Platelet-Hitchhiking Lipid Nanoparticles Provide Selective Vascularization After Myocardial Infarction

Introduction: Acute myocardial infarction (AMI) remains a major global health challenge and a leading cause of mortality due to thrombosis triggered by endothelial damage under hypoxic conditions. Traditional pro-angiogenic therapies, mainly targeting vascular endothelial growth factor (VEGF), have struggled with issues of targeted delivery and complications from abnormal vessel formation. To address these challenges, we introduce a novel conformation-sensitive platelet-hitchhiking lipid nanoparticle (CSPH-LNP). This innovative delivery system co-delivers VEGF mRNA and PDGFRβ siRNA directly to ischemic heart tissue, ensuