shelf life (5–7 days). Study design and methods: Pooled buffy coat PC (n = 7) were prepared in either 100% plasma or 70% Composol and stored at 22 °C for 12 days. A third arm of the study stored PC in 100% plasma at 37 °C, which is thought to induce apoptosis. PC were tested for mitochrondrial membrane potential, annexin V binding, microparticles, caspase‐3/7 activity and decoy cell death receptor 2, as well as standard platelet quality tests. Results: Composol units remained ≥pH 6·88, with 36% lower lactate and higher pH vs plasma by day 12 (P < 0·001). Platelet function was better maintained, and activation and apoptotic markers tended to be lower in Composol units towards the end of storage. However, levels of all apoptosis markers assessed were not significantly different in units stored in Composol. Storage at 37 °C saw stronger correlation of apoptotic markers with standard quality tests compared to 22 °C, but loss of correlation of caspase‐3/7 activity with other apoptosis markers. Conclusion: We conclude that storage of platelets in 70% Composol vs 100% plasma does not increase the rate of platelet apoptosis. Our data agree with other studies suggesting that platelet apoptosis is sequential to high levels of activation, but share a significant degree of overlap.     

Platelet storage in a plasma-free medium

Currently, platelet concentrates are stored in 50 to 60 ml of plasma. A major drawback to storage in plasma is the considerable loss of platelet function which occurs during storage. A modified Tyrodes medium has been developed for storage of platelets. A comparison between platelet concentrates stored in this medium and in plasma showed that platelet aggregation and release responses to synergistic pairs of stimuli were equivalent for both types of concentrates on the day of preparation and after 72 hours. Platelet aggregation and release responses to single stimuli, the content of membrane glycoproteins, and the pH declined during storage but were similar for both preparations. The data show that plasma is not required to maintain in vitro platelet function during storage of platelet concentrates, but in vivo functions remain to be determined. The use of an artificial medium has the advantages of decreasing patient exposure to plasma contaminants, generating additional plasma for fractionation, and controlling more exactly the storage environment.     

Platelet storage at 22°C; metabolic, morphologic, and functional studies

Platelets stored at 22 degrees C for transfusion purpose have been examined with metabolic, morphologic, and functional studies. Evaluations were made of platelet-rich plasma (PRP) stored for 3-4 days and platelet concentrates (PC) stored for 24 hr. During these periods, lactate accumulated continuously without significant change in platelet count, pH, or plasma glucose. Platelet glycogen fell dramatically both chemically and by electron microscopy, but adenosine triphosphate (ATP), adenosine diphosphate (ADP), and intracellular potassium did not change. After storage, the cell's capacity for glucose utilization through glycolysis, the hexose monophosphate shunt, and the tricarboxylic acid cycle appeared to be intact. Although platelet volume during storage did not change, disc to sphere transformation was observed by phase microscopy. Platelet aggregration with ADP was reduced even after 1 day of storage. After transfusion of stored platelets to thrombocytopenic recipients, recovery of platelet glycogen and capacity for aggregation occurred within 24 hr. In summary, the platelet remains surprisingly intact during the intervals studied; those defects which do develop are reversible in the circulation of a thrombocytopenic recipient if viability has been maintained. A "storage lesion" responsible for loss of viability has not been defined.