In vitro platelet function during storage in three different additive solutions

The platelet storage lesion

The continuous increase in the demand for platelet transfusion has necessitated the need to establish standards for determining the quality of platelets during storage. Bacterial contamination of platelet products and deleterious changes in structure and function referred to as the platelet storage lesion (PSL), have restricted the platelet shelf life to 5 days. The PSL and platelet health variables have been well studied and documented. The precise correlation between in vitro assays and in vivo platelet recovery and survival is yet to be established. This review presents an overview of the current understanding of PSL and the novel approaches being developed to negate the storage lesion.

In vitro function of buffy coat-derived platelet concentrates stored for 9 days in CompoSol, PASII or 100% plasma in three different storage bags

BACKGROUND AND OBJECTIVES

The aim of the study was to compare the in vitro quality of buffy coat-derived platelet concentrates (PC) during extended storage in plasma or additive solution in three different storage bags.

MATERIALS AND METHODS

A pooled and split design was chosen so that identical PCs were produced in either 100% plasma, 70% PASII : 30% plasma or 70% CompoSol : 30% plasma (n = 6 each). This was repeated for three different manufacturers' platelet storage bags (Fresenius, Baxter and Pall). PCs were sampled on days 1, 5, 7 and 9 of storage and tested in vitro using a variety of tests of platelet function. For each bag type, storage in PASII or Composol was compared with plasma (data taken across the entire storage period), and differences occurring with time were analysed for all storage media.

RESULTS

The pH of all PCs was > 6.8 at day 9 of storage. In vitro platelet function, as assessed by markers of platelet activation and metabolism, of PCs stored in CompoSol appeared to be similar to that of PCs stored in plasma over 9 days of storage. In contrast, PCs stored in PASII tended to have significantly higher levels of platelet activation (almost a twofold increase in % platelets positive for CD62P by day 5) and lower hypotonic shock response (approximately 40%, by day 7) compared to either PCs stored in 100% plasma or 70% CompoSol. The magnitude of the differences observed between platelet storage media appeared to be dependent on the type of platelet storage bag with the highest degree of platelet activation and lowest hypotonic shock response values being observed in Fresenius bags in combination with PASII.

CONCLUSIONS

The maintenance of platelet function in vitro during extended storage of PCs in platelet additive solutions is dependent on the combination of type of additive solution and type of platelet storage bag. For all bag types studied, storage in PASII resulted in poorer platelet function in vitro.

Fully automated processing of buffy-coat-derived pooled platelet concentrates

BACKGROUND

The OrbiSac device, which was developed to automate the manufacture of buffy-coat PLT concentrates (BC-PCs), was evaluated.

STUDY DESIGN AND METHODS

In-vitro characteristics of BC-PC preparations using the OrbiSac device were compared with manually prepared BC-PCs. For standard processing (Std-PC, n = 20), four BC-PCs were pooled using 300 mL of PLT AS (PAS) followed by soft-spin centrifugation and WBC filtration. The OrbiSac preparation (OS-PC, n = 20) was performed by automated pooling of four BC-PCs with 300 mL PAS followed by centrifugation and inline WBC filtration. All PCs were stored at 22 degrees C. Samples were withdrawn on Day 1, 5, and 7 evaluating PTL count, blood gas analysis, glucose, lactate, LDH, beta-thromboglobulin, hypotonic shock response, and CD62p expression.

RESULTS

A PLT content of 3.1 +/- 0.4 x 10(11) (OS-PCs) versus 2.7 +/- 0.5 x 10(11) (Std-PCs, p < 0.05) was found. A CV of 19 percent (Std-PC) versus 14 percent (OS-PC) suggests more standardization in the OS group. At Day 7, the Std-PCs versus OS-PCs showed a glucose consumption of 1.03 +/- 0.32 micro mol per 10(9) PLT versus 0.75 +/- 0.25 micro mol per 10(9) PLT (p < 0.001), and a lactate production of 1.50 +/- 0.86 micro mol per 10(9) versus 1.11 +/- 0.61 micro mol per 10(9) (p < 0.001). The pH (7.00 +/- 0.19 vs. 7.23 +/- 0.06; p < 0.001), pO(2) (45.3 +/- 18 vs. 31.3 +/- 10.4 mmHg; p < 0.01), and HCO(3) levels (4.91 +/- 1.49 vs. 7.14 +/- 0.95 mmol/L; p < 0.001) suggest a slightly better aerobic metabolism within the OS group. Only small differences in CD62p expression was observed (37.3 +/- 12.9% Std-PC vs. 44.8 +/- 6.6% OS-PC; p < 0.05).

CONCLUSION

The OrbiSac device allows an improved PLT yield without affecting PLT in-vitro characteristics and may enable an improved consistency in product volume and yield.

Implementation of the INTERCEPT Blood System for Platelets into routine blood bank manufacturing procedures: evaluation of apheresis platelets

BACKGROUND AND OBJECTIVES

The INTERCEPT Blood System for Platelets utilizes amotosalen-HCl (S-59) in combination with ultraviolet A (UVA) light to inactivate viruses, bacteria, protozoa and leucocytes that may contaminate platelet concentrates (PCs). To facilitate implementation of this technique into routine blood bank manufacturing procedures, this study evaluated the impact of different time settings of photochemical treatment on in vitro platelet function.

MATERIALS AND METHODS

Platelets derived from apheresis (6.5-7.0 x 10(11) platelets) were resuspended in 240 ml of autologous plasma and 360 ml of platelet additive solution (PAS III) and split into two equal-sized PC units. Whereas one unit was not treated, the other was treated with 150 microm amotosalen and 3 J/cm2 UVA light followed by a compound adsorption device (CAD) step for reduction of residual amotosalen and photoproducts. In a first series of experiments (arm A, n = 7), PC units were photochemically treated after an overnight storage period of 16-23 h followed by a CAD step of 4 h. In a second series (arm B, n = 8), photochemical treatment occurred after a short storage time of 4 h with a subsequent CAD step of 16 h. Platelet function was evaluated by assaying blood gas analysis, glucose and lactate concentration, lactate dehydrogenase (LDH), hypotonic shock response (HSR) and the expression of CD62p, over a period of 7 days.

RESULTS

Neither of the photochemical treatment procedures showed differences for pH, pCO2, pO2, HCO3, glucose consumption or platelet activation until the end of day 7. Increased lactate values detected for the treated units of arm A at the end of the storage period were independent from the PCT time setting.

CONCLUSIONS

Photochemical pathogen inactivation with different initial resting periods between 4 and 23 h, and different CAD steps of 4 and 16 h, had no influence on the platelet in vitro function during 7 days of storage.

Functional characteristics of buffy-coat PLTs photochemically treated with amotosalen-HCl for pathogen inactivation

BACKGROUND

One blood system for PLTs (INTERCEPT, Baxter Transfusion Therapies) is based on photochemical treatment (PCT) with small molecules that target cross-link nucleic acids (Helinx technology, Cerus Corp.) with amotosalen-HCl (S-59) and UVA light (320-400 nm) to inactivate pathogens and WBCs.

STUDY DESIGN AND METHODS

A two-arm in vitro study was conducted to compare pooled buffy-coat-derived PLT concentrates (PCs) treated with the INTERCEPT blood system, resuspended in PLT additive solution (PAS) III (InterSol, Baxter Transfusion Therapies), and stored for up to 7 days (test units, n = 20) with unpaired, nontreated PCs, resuspended in PAS II (T-Sol, Baxter Transfusion Therapies), and prepared at the same center in the same manner (control units, n = 18).

RESULTS

PLT dose (x 1011/unit +/- SD) on Day 1 immediately following PCT was 3.0 +/- 0.4 for test units and 3.2 +/- 0.4 for control units. After 7 days of storage, the pH of all test units was maintained above 6.8. No marked trend was observed in the hypotonic shock response (HSR). Values among study groups were similar at the end of observation period: 68 +/- 11 percent for control unites versus 67 +/- 8 percent for test units (p > 0.05). Aggregation response to ristocetin was slightly lower in test units: at Day 7, 65 +/- 10 percent versus 76 +/- 6 percent (p < 0.05). Significantly higher (p < 0.001) glucose consumption, lactate production, and CD62P expression were observed in test units.

CONCLUSION

Compared to nontreated PLTs, the PCT process was associated with a variety of differences of in vitro analyses. Although significant, these changes were relatively small in most cases. Characteristics correlated with survival in vivo such as HSR and swirling were comparable between both study groups, indicating that the viability of the majority of cells appears to have persisted throughout 7 days of storage. The impact of this finding, however, remains to be investigated in clinical trials performed with 7-day stored PLTs.

Post-operative course of coronary artery bypass surgery patients who pre-donate autologous blood

BACKGROUND

Pre-operative autologous blood donation is used to reduce the need of allogeneic blood in patients undergoing coronary bypass surgery operations, but it is not clear what impact the blood donation has on the post-operative course of these patients.

METHODS

We studied the post-operative course of 210 patients who pre-donated autologous blood before their coronary bypass operation (donors) and of 67 patients who were eligible to pre-donate but did not (controls).

RESULTS

The clinical variables and the technical operative parameters of the patients in the two groups were similar. There was no significant difference between the duration of assisted ventilation post-operatively (756 +/- 197 vs. 802 +/- 395 min; P=0.54) or length of stay in the intensive care unit (1.8 +/- 1.1 vs. 1.7 +/- 0.9 days; P=0.52) of the two groups. The number of autologous units of packed red cells and of fresh frozen plasma (FFP) received by the donors was significantly higher than the number of units of allogeneic packed red cells (1.5 +/- 0.9 vs. 0.3 +/- 0.9; P=0.001) and the units of homologous FFP received by the controls (2.3 +/- 0.8 vs. 0.6 +/- 1; P=0.001).

CONCLUSIONS

We found no evidence that autologous blood donation exerted a negative influence on the post-operative course of patients undergoing coronary bypass surgery. Patients who pre-donated blood received no allogeneic blood products, but the number of autologous blood products received by donors was higher than the number of blood products received by patients who did not pre-donate.

Ultrastructural changes and activation differences in platelet concentrates stored in plasma and additive solution

BACKGROUND

The aim of this study was to demonstrate how ultrastructural morphology of platelets stored in different media correlate with the appearance of particular activation markers on their cell surface.

STUDY DESIGN AND METHODS

Concentrates of buffy coat-derived platelets were stored in plasma or a glucose-free citrate-acetate-NaCl platelet additive solution (PAS2, Baxter Healthcare Corp.). Activation markers on platelets were measured by flow cytometry and compared with changes in the platelet cell surface as demonstrated by electron microscopy. Levels of the vasoactive cytokines vascular endothelial growth factor (VEGF) and RANTES (regulated upon activation, normal T-cell expressed and secreted) were determined in the storage medium of the platelet concentrate.

RESULTS

The activation markers CD62P and CD63 and the binding of thrombospondin measured by flow cytometry were expressed to a higher extent in the PAS2 group compared with the plasma group. The difference reached significance on Day 3 (CD62P: 66.37 +/- 2.44 vs. 37.83 +/- 2.03, p < 0.001; CD63: 42.11 +/- 3.29 vs. 34.84 +/- 2.04, p < 0.05; and thrombospondin binding: 18.84 +/- 3.9 vs. 13.98 +/- 3.87, p < 0.001, respectively). The form factor that is related to changes of the platelet shape was determined by image analysis and correlated significantly with the cell surface expression of CD62P (p < 0.001) and with CD63 (p < 0.05) and with thrombospondin binding (p < 0.05). The chemokines VEGF and RANTES were measured at higher levels in the PAS2 group.

CONCLUSIONS

With exception of baseline activation probably due to necessary handling procedures, platelets remain relatively unaltered and more stable in plasma in comparison to storage in PAS2.

Thrombopoietin and the TPO receptorduring platelet storage

BACKGROUND

For most cells, the addition of a specific growth factor has improved cellular viability by preventing programmed cell death (apoptosis). To determine whether the platelet-specific hematopoietic growth factor thrombopoietin (TPO) might improve platelet viability, endogenous TPO and the platelet TPO receptor were analyzed during storage, and the effect of recombinant TPO on platelet viability was assessed.

STUDY DESIGN AND METHODS

During platelet storage, TPO stability was assessed by SDS-PAGE, TPO receptor function was measured, and the platelet TPO receptor was characterized by a (125)I-rHuTPO competitive-binding assay. A recombinant TPO, pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF), was added to platelet concentrates during storage, and its effect on pH, LDH, and metabolic activity was determined.

RESULTS

During storage, the molecular weight and concentration of endogenous TPO (125 +/- 19 pg/mL) and exogenous TPO (5720 +/- 140 pg/mL) were constant for 12 days; the number (33 +/- 4), binding affinity (149 +/- 33 pM), and function of the platelet TPO receptors were constant for 7 days. Metabolic activity measured with the MTT and MTS assays closely correlated with changes in the pH and LDH. The addition of PEG-rHuMGDF did not alter the pH, LDH, or metabolic activity of platelets during storage, but it did increase by 65 percent the uptake of (35)S-methionine into platelets. Finally, platelet concentrates obtained from donors treated with PEG-rHuMGDF retained normal metabolic activity for 12 days, as compared with 5 to 6 days for normal platelet concentrates.

CONCLUSIONS

TPO and its platelet receptor are present in normal amounts and have normal function during platelet storage. The addition of recombinant TPO increased platelet methionine transport but did not alter platelet viability during storage. Other means to prevent apoptosis during platelet storage should be considered, and the measurement of platelet metabolic activity by MTT and MTS assays may assist this effort.

In vitro analysis of platelet concentrates stored in the presence of modulators of 3',5' adenosine monophosphate, and organic anions

The storage of conventional platelet concentrates (PCs) under standard blood bank conditions is limited to five days, in part because longer storage periods lead to increasing damage in platelet integrity and functionality. The growing demand of PCs for clinical use, raises the interest to develop agents that would potentially permit a more extended period of storage. We have evaluated and compared the in vitro quality of PCs treated with: (1) Modulators of levels of cAMP (PGE1, foskolin, theophylline and isobutyl-methyl-xanthine [IBMX]); and (2) organic anions that function as alternative substrates of platelets (pyruvate and acetate). Platelet rich plasma (PRP) from pools (n = 6) of PCs was distributed into storage bags, and the agents to be tested were added, using saline as a control substance. PCs were stored at 22 degrees C with continuous agitation for up to 10 days. At 0, 5 and 10 days of storage, samples were analyzed for platelet counts, mean platelet volume (MPV), metabolic markers, and expression of glycoproteins (GPs). The addition of modulators of levels of cAMP, at the concentration used in the study, did not lead to substantial improvement in the parameters being evaluated, with respect to those in control units. The supplementation with organic anions, while not affecting the surface levels of GPs, favored the maintenance of metabolic values, such as pH, PCO2, and bicarbonate concentrations, as well as the preservation of MPV (p values < 0.05 respect to control units both at 5 and 10 days of storage). Our results indicate that while the use of modulators of levels of cAMP do not provide substantial benefit in the prevention of platelet storage lesions, organic anions have some advantageous effect in the storage promoted metabolic changes of PCs. These data might be considered when designing strategies to improve PC storage.

[New automatic test for the study of platelet response to variations in osmotic pressure: application in the evaluation of the viability of platelet concentrates]

Studying the osmotic resistance or swelling of platelets has often been suggested as a global test to assess the viability of those cells. A number of authors have also analysed the behaviour of platelets in hypotonic media by a variety of complementary methods (cell count, morphology, determinations of substances released, photometric measurement of aggregation induced by aggregating agents, etc). Most studies are currently based on the so-called "osmotic shock response" test, which measures according to time the light transmitted through platelet-rich plasma (PRP) after dilution in distilled water. In this study, the authors describe a new automated and reproducible test using slow dialysis to assess platelet osmotic resistance. The "Fragilimeter", a device initially described by the authors to characterise RBC fragility, has been adapted to the study of platelet osmotic behaviour. The variations in light transmission through a platelet suspension according to NaCl concentration are linked to the change in cellular volume and lysis and characterise the viability of the cells. The results obtained with normal platelets revealed the good reproducibility of the technique. The osmotic resistance is evaluated for two parameters: anticoagulant (citrate, EDTA) and cellular concentration. The test was applied to quality control of stored platelet concentrates for transfusion, prepared with different cell separators.

In vitro and in vivo properties of various types of platelets

The most popular procedures used to prepare platelet concentrates (PC) can be categorized into methods using platelet rich plasma (PRP) obtained by soft centrifugation of whole blood units, methods using buffy coats (BC) obtained by hard centrifugation of whole blood units, and apheresis procedures. The main feature that differentiates apheresis PC from whole blood unit derived PC is that apheresis reduces the number of donors necessary to support a recipient, although the advantages related to this feature have not been conclusively documented. From the biochemical point of view, a limited number of comparative studies and a large series of non-comparative studies indicate that differences in PC obtained with different protocols depend more on the performances of the production laboratory rather than the preparative approach--PRP, BC or apheresis--itself. Similarly, the clinical effectiveness of PC seems to depend more on PC age, storage modalities and recipient's conditions rather than primarily on the method of PC preparation. Despite the basic differences in the three preparative approaches, all methods share a number of key elements that are necessary pre-requisites for a successful platelet transfusion therapy: minimization of the risk of bacterial contamination by careful donor skin disinfection and temperature control during PC production and storage; protection of aerobic metabolism during PC storage; laboratory quality control including at least pH and volume determinations, platelet and white cell counts and visual inspection of the swirling phenomenon at time of release. Future directions in the field of PC production include the development of new products such as infusible platelet membranes, thrombospheres, thromboerythrocytes and reconstituted freeze-dried platelets.

Carbohydrate metabolism in human platelets in a low glucose medium under aerobic conditions

The metabolism of human platelets has been the subject of investigation for at least three decades, at the level of basic metabolism, and because of the increasing requirement for platelet storage. Platelets are relatively active metabolically and are typical cells in terms of fuels and metabolic pathways. They contain glycogen and utilize glucose and demonstrate aerobic glycolysis and carbohydrate oxidation. Both glycolysis and carbohydrate oxidation contribute significantly to total ATP turnover, so platelets are an ideal system in which to study the partitioning of carbohydrate metabolism between the two available fuels and the two available pathways, in the presence of adequate oxygen. We have designed a system whereby we can study carbohydrate metabolism in relatively pure human platelets, under sterile conditions, over long periods. The system enables us to determine total ATP turnover and, with the aid of a mathematical model, the contribution to this turnover of glycolysis and the oxidation of glucose/glycogen and lactate. When glucose and glycogen are present, most of the glucose and glycogen utilised is converted to lactate, but lactate is being oxidised at this time. When glucose/glycogen stores are exhausted lactate oxidation continues and increases with the result that carbohydrate oxidation accounts for 41% of total ATP turnover over 48 h.

Platelets stored in a glucose-free additive solution or in autologous plasma--an ultrastructural and morphometric evaluation

We evaluated a new glucose-free citrate-acetate-NaCl platelet additive solution (PAS 2). In series I, platelet concentrates (PC) were prepared by apheresis and subsequently stored either in plasma (n = 16) or in PAS 2 (n = 15). In series II, PCs were prepared from pools of four buffy coats (BC) and stored in plasma (n = 12) or in PAS 2 (n = 11). By means of ultrastructural morphometry, the volume fractions of alpha-granules, the open canalicular system (OCS) and the fraction of storage granules secreted into the OCS were analyzed during storage for up to 8 days. Additionally, we determined pH, glucose, lactate, pCO2, HCO3-, lactate dehydrogenase and platelet factor 4. Apheresis platelets stored in plasma showed no changes in their contents of alpha-granules and in the fractions of the OCS. In contrast, apheresis platelets stored in PAS 2 displayed a decrease of their relative volume fraction of alpha-granules from 9.1 +/- 1% on day 1 to 3.7 +/- 0.9% on day 5. The fraction of the OCS increased from 7.4 +/- 0.8% on day 1 to 17.1 +/- 1.4% on day 3. On day 8, 93 +/- 9% of all platelets were lysed. Levels of glucose were significantly lower in these preparations and after day 3 glucose consumption decreased to zero. Among PC derived from pooled BC, differences between storage in PAS 2 or plasma were less striking. Only the fraction of alpha-granules secreted into the OCS was significantly greater in BC derived PC stored in PAS 2 on all days. These PCs stored in PAS 2 had a higher plasma carryover (30%) in comparison to apheresis PC stored in PAS 2 (10%). We conclude that plasma is superior to PAS 2 for storage of both apheresis and buffy coat platelets. For preservation of the structural integrity of platelets, the use of PAS 2 requires a minimum of 30% plasma carryover.

Thrombopoietin: biology, clinical applications, role in the donor setting

Thrombopoietin (c-Mpl ligand) is the hematopoietic growth factor that is responsible for regulating the production of platelets from bone marrow megakaryocytes. This approximately 90 kd protein has recently been isolated and is comprised of an erythropoietin domain that is approximately 50% homologous to erythropoietin and a carbohydrate domain that is highly glycosylated and appears to stabilize the protein in the circulation. Thrombopoietin is produced in the liver and blood levels are determined by the mass of circulating platelets. However, there is no platelet "sensor." Rather platelets contain high affinity thrombopoietin receptors that bind and remove thrombopoietin from the circulation and thereby directly determine circulating levels. In vitro thrombopoietin stimulates both early and late megakaryocyte precursors as well as some erythroid and multipotential progenitor cells. When administered to normal animals, it stimulates platelet production up to six-fold without affecting other lineages. However, when given to animals following chemotherapy or irradiation, it stimulates erythroid and myeloid as well as platelet recovery. Several different recombinant thrombopoietin proteins are now entering clinical trials in humans and all preliminary reports confirm a potent thrombopoietic stimulus and apparent lack of toxicity. Thrombopoietin shows great promise in preventing the thrombocytopenia associated with chemotherapy, bone marrow transplantation, and other acute or chronic thrombocytopenic disorders. In transfusion medicine, thrombopoietin may help mobilize peripheral blood progenitor cells, stimulate donors for plateletpheresis, and enhance platelet survival and function during storage, Many studies are currently underway in all these areas and should soon establish the role of thrombopoietin in clinical medicine.