Background: Measuring survival of human platelets following their circulation in the blood allows for investigations of function, clearance, and the impact of their treatment prior to infusion. The Nonobese diabetic/severe combined immunodeficiency (NOD-SCID) mouse is an ideal animal model given its compatibility with xeno-transfusion. Herein, we use carboxyfluorescein diacetate succinimidyl ester (CFDA-SE) to fluorescently label apheresis platelets, cold-stored platelets (CSP), 6% Dimethylsulfoxide cryopreserved platelets (CPP), and Thrombosomes®, a human platelet derived lyophilized hemostatic (LHP), to measure their circulation persistence in NOD–SCID mice.

Aims: Assess the circulation persistence of apheresis platelets, cold-stored platelets, cryopreserved platelets, and Thrombosomes®.

Methods: Human apheresis platelets were incubated with 50µM CFDA-SE at room temperature for 60 minutes. Labeled platelets were used as a test article or further processed into CSP (stored at 4°C unagitated), CPP (stored at -80°C), or LHP (stored at room temperature). NOD-SCID mice (n=6 per group) were infused by tail vein injection and whole blood samples were taken by submandibular venipuncture. The study infusion dates were staggered to accommodate processing of each product. Apheresis platelets were infused 48 hours post-collection, CSP and CPP were infused 8 days after collection, and LHP were infused 9 days after platelet collection. Labeled platelet counts were measured by flow cytometry.

Results: Apheresis platelets had the highest initial recovery (2 minutes post infusion) at 69%, followed by CSP at 38%, CPP at 21%, and finally LHP at 9% (Figure 1). These differences in platelet recovery persisted throughout the other timepoints.

Conclusion(s): The NOD-SCID mouse model of platelet circulation persistence successfully differentiated between four platelet products. It demonstrated that LHP are cleared more rapidly than liquid stored platelets and that CSP and CPP are intermediate in clearance. These differences in circulation persistence are seemingly correlated to platelet activation and cell damage induced by the different platelet treatment conditions.

Figure 1

Percent recovery for fluorescent platelets in blood samples collected from mice infused with each platelet product. Percent recovery is calculated as the measured flow cytometry count divided by the theoretical count given the known platelet product concentrations, infusion volume, and mouse blood volume. Each point is the average value for that time point and error bars are standard deviation. The study infusion dates were staggered to accommodate the manufacture of each product. The apheresis platelets were infused on day 3 -48 hours post-collection-. The cold-stored platelets and cryopreserved platelets were infused 8 days after collection. The Thrombosomes® were infused 9 days after platelet collection.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/assessing-circulation-persistence-of-human-platelet-products-in-a-nod-scid-mouse-model/