Cryopreservation of human platelets with dimethyl sulfoxide: changes in biochemistry and cell function

The Year in Coagulation and Transfusion: Selected Highlights from 2022

This is an annual review to cover highlights in transfusion and coagulation in patients undergoing cardiovascular surgery. The goal of this article is to provide readers with a focused summary of the most important transfusion and coagulation topics published in 2022. This includes a discussion covering the management of anemia and red blood cell transfusion, the management of factor Xa inhibitors, updates in coagulation testing, updates in the use of factor concentrates, advances in platelet therapy, advances in anticoagulation management of patients on extracorporeal membrane oxygenation and other forms of mechanical circulatory support, and advances in the diagnosis and management of heparin-induced thrombocytopenia.

Cryopreservation alters the immune characteristics of platelets

BACKGROUND

Cryopreserved platelets are under clinical evaluation as they offer improvements in shelf-life and potentially hemostatic effectiveness. However, the effect of cryopreservation on characteristics related to the immune function of platelets has not been examined.

STUDY DESIGN AND METHODS

Buffy coat derived platelets were cryopreserved at -80°C using 5%-6% dimethylsulfoxide (DMSO, n = 8). Paired testing was conducted pre-freeze (PF), post-thaw (PT0), and after 24 h of post-thaw storage at room temperature (PT24). The concentration of biological response modifiers (BRMs) in the supernatant was measured using commercial ELISAs and surface receptor abundance was assessed by flow cytometry.

RESULTS

Cryopreservation resulted in increased RANTES, PF4, and C3a but decreased IL-1β, OX40L, IL-13, IL-27, CD40L, and C5a concentrations in the supernatant, compared to PF samples. C4a, endocan, and HMGB1 concentrations were similar between the PF and PT0 groups. The abundance of surface-expressed P-selectin, siglec-7, TLR3, TLR7, and TLR9 was increased PT0; while CD40, CLEC2, ICAM-2, and MHC-I were decreased, compared to PF. The surface abundance of CD40L, B7-2, DC-SIGN, HCAM, TLR1, TLR2, TLR4, and TLR6 was unchanged by cryopreservation. Following 24 h of post-thaw storage, all immune associated receptors and TLRs increased to levels higher than observed on PF and PT0 platelets.

CONCLUSION

Cryopreservation alters the immune phenotype of platelets. Understanding the clinical implications of the observed changes in BRM release and receptor abundance are essential, as they may influence the likelihood of adverse events.

A high concentration of DMSO activates caspase-1 by increasing the cell membrane permeability of potassium

Dimethyl sulfoxide (DMSO) is widely used in the laboratory and in clinical situations because it is soluble in both aqueous and organic media and can be used to treat many types of diseases. Thus, it is meaningful to assess the comprehensive and in-depth biological activities of DMSO. Here, we showed that a high concentration of DMSO induced pro-inflammatory cytokine interleukin-1β (IL-1β) secretion from the monocytic cell line THP-1. DMSO-induced IL-1β secretion was dependent on intracellular caspase-1 activation. Further study revealed that the activation of caspase-1 by DMSO relied on NLRP3 inflammasome formation. It is generally accepted that the NLRP3 inflammasome is activated by reactive oxygen species generation or potassium efflux; however, the common NLRP3 inflammasome trigger remains controversial. Here, we showed that although DMSO is a ROS scavenger, this chemical increases membrane permeability and potassium efflux, and the formation of the NLRP3 inflammasome reflects the increased membrane permeability and potassium efflux induced by DMSO. The present study reveals a new characteristic of DMSO, which should be considered when using this chemical in either the laboratory or the clinic.

Criopreservação do plasma rico em plaquetas de equinos

Avaliou-se o congelamento do plasma rico em plaquetas (PRP) de equinos, a -196ºC em nitrogênio líquido, utilizando-se como crioprotetor o DMSO em duas concentrações (3% e 6%), e, como ponto final, a avaliação da morfologia e da agregometria plaquetária. Foram utilizadas 12 amostras de PRP em duas repetições. Previamente ao congelamento, as amostras foram submetidas a um resfriamento lento (-0,07ºC/minuto) até a temperatura final de 4-5ºC. A criopreservação do PRP equino, incluindo um resfriamento lento a 4-5ºC, previamente ao congelamento a -197ºC em nitrogênio líquido, foi similar para as concentrações do crioprotetor DMSO a 3% ou 6%, quando avaliado o percentual de ativação e de agregação plaquetária.

Review of in vivo studies of dimethyl sulfoxide cryopreserved platelets

A literature review was conducted to assess the efficacy and safety of dimethyl sulfoxide (DMSO) cryopreserved platelets for potential military use. In vivo DMSO cryopreserved platelet studies published between 1972 and June of 2013 were reviewed. Assessed were the methods of cryopreservation, posttransfusion platelet responses, prevention or control of bleeding, and adverse events. Using the Department of Defense's preferred 6% DMSO cryopreservation method with centrifugation to remove the DMSO plasma before freezing at -65°C and no postthaw wash, mean radiolabeled platelet recoveries in 32 normal subjects were 33% ± 10% (52% ± 12% of the same subject's fresh platelet recoveries), and survivals were 7.5 ± 1.2 days (89% ± 15% of fresh platelet survivals). Using a variety of methods to freeze autologous platelets from 178 normal subjects, mean radiolabeled platelet recoveries were consistently 39% ± 9%, and survivals, 7.4 ± 1.4 days. More than 3000 cryopreserved platelet transfusions were given to 1334 patients. There were 19 hematology/oncology patient studies, and, in 9, mean 1-hour corrected count increments were 11 100 ± 3600 (range, 5700-15 800) after cryopreserved autologous platelet transfusions. In 5 studies, bleeding times improved after transfusion; in 3, there was either no improvement or a variable response. In 4 studies, there was immediate cessation of bleeding after transfusion; in 3 studies, patients being supported only with cryopreserved platelets had no bleeding. In 1 cardiopulmonary bypass study, cryopreserved platelets resulted in significantly less bleeding vs standard platelets. In 3 trauma studies, cryopreserved platelets were hemostatically effective. No significant adverse events were reported in any study. In summary, cryopreserved platelets have platelet recoveries that are about half of fresh platelets, but survivals are only minimally reduced. The platelets appear hemostatically effective and have no significant adverse events.

Cryopreserved stem cell products containing dimethyl sulfoxide lead to activation of the coagulation system without any impact on engraftment

BACKGROUND

Dimethyl sulfoxide (DMSO) is extensively used as a cryoprotectant in stem cell preservation. Little is known on direct hemostatic changes in recipients of hematopoietic stem cell transplantation (HSCT), immediately after DMSO administration. The objectives of the current study were to measure hemostatic changes during HSCT.

STUDY DESIGN AND METHODS

In this prospective analysis, changes in plasma biomarkers, platelets (PLTs), or endothelial cells (D-dimers, thrombin-antithrombin complex [TAT], microparticle activity as thrombin-generation potential [MPA], whole blood aggregation, von Willebrand factor) were measured before and immediately after HSCT. Furthermore, associations with clinical complications were recorded.

RESULTS

A total of 54 patients were included in the study. Mean MPA and TAT increased significantly immediately after HSCT, returning to baseline the day after the procedure (p<0.01). No significant differences in engraftment for neutrophils and PLTs were found in patients presenting a high increase of TAT or MPA compared with those presenting with a smaller increase. Patients with a high increase in TAT and MPA had received a greater number of total mononucleated cells (p<0.001) and higher transplant volumes (p=0.002).

CONCLUSIONS

Infusion of stem cells containing DMSO reversibly activated coagulation, measured as thrombin generation. This finding was not associated with acute adverse events and did not influence engraftment. Further studies are needed to compare variable DMSO concentrations as well as DMSO-free products, to better address the influence of DMSO on hemostasis.

Membrane Stability during Biopreservation of Blood Cells

SUMMARY: Storage methods, which can be taken into consideration for red blood cells and platelets, include liquid storage, cryopreservation and freeze-drying. Red blood cells can be hypothermically stored at refrigerated temperatures, whereas platelets are chilling sensitive and therefore cannot be stored at temperatures below 20 °C. Here we give an overview of available cryopreservation and freeze-drying procedures for blood cells and discuss the effects of these procedures on cells, particularly on cellular membranes. Cryopreservation and freeze-drying may result in chemical and structural modifications of cellular membranes. Membranes undergo phase and permeability changes during freezing and drying. Cryo- and lyoprotective agents prevent membrane damage by different mechanisms. Cryoprotective agents are preferentially excluded from membrane surfaces. They decrease the activation energy for water transport during freezing and control the rate of cellular dehydration. Lyoprotectants are thought to stabilize membranes during drying by forming direct hydrogen bonding interactions with phospholipid head groups. In addition, lyoprotectants can form a glassy state at room temperature. Recently liposomes have been investigated to stabilize blood cells during freezing and freeze-drying. Liposomes modify the composition of cellular membranes by lipid and cholesterol transfer, which can stabilize or destabilize the low temperature response of cells.

Molecular study of the diffusional process of DMSO in double lipid bilayers

As a way to quantify the diffusion process of molecular compounds through biological membranes, we investigated in this study the dynamics of DMSO through an 1,2-Dipalmitoyl-sn-Glycero-3-Phosphocholine (DPPC) bilayer system. To properly account for the diffusion of DMSO due to a concentration gradient, a double DPPC bilayer was setup for our simulations. In such configuration, the aqueous phases can be explicitly associated with the extra and intracellular domains of the membrane, which is seldom the case in studies of single lipid bilayer due to the periodicity imposed by the simulations. DMSO molecules were initially contained in one of the aqueous phases (extracellular region) at a concentration of 5 wt.%. Molecular dynamics simulation was performed in this system for 95 ns at 350 K and 1 bar. The simulations showed that although many DMSO molecules penetrated the lipid bilayer, only about 10% of them crossed the bilayer to reach the other aqueous phase corresponding to the intracellular region of the membrane. The simulation time considered was insufficient to reach equilibrium of the DMSO concentration between the aqueous phases. However, the simulations provided sufficient information to estimate parameters to apply Fick's Law to model the diffusion process of the system. Using this model, we predicted that for the time considered in our simulation, the concentration of DMSO in the intracellular domain should have been about half of the actual value obtained. The model also predicted that equilibrium of the DMSO concentration in the system would be reached after about 2000 ns, approximately 20 times longer than the performed simulation.

Adoption of long-term cultures to evaluate the cryoprotective potential of trehalose for freezing hematopoietic stem cells

Dimethylsulfoxide (DMSO), which is widely used as a cryoprotectant for hematopoietic stem cells (HSC), has considerable toxicity for both the thawed cells and the patient. The aim of this study was to evaluate the cryoprotective potential of trehalose in comparison to DMSO for human HSC. Human bone marrow (BM) and peripheral blood stem cells (PBSC) of volunteer donors were cryopreserved in the presence of different concentrations of trehalose with and without insulin, as well as with DMSO 10%. After thawing to 37 degrees C colony-forming unit (CFU) assays were performed. Long-term marrow-cultures (LTMC) were established and used for the detection of long-term culture-initiating cells (LTCIC). The total amount of CFUs detected was 104+/-134 (mean+/-s.d.) in DMSO-preserved cells and 179+/-34 in trehalose-protected cells. For LTMC the best feeder layer proved to be fresh human BM and the most useful concentration of trehalose was 0.5 M. Using these culture conditions we could detect after 5 weeks LTMC a total of 172+/-28 CFUs for trehalose-protected cells and 170+/-52 for DMSO-preserved cells. In conclusion, trehalose exerts a similar cryoprotective potential for hematopoietic progenitor and stem cells like DMSO and could possibly replace DMSO at least in part as cryoprotectant in the setting of hematopoietic cell transplantation.

Comparison of various dimethylsulphoxide-containing solutions for cryopreservation of leucoreduced platelet concentrates

BACKGROUND AND OBJECTIVES

Leucoreduced platelet concentrates (LR-PCs) can be stored at 20-24 degrees C for 5-7 days. When LR-PCs are cryopreserved they can be stored for several years. For cryopreservation to become applicable in blood-bank practice, an off-the-shelf cryoprotectant is needed that can be added to the LR-PC in a sterile manner. For this, we varied the composition of the cryopreservation medium and studied various parameters of cryopreserved LR-PCs for up to 24 h after thawing at room temperature.

MATERIALS AND METHODS

LR-PCs in plasma or Composol were concentrated and divided into 2 units. To each unit, an equal part of 10% dimethylsulfoxide (DMSO) in plasma, Composol with or without 5% albumin, or GPO (pasteurized plasma-protein solution) was added. Freezing occurred at 1 degrees C/min and LR-PCs were placed in the vapour phase of nitrogen. LR-PCs were thawed at 37 degrees C and stored at room temperature. LR-PCs were tested for morphology, platelet recovery, swirling effect, and activation antigens at various time-points thereafter.

RESULTS

LR-PCs in 100%, 65% and 50% plasma supplemented with Composol showed good morphology scores (>250), limited CD62P expression (<35%), low CD63 expression (<20%) and a swirling effect of about 2, at 24 h after thawing. At the same time-point, platelet recovery was >80% under all conditions and CD42b expression varied between 70 and 85%. Results of LR-PCs in 15% plasma and Composol, with or without plasma substitutes, were not acceptable at 24 h after thawing, i.e. the morphology score was <200 and the CD62P expression was >40%.

CONCLUSIONS

A minimum of 50% plasma in the cryopreserved LR-PC is necessary to maintain an acceptable in vitro quality of platelets up to 24 h after thawing. Composol is a good candidate for using to prepare an off-the-shelf cryoprotectant.

