Background: Platelet transfusions are an essential treatment for attenuating bleeding but are often ineffective in cases of intractable hemorrhage. Although anucleate, mature platelets synthesize protein de novo, making them amenable to mRNA gene therapy; however, there remains to be an effective transfection technique. Advancements in lipid nanoparticle technology has enabled leading COVID vaccines and is an efficient method to deliver nucleic acids into target cells. Recently, we developed a LNP approach to successfully express exogenous protein in platelets [unpublished data], a first step towards demonstrating that donor platelet coagulability can be engineered. However, the effects of LNP treatment on platelet function has yet to be investigated.

Aims: To determine whether LNP-treated donor platelets are functionally similar, or better, in vitro, than platelets currently transfused clinically as a next step to establish LNP engineered platelets as a new cell therapy.

Methods: The hemostatic profiles of LNP-treated and clinical donor platelets were assessed using an adapted rotational thromboelastometry model of dilutional coagulopathy. LNP-treated platelets were also stimulated with conventional platelet agonists to test if responsiveness is similar, or better than clinical platelets using flow cytometry.

Results: LNP-treated platelets have a comparable hemostatic profile to clinically transfused platelets and significantly improved clotting dynamics when spiked into hemodiluted whole blood in an in vitro transfusion simulation. LNP-treated platelets also respond comparably, and in some cases more potently to agonist simulation compared to untreated platelets as indicated by similar p-selectin surface presentation.

Conclusion(s): LNPs are an effective way to deliver exogenous nucleic acids into platelets; they do not significantly change platelet coagulability or responsiveness to agonists. LNP platelet engineering is a promising new approach to load platelets with procoagulant protein to enhance their function.

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Figure 1. LNP-treated platelets have -A- similar clot firmness and -B- clot formation time compared to untreated transfusable platelets in a rotational thromboelastometry model of dilutional coagulopathy. Error bars represent standard deviation. ****P < 0.00001

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Figure 2. LNP-treated platelets are more responsive to thrombin stimulation than untreated donor platelets. Error bars represent standard deviation. **P < 0.001; ***P < 0.0001

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/platelets-genetically-modified-with-mrna-lipid-nanoparticles-are-functionally-similar-to-clinically-transfused-platelets-in-vitro/