Human platelets labeled at two discrete biotin densities are functional in vitro and are detected in vivo in the mouse circulation. A promising approach to monitor in vivo platelet survival in clinical research

Objective The production of platelet concentrates (PCs) is evolving and their survival capacity needs in vivo evaluation. This requires that the transfused platelets (PLTs) be distinguished from those of the recipient. Labeling at various biotin (Bio) densities allows one to concurrently trace multiple PLT populations, as reported for red blood cells. A method is described to label human PLTs at two discrete densities of biotin for future clinical trials.

Material and Methods Injectable-grade PLTs were prepared in a sterile environment, using injectable-grade buffers and GMP-grade Sulfo-NHS-Biotin. Sulfo-NHS-Biotin concentrations were chosen to maintain PLT integrity and morphology, to avoid potential alloimmunization while enabling the detection of circulating BioPLTs in a severe immuno-deficient mouse model, using ex vivo flow cytometry. The impact of biotinylation on human PLT survival was evaluated in vivo in the mouse.

Results BioPLTs labeled with 1.2 or 10 microg/mL Sulfo-NHS-Biotin, displayed normal ultrastructure, retained aggregation and secretion capacity and normal expression of the main glycoproteins. The procedure avoided detrimental PLT activation or apotosis signals. Transfused human BioPLT populations in the mouse circulation could be distinguished from one another and from unlabeled circulating mouse PLTs and their survival was comparable to that of unlabeled human PLTs.

Conclusion Provided low Sulfo-NHS-Biotin concentrations (≤10 microg/mL) are used, injectable-grade BioPLTs are compliant with safety regulations, conserve PLT integrity and permit accurate in vivo detection. This alternative to radioisotopes, which allows one to follow different platelet populations in the same volunteer should be valuable to assess new PC preparations and to monitor platelet survival in clinical research.

Publication History

Article published online:
18 June 2021