Effects of cryopreservation on lymphocyte immunophenotype and function

Cryopreservation of isolated peripheral blood mononuclear cells (PBMCs) for phenotypic and functional analyses is considered a standard procedure in order to minimize operator-dependent inter-assay variability and to optimize the use of available resources. However, only few and somewhat conflicting data are presently available on the effects of cryopreservation on PBMCs, especially in samples from HIV-infected patients in which assessment of lymphocyte phenotype and function is of the outmost importance. In this study, we compared fresh versus frozen/thawed (F/T) samples isolated from 19 healthy individuals and 21 HIV-infected patients, showing that cryopreservation induces: (i) a profound decrease of CD62L expression, with a consequent significant decline of the calculated proportions of "naïve" (CD45RA+CD62L+) and "central memory" (CD45RO+CD62L+) T cells; (ii) an increase of the calculated proportions of "effector" CD8+ T cells (CD45RA+CD62L- and CD45RO+CD62L-) in the healthy subjects, while no changes were observed in the HIV-infected group; (iii) a significant decline of CC chemokine receptor 5 (CCR5) expression; (iv) a loss of proliferative responses to some HIV antigens (i.e. p24) and recall antigens [cytomegalovirus (CMV) and Influenza] in HIV-infected patients. We thus conclude that cryopreservation induces a consistent set of changes in PBMCs from both healthy and HIV-infected individuals, and that certain immunological studies of HIV-infected patients (i.e. studies of immune reconstitution following antiretroviral therapy in HIV-infected patients or studies of HIV-infectivity in vitro using CCR5-tropic strains) should be performed on fresh samples.

Multidisciplinary utilization of dimethyl sulfoxide: pharmacological, cellular, and molecular aspects

DMSO is an amphipathic molecule with a highly polar domain and two apolar methyl groups, making it soluble in both aqueous and organic media. It is one of the most common solvents for the in vivo administration of several water-insoluble substances. Despite being frequently used as a solvent in biological studies and as a vehicle for drug therapy, the side-effects of DMSO (undesirable for these purposes) are apparent from its utilization in the laboratory (both in vivo and in vitro) and in clinical settings. DMSO is a hydrogen-bound disrupter, cell-differentiating agent, hydroxyl radical scavenger, intercellular electrical uncoupler, intracellular low-density lipoprotein-derived cholesterol mobilizing agent, cryoprotectant, solubilizing agent used in sample preparation for electron microscopy, antidote to the extravasation of vesicant anticancer agents, and topical analgesic. Additionally, it is used in the treatment of brain edema, amyloidosis, interstitial cystitis, and schizophrenia. Several systemic side-effects from the use of DMSO have been reported, namely nausea, vomiting, diarrhea, hemolysis, rashes, renal failure, hypertension, bradycardia, heart block, pulmonary edema, cardiac arrest, and bronchospasm. Looking at the multitude of effects of DMSO brought to light by these studies, it is easily understood how many researchers working with DMSO (or studying one of its specific effects) might not be fully aware of the experiences of other groups who are working with it but in a different context.

Safety and efficacy of transfusions of autologous cryopreserved platelets derived from recombinant human thrombopoietin to support chemotherapy-associated severe thrombocytopenia: a randomised cross-over study

BACKGROUND

The increasing demand for platelet products, and concern over the transfusion-associated risks of alloimmunisation and infections, have motivated a search for improved methods aimed at keeping exposure to donor antigens to a minimum. Transfusion of thrombopoietin-derived autologous platelets might provide an alternative strategy. We aimed to compare the safety and efficacy of this strategy with that of transfusion with fresh allogeneic platelets in patients with severe chemotherapy-induced thrombocytopenia.

METHODS

20 patients with gynaecological malignancies were treated with two doses of 1.2 microg/kg recombinant human thrombopoietin. From day 12, we aimed to collect 50 units of platelets from these patients by plateletpheresis. Harvested platelets were cryopreserved in ThromboSol and 2% dimethyl sulfoxide (DMSO) for use in subsequent autologous transfusions. Patients then received carboplatin for up to six cycles. Patients were randomly assigned to group A (n=10), which received allogeneic fresh platelets at the first instance of severe thrombocytopenia (platelet count <15,000/microL) and then autologous cryopreserved platelets at the next, or to group B (n=10), which received first autologous and then allogeneic platelets. In subsequent cycles, all patients received autologous platelets while available. The primary endpoint was platelet count increment corrected for the number of platelets transfused and the patients' body-surface area. Analysis was by intention to treat.

FINDINGS

Treatment with recombinant human thrombopoietin significantly increased platelet count (median 2.3-fold [range 1.5-3.3], p<0.0001) in all but one patient in group A. The median number of platelets collected per patient was 53 units (14-66) in two collections (one to three). There was no significant difference in the corrected platelet count increments (CCIs) between the 19 paired transfusions of cryopreserved autologous platelets and fresh allogeneic platelets (median 1-h CCI 15.7 vs 19.8, p=0.398; median 24-h CCI 13.0 vs 18.1, p=0.398). 14 of the 19 patients had a good response (1-h CCI >7.5) to their first transfusion of allogeneic platelets. By contrast, all patients had a good response to their first transfusion of autologous platelets (p=0.063). Moreover, no significant decrease in the CCIs (p=0.405) was seen over six cycles after autologous platelet transfusions (n=63). No transfusion reactions or any serious adverse event was recorded during autologous platelet transfusions.

INTERPRETATION

Recombinant human thrombopoietin facilitated collection of multiple units of platelets, which could be cryopreserved and reinfused to counteract severe thrombocytopenia during multicycle chemotherapy. Transfusion of autologous cryopreserved platelets derived from recombinant human thrombopoietin can provide a viable strategy to minimise the risks of allogeneic platelet transfusions and provide a long-lasting supply of platelet support.

Biochemical, biophysical and haemorheological effects of dimethylsulphoxide on human erythrocyte calcium loading

The studies using dimethylsulphoxide (DMSO) and/or the 4-bromo-calcium ionophore A23187 (Br-A23187) often neglect the precise knowledge of some of their biochemical, biophysical and haemorheological effects. The aim of the present study was to evaluate these effects on erythrocytes after whole blood incubations with DMSO or Br-A23187 dissolved in DMSO. There were no significant differences between the different aliquots in the values of P(50), pH, erythrocyte deformability, erythrocyte membrane fluidity, haemoglobin and intracellular Ca(2+) concentrations ([Ca(2+)](i)). Aliquots with DMSO (independently of the presence of Br-A23187 or added Ca(2+)) had lower erythrocyte aggregation indexes and higher plasma concentrations of K(+)], Na(+)] and Ca(2+) than the aliquots without DMSO (independently of the presence of added Ca(2+)). Aliquots with added calcium (without the presence of Br-A23187 in DMSO) had a significantly higher erythrocyte acetylcholinesterase activity. Our data shows that calcium loading, the usual objective of Br-A23187 incubations, cannot be fulfilled with the studied experimental conditions. The coherence between our results and those obtained by other authors with different biological systems and different modulators of the rise on [Ca(2+)](i) suggests a non-specific effect of DMSO, disabling the action of the modulator. It can be reasoned that the decreased erythrocyte aggregation (without significant changes on the deformability or membrane fluidity) can result either from the decrease of the hydrogen bonding contribution to erythrocyte aggregation or the increased ionic strength influence on the erythrocyte membrane surface.

From anhydrobiosis to freeze-drying of eukaryotic cells

Using what has been learned from nature, it has become possible to stabilize biological structures, including intact cells, in the dry state. Stabilization of cells or tissues in the dried state is of considerable practical significance, as is described in this review. The need for stabilization of cells in the dried state is particularly urgent in bloodbanks, where proper storage of blood cells (platelets and erythrocytes) is still a major problem. Human blood platelets are stored in blood banks for 5 days, after which they are discarded according to Federal regulation. This short lifetime has led to a chronic shortage of platelets. We report here that platelets can be preserved by freeze-drying them with trehalose, a sugar found at high concentrations in organisms that naturally survive drying. We suggest that this finding will obviate the storage problem with platelets and that the principles established here may be extended to more complex eukaryotic cells.

Human platelets loaded with trehalose survive freeze-drying

Human blood platelets are stored in blood banks for 5 days, after which they are discarded, by federal regulation. This short lifetime has led to a chronic shortage of platelets, a problem that is particularly acute in immunosuppressed patients, such as those with AIDS. We report here that platelets can be preserved by freeze-drying them with trehalose, a sugar found at high concentrations in organisms that naturally survive drying. We suggest that these findings will obviate the storage problem with platelets. Trehalose is rapidly taken up by human platelets at 37 degrees C, with loading efficiencies of 50% or greater. Fluid-phase endocytosis plays an important role in this efficient uptake of trehalose, but other mechanisms may also be involved. Trehalose-loaded platelets were successfully freeze-dried, with excellent recovery of intact platelets. Rehydration from the vapor phase led to a survival rate of 85%. The response of these platelets to the agonists thrombin (1 U/ml), collagen (2 microg/ml), ADP (20 micromM), and ristocetin (1.6 mg/ml) was almost identical to that of fresh, control platelets. Analysis by Fourier transform infrared spectroscopy demonstrated that the membrane and protein components of trehalose-loaded platelets after freeze-drying, prehydration, and rehydration were remarkably similar to those of fresh platelets.

Correlation of in vivo and in vitro functions of fresh and stored human platelets

BACKGROUND

Long-term storage of human platelets has been hindered by the loss of function of the platelets stored under current protocols. Novel preservation methods have encouraged examination of platelet function of cells preserved by cooling and freezing. The function of the platelets was assessed by using both in vitro assays and an in vivo rabbit bleeding model.

STUDY DESIGN AND METHODS

Human platelets were stored in the presence or absence of 2 microM: cytochalasin B and 80 microM: EGTA/AM at 4 degrees C for 14 days or by freezing in the presence or absence of 5 percent DMSO. After the storage period, the platelets were resuspended in normal saline and infused into rabbits. Platelet function was assessed in vivo in a kidney bleeding model and in vitro by platelet-induced clot retraction and by platelet aggregation.

RESULTS

Platelets stored at either 4 degrees C or -145 degrees C exhibited shorter survival times in the rabbit circulation than did fresh platelets. Platelets cooled to 4 degrees C, in both the presence or absence of cytochalasin B and EGTA/AM treatment, or frozen in the absence of DMSO were not effective in halting bleeding. However, frozen DMSO-treated platelets were as effective as fresh platelets in stopping bleeding. In vitro assays showed that cooled platelets treated with cytochalasin B and egtazic acid/AM and frozen DMSO-treated platelets retained 30 to 40 percent platelet function, while the cooled and frozen control samples exhibited no platelet-induced clot retraction. With thrombin as the agonist, only frozen DMSO-treated platelets exhibited a tendency to aggregate, although at only 22 percent of the aggregation function of fresh platelets.

CONCLUSION

It is possible to freeze platelets and retain in vivo efficacy if the cryopreservative DMSO is included in the preparation. In vitro responses were greatly reduced by all of the storage protocols, but it may not be necessary to retain 100 percent in vitro function to have a platelet substitute or storage product that functions satisfactorily in vivo.

New plasma-reduced synthetic media, Fukushima cocktails, for the storage of platelets for transfusion

BACKGROUND

Donor plasma proteins are associated with non-hemolytic allergic reactions, such as urticaria or laryngeal edema, in platelet-transfusion recipients. Replacement of plasma with synthetic media from platelet concentrates (PCs) is considered to be effective in preventing such reactions. However, platelets preserved in media depleted of less than 10% plasma are reported to have functions inferior to those preserved in plasma.

METHODS

Fukushima Cocktails (FCs) contain glycerol (25, 50 or 100mM), sodium acetate, glucose and other components. To test the effect and determine the most suitable concentration of glycerol for platelet preservation, functions of platelets including aggregation, hypotonic shock response and swirling pattern and released biochemicals were measured with platelets preserved in Fukushima Cocktails. The effects of residual plasma on platelet functions were also evaluated. Autologous platelets stored for 3 days in solution containing 50 mM glycerol were transfused into healthy volunteer donors to evaluate their safety and survival.

RESULTS

The functions (aggregation and hypotonic shock response) of platelets preserved in Fukushima Cocktails with 10% residual plasma were preserved for 5-7 days as well as plasma controls, whereas platelets stored for 9 days in a medium lacking glycerol became swollen and beta-thromboglobulin and thromboxane B(2) increased. When the residual plasma was more than 5%, platelet functions including aggregation, hypotonic shock response and swirling pattern were well preserved for 7 days. The in vivo platelet survival rates at 24 and 48 h after transfusion of platelets stored for 3 days in Fukushima Cocktail were 77% and 60%, respectively, which were not less than autologous plasma-stored platelets.

CONCLUSION

Glycerol at a concentration of around 50 mM has a beneficial effect on platelet preservation for more than 7 days. The results of these experiments indicate that platelets stored in Fukushima Cocktail should be useful clinically.

Efficient translocation and processing with Xenopus egg extracts of proteins synthesized in rabbit reticulocyte lysate

Cell-free translation/translocation systems are broadly applied to examine gene expression and characterize the structure-function relationship of gene products. We present the characterization of Xenopus egg extract (XEE) translocation and processing of proteins synthesized in rabbit reticulocyte lysate. The XEE was prepared from eggs laid by adult female frogs that received serial injections of gonadotropins. The eggs were then dejellied in 2% L-cysteine-HCl and the cytoplasm extracted by centrifugation at 10,000 rpm for 15 min. The in vitro translocation and processing of XEE was examined with a cell-free translation system containing reticulocyte lysate, and appropriate messenger ribonucleic acid (RNA) or complementary deoxyribonucleic acid plasmids with RNA polymerase. Cell-free production of the following proteins were used to assess posttranslational modifications: Escherichia coli beta-lactamase for signal sequence cleavage, Saccharomyces cerevisiae alpha-mating factor for translocation and N-linked glycosylation, the soluble protein luciferase for functional activity, and the membrane-bound human insulin receptor for translation efficiency. All translation products were identified by [35S]-methionine labeling, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. The results demonstrate that (1) XEE produces near-complete signal sequence and N-glycosylation processing of proteins synthesized in reticulocyte lysate, (2) XEE contains endoplasmic reticulum-equivalent microsomes, which allows for protein translocation and protease protection, (3) the addition of XEE in the translation reaction does not affect synthesis and chemiluminescence activity of luciferase, (4) XEE is efficient in processing the nascent 160-kDa human insulin receptor precursor, a transmembrane protein, and (5) as compared to canine pancreatic microsomes, XEE translocation efficiency is minimally decreased with the addition of dimethylsulfoxide. These results are the first description of the combined use of XEE with reticulocyte lysate and clearly demonstrate a higher efficiency of translocation and processing compared to canine pancreatic microsomes. This method of cell-free translation and processing allows for more extensive in vitro examination of posttranslational modifications of secretory and membrane-bound proteins.

Platelets: preparations, transfusion, modifications, and substitutes

OBJECTIVE

To summarize current knowledge and recent progress pertaining to platelet concentrate preparations, modifications, and future prospects for platelet substitutes.

METHODS

Current publications identified through a search of an electronic literature database were evaluated and reviewed. Relevant data were abstracted into this article. Abstractions of the data were made depending on their relevance. This review starts with standard methods of platelet preparation and goes on to describe different modifications intended to optimize the product and increase its safety. The article concludes with a discussion of the use of hematopoietic growth factors and novel kinds of platelet components for future use.

CONCLUSIONS

Many modifications in the preparation of platelet transfusions have occurred in recent years. Platelets prepared by standard techniques contain significant numbers of donor leukocytes, which are responsible for several adverse effects. Awareness of this problem has lead to the development of effective means for their removal. Several methods to reduce the risk of viral and bacterial transmission through platelet transfusions are emerging. New technologies in the use of platelet substitutes have attempted to prolong the platelet storage potential and prevent the development of recipient alloimmunization. As the biological activities of growth factors become better understood, the clinical applications of novel recombinant products may redefine the concept of future platelet transfusions. It is important that research continues into the optimal methods for the preparation and use of platelet transfusions to provide maximal clinical benefits with minimal risk of complications.

Reduction of blood loss by infusion of human platelets in a rabbit kidney injury model

BACKGROUND

As a first step toward testing the efficacy of stored platelets or platelet substitutes in vivo, a kidney injury model was developed to assess the hemostatic properties of human platelets in normal and thrombocytopenic rabbits.

STUDY DESIGN AND METHODS

New Zealand white rabbits were made thrombocytopenic by two consecutive injections of busulfan. Two weeks later, human platelets were transfused to animals whose reticuloendothelial systems were inhibited by the administration of ethyl palmitate. The left kidney was exposed and a slice excised from the anterior pole. The blood was contained in a parafilm boat and absorbed by preweighed gauze to assess blood loss. The percentage of human platelets transfused to the rabbit was determined by flow cytometry on blood collected from the cut site using anti-CD42a (marker for human platelets). The degree of activation of the human platelets was determined using anti-CD62a (marker specific for human p-selectin).

RESULTS

Blood loss was similar in normal animals treated with saline alone (35.4 +/- 5.8 g; n = 4); ethyl palmitate and saline (42.5 +/- 5.7 g; n = 6, p = 0.4); or ethyl palmitate and fresh human platelets (45.7 +/- 7.9 g; n = 6, p = 0.3). Bleeding in thrombocytopenic rabbits infused with saline was increased (75.6 +/- 3.9 g; n = 7) as compared with nonthrombocytopenic animals. A significant reduction in blood loss was noted in thrombocytopenic rabbits given fresh human platelets (51.6 +/- 4.5 g; n = 6, p = 0.0023). Transfusion of human platelets to rabbits did not cause activation of the platelets. Furthermore, transfusion of thrombin-activated platelets (60-98% activated) to thrombocytopenic rabbits reduced blood loss (54 +/- 7.3 g; n = 7) to the same extent as fresh platelets.

CONCLUSIONS

This is the first report describing a kidney injury model developed to assess the efficacy of fresh and activated human platelets in reducing blood loss in thrombocytopenic rabbits. This model could monitor the efficacy of human platelets prepared by various preservation protocols in suppressing bleeding in rabbits.

Platelet cryopreservation using a reduced dimethyl sulfoxide concentration and second-messenger effectors as cryopreserving solution

Cryopreservation of platelets is of great interest since it could extend to years the shelf life of therapeutic platelet concentrates (PCs) and facilitate stockpiling and inventory control in blood banking. We have compared the cryopreservation of PCs by the standard method using 6% Me(2)SO as cryoprotectant with the method of freezing employing low concentrations of Me(2)SO (2%) plus ThromboSol, a mixture of second-messenger effectors that protect platelets from cold damage. PC pools were treated either with 6% Me(2)SO or with ThromboSol and 2% Me(2)SO and then placed directly in a -80 degrees C freezer or in the vapor phase of a liquid nitrogen freezer (-120 degrees C). After storage for 1 week or for 3 months, samples were removed, thawed, and analyzed. Measurements included cell recovery, biochemical parameters, membrane glycoproteins (GPs), platelet aggregation, and binding of radiolabeled von Willebrand factor (vWF) and fibrinogen. PCs cryopreserved with ThromboSol and 2% Me(2)SO displayed a platelet recovery (90%) equivalent to those frozen with 6% Me(2)SO. Following either cryopreservation procedure, platelets showed increased surface expression of P-selectin and moderate loss of GP Ibalpha in comparison to fresh platelets. The aggregatory response to ristocetin and the binding of vWF were similar in platelets frozen by either procedure. Finally, both methods promoted comparable impairment of the reactivity of platelets to thrombin, aggregation and binding of fibrinogen and vWF, compared to that of fresh platelets. In summary, cryopreservation of PCs using reduced Me(2)SO concentration and ThromboSol yields platelets with in vitro functional characteristics equivalent to those of cells frozen with the conventional method using 6% Me(2)SO.

Enhanced circulatory parameters of human platelets cryopreserved with second-messenger effectors: an in vivo study of 16 volunteer platelet donors

Platelet transfusion represents an important component of the therapy for thrombocytopenic patients. Prolonged storage capabilities for platelets would alleviate many problems associated with blood banking. Unfortunately, current cryopreservation methods are complex to implement and result in loss of cell number and functional activity. Previous in vitro studies have shown that the use of ThromboSolTM, a platelet-stabilizing formulation, in the cryopreservation of platelets results in significant retention of cell number and in vitro functional activities in addition to reducing the DMSO requirement to only 2%. We evaluated the in vivo circulatory parameters of platelets cryopreserved with ThromboSol. Single donor platelet units were obtained from healthy volunteers (n = 16); the units were then split and cryopreserved with either ThromboSol and 2% DMSO or 6% DMSO alone. Following storage at -80 degrees C for 7-10 d the samples were thawed, washed and radiolabelled with either 51Cr or 111In. The paired samples were then mixed and reinfused into the autologous volunteer. At various time intervals following transfusion a blood sample was drawn and the quantity of circulating labelled platelets was determined. The percent recovery and survival time was determined by multiple-hit analysis. The ThromboSol-treated platelets, as compared to the 6% DMSO-treated platelets, displayed statistically higher percent recovery (40.2% v 28.8%) and survival time (166.3 h v 152.1 h). These results demonstrated that platelets cryopreserved with ThromboSol displayed superior in vitro and in vivo characteristics as compared to the standard 6% DMSO method. The use of ThromboSol allowed for a 3-fold reduction in the DMSO concentration in conjunction with a 40% increase in circulating cell number and normal survival times.

Determination of human platelet membrane permeability coefficients using the Kedem-Katchalsky formalism: estimates from two- vs three-parameter fits

Attempts to cryopreserve human blood platelets have resulted in poor postthaw survival rates and have been inadequate for routine clinical application. As a result, most blood banks maintain platelets in nonfrozen solutions. Using this approach, platelets can be stored for only about 5 days and are then discarded. This situation greatly limits the use of platelet transfusion in clinical practice. Information regarding fundamental cryobiological characteristics can be applied to predict platelet response to cryoprotective agent (CPA) addition/removal and to cooling/warming. Methods can then be engineered to optimize cryopreservation procedures, thereby minimizing platelet damage and maximizing postthaw recovery. It was therefore the purpose of this study to determine some of the necessary biophysical parameters required for this process: (i) plasma membrane hydraulic conductivity (Lp), (ii) cryoprotectant solute permeability coefficient (Ps), (iii) the associated reflection coefficient (sigma), and (iv) their activation energies. The CPAs studied included dimethyl sulfoxide (Me2SO) and propylene glycol at 1.5 M concentration. Permeability was measured at 22, 10, and 4 degrees C using a modified Coulter counter in conjunction with a water-jacketed beaker system for temperature regulation. The Kedem-Katchalsky formalism was used to estimate the parameters using: (1) a three-parameter fit and (2) a two-parameter fit in which a noninteracting value of sigma was calculated. Two-parameter estimates were in closer agreement with previously published values, and these were used in a model to simulate addition and removal of 0.64 M (5%) and 1.0 M (7.8%) Me2SO, the most common CPA currently used in empirically determined platelet cryopreservation protocols.

Enhanced retention of in vitro functional activity of platelets from recombinant human thrombopoietin-treated patients following long-term cryopreservation with a platelet-preserving solution (ThromboSol) and 2% DMSO

Chemotherapy-induced thrombocytopenia represents a significant clinical problem in the management of patients with malignancy. Recombinant human thrombopoietin (rhTPO) is a potent stimulator of platelet production in vivo. The ability to cryopreserve rhTPO-derived platelets would enable the use of autologous platelets during the period of thrombocytopenia. ThromboSol is a platelet-stabilizing formulation consisting of second messenger effectors that inhibit specific activation pathways endogenous to platelets. To investigate the effect of ThromboSol cryopreservation, platelets from rhTPO-treated patients (n = 23) and normal donors were treated with ThromboSol and 2% DMSO and cryopreserved for up to 6 months. The platelets were thawed at different intervals and tested for retention of platelet functional activity in vitro. Following a short-term storage (1 week), the cryopreserved platelets from patients treated with rhTPO exhibited significantly higher retention of functional activities including discoid morphology (70% v 57%), extent of shape change (19% v 13%) stirring shape change (15% v 11%) and hypotonic shock response (56% v 25%), as compared to the cryopreserved platelets from controls. Furthermore, there was no further significant loss of functional activity following cryopreservation for up to 6 months. These findings suggest that cryopreservation of platelets from rhTPO-treated donors may provide a useful novel strategy for autologous or allogeneic donation for subsequent transfusions to manage treatment-related thrombocytopenia.