In vivo recovery of human platelets in severe combined immunodeficient mice as a measure of platelet damage
ABSTRACT Clinical performance of human platelet (PLT) products processed or stored under novel conditions is difficult to predict based on in vitro studies alone. Recovery and survival of radiolabeled PLTs in human subjects are used as surrogate markers for PLT efficacy in development of new products. Such experiments pose some risk to the participants, can be a financial burden on the sponsor, and may stifle innovation and development of new PLT products. Animal models for in vivo recovery and survival of human PLTs are limited by rapid, immune-mediated clearance of human cells. The severe combined immunodeficient (SCID) mice allowed prolonged circulation of human PLTs and were used to detect differences in recovery and survival between chemically damaged, aged PLTs, or normal PLTs.
Human PLTs were transfused into SCID and wild-type (WT) mice, and the recoveries and survival times were detected in mouse whole blood by flow cytometry with an anti-human CD41-fluorescein isothiocyanate monoclonal antibody. Recoveries of damaged PLTs were compared to normal PLTs.
Recoveries were significantly shorter in WT than in SCID mice at 4 hours after transfusion (WT, 20.8 +/- 5.4%, n = 12; SCID, 63.8 +/- 8.4%, n = 10) and with a t((1/2)) estimate of 2 hours for WT and 7 hours for SCID mice. Human PLTs damaged either by chemical treatment or by improper storage exhibited decreased recoveries in SCID mice.
The SCID mouse model can detect differences between damaged and control human PLTs and could be useful in evaluating novel PLT collection, processing, and storage technologies that may impact PLT quality.
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ABSTRACT: Bacterial sepsis is still a complication in patients transfused with stored platelets (PLTs). We have recently demonstrated that selected antimicrobial peptides (AMPs) have bactericidal activity in bacteria-spiked PLTs. In a subsequent preclinical study, we have also shown that these AMPs do not elicit antibody response in rabbits and treatment of PLTs before transfusion does not affect their in vivo recovery and survival in severe combined immunodeficient mice. Here we have selected two such AMPs, Arg-Trp (RW) repeats of tri- and tetra-peptides (RW3 and RW4) in combination (i.e., cocktail), and evaluated their effect on the in vitro properties of PLTs. Leukoreduced ABO- and D-identical whole blood-derived PLT concentrates were pooled and divided into two 60-mL aliquots in CLX storage bags. On Day 0, one bag received a peptide cocktail of RW3 plus RW4 at 0.01 mmol/L final concentration (test) and the other bag received only phosphate-buffered saline (PBS), the AMP solvent (control). The treated PLTs were stored for 7 days at 20 to 24°C. Samples were collected on Days 1, 5, and 7 to evaluate the in vitro properties of PLTs with standard assays. In vitro properties of the RW3 plus RW4 cocktail-treated PLTs were similar to those incubated with PBS only. There were no significant differences between the control and test PLTs during the 7-day storage. Leukoreduced whole blood-derived PLTs treated with a mixture of RW3 and RW4 peptides maintain their in vitro properties during 7 days of storage.Transfusion 01/2014; 54(6). DOI:10.1111/trf.12534 · 3.57 Impact Factor
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ABSTRACT: Bacterial sepsis is a complication attributed to room temperature (RT)-stored platelets (PLTs) in transfusion medicine. Antimicrobial peptides (AMPs) are emerging as new therapeutic agents against microbes. We had previously demonstrated bactericidal activity of select synthetic AMPs against six types of bacteria in stored PLTs. In this report, we tested these AMPs for their potential antibody response and interference with the recovery and survival of human PLTs in an animal model. Two separate studies were conducted to evaluate the safety of the synthetic AMPs. 1) Two AMPs (PD3 and PD4), derived from thrombin-induced human PLT microbicidal protein, and four repeats of arginine-tryptophan (RW), containing two to five repeats (RW2-RW5), were tested in rabbits for potential antibody response. 2) RT-stored human PLTs treated for 2 hours with each of the six AMPs individually or with phosphate-buffered saline (PBS) alone were infused into severe combined immunodeficient (SCID) mice to evaluate their in vivo recovery and survival by flow cytometry. Except for PD3, which showed a weak immune response, all other peptides did not induce any detectable antibodies in rabbits. Furthermore, all six AMPs tested did not significantly affect the in vivo recovery and survival of human PLTs in SCID mice compared to PBS alone-treated PLTs. Preclinical evaluation studies reported here demonstrate that the selected AMPs used in the study did not adversely affect the human PLT recovery and survival in the SCID mouse model, suggesting further study of AMPs toward addressing the bacterial contamination of PLTs.Transfusion 06/2013; 54(3). DOI:10.1111/trf.12318 · 3.57 Impact Factor
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ABSTRACT: BACKGROUND: Platelet (PLT) storage at room temperature (RT) is limited to 5 days to prevent growth of bacteria, if present, to high levels. Storage in cold temperatures would reduce bacterial proliferation, but cold‐exposed PLTs are rapidly cleared from circulation by the hepatic Ashwell‐Morell (AM) receptor, which recognizes PLT surface carbohydrates terminated by β‐galactose. We cycled storage temperature between 4 and 37°C to preserve PLT function and reduce bacterial growth.STUDY DESIGN AND METHODS: Temperature‐cycled (TC) human PLTs were stored at 4°C for 12 hours and then incubated at 37°C for 30 minutes before returning back to cold storage. PLTs stored at RT or at 4°C (COLD) or TC for 2, 5, and 7 days were infused into SCID mice and the in vivo recovery was determined at 5, 20, and 60 minutes after transfusion.RESULTS: PLTs stored for 2 days in COLD had significantly lower in vivo recoveries than RT PLTs. TC PLTs had improved recoveries over COLD and comparable to RT PLTs. After 5‐ and 7‐day storage, TC PLTs had better recoveries than RT and COLD PLTs. PLT surface β‐galactose was increased significantly for both COLD and TC PLTs compared to RT. Blocking of the AM receptor by asialofetuin increased COLD but not TC PLT recovery.CONCLUSION: TC cold storage may be an effective method to store PLTs without loss of in vivo recovery. The increased β‐galactose exposure in TC PLTs suggests that mechanisms in addition to AM receptors may mediate clearance of cold‐stored PLTs.Transfusion 06/2013; 53(6). DOI:10.1111/j.1537-2995.2012.03896.x · 3.57 Impact Factor