Background: Mechanical circulatory support (MCS) is vital for patients with advanced heart failure. Yet, long-term MCS is associated with bleeding coagulopathy, felt to be driven by more than anticoagulant excess. Due to undefined etiology, device-related bleeding lacks efficient therapeutic management. We showed that MCS-generated hypershear causes platelet dysfunction via downregulation of adhesion receptors, impairing aggregation, promoting pro-apoptosis, and microvesiculation – all contributors to bleeding. As recently recognized, glycosylation of platelet surface receptors, i.e. platelet “sugar coat,” plays a major role in regulation of platelet function and lifespan.

Aims: We tested the hypothesis that hypershear stress promotes platelet desialylation thus facilitating microvesiculation and platelet count reduction.

Methods: Gel-filtered human platelets were exposed to neuraminidase-1, continuous hypershear (70 dynes/cm²,10’), or both; optionally platelets were pre-treated with oseltamivir (neuraminidase inhibitor) prior to shear exposure. Platelets were co-stained with fluorophore-conjugated anti-CD42a, SNA and MAL lectins binding 2,6- and 2,3-linked sialic acids; flow cytometry was performed to quantify platelet surface sialylation, platelets, and microparticles. Fluorescent nanobeads SPHERO^TM were used as a size standard.

Results: Platelet exposure to hypershear stress and sialidase induced platelet surface desialylation as indicated by significant decrease of SNA and MAL lectins’ binding (Fig.1A-B); MAL binding indicating 2,3-linked sialic acids was mainly affected by both shear stress and neuraminidase-1. Platelet desialylation induced by shear stress and neuraminidase was associated with a substantial decrease in platelet count and increase in microparticles (Fig.1C-D). Neuraminidase reinforced shear-mediated microvesiculation, but not platelet count drop. Oseltamivir slightly inhibited shear-mediated desialylation, preserved platelet count (30% increase), and decreased microparticle generation (29% decrease) (Fig.1A-D).
Exposure to hypershear stress and neuraminidase-1 (0.1 mU/mL) promotes platelet desialylation. Platelet desialylation is associated with the decrease of platelet count and intensification of platelet microvesiculation. Neuraminidase inhibition by oseltamivir partially preserves platelet sialylation, prevents platelet count drop, and decreases microvesiculation mediated by hypershear. A, B – platelet surface sialylation as indicated by SNA and MAL lectins, binding to 2,6- and 2,3-linked sialic acid moieties respectively; C, D – the number of platelets and platelet-derived microparticles. N = 6, Mean ± SEM, one-way ANOVA followed by Sidak’s multiple comparisons test: **, ## – p < 0.01 as compared with non-sheared and sheared control, respectively.

Conclusions: Shear stress induces platelet surface desialylation with associated microvesiculation and reduction in platelet count. Neuraminidase inhibition restores platelet count and decreases microparticle generation caused by hypershear. Developing therapeutic strategies for preservation of platelet sialylation offers significant translational potential for pharmacologic management of MCS-related platelet dysfunction, coagulopathy, and bleeding complications.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/stripping-a-platelet-sugar-coat-by-shear-shear-mediated-platelet-desialylation-promotes-reduction-in-platelet-count-and-increased-microvesiculation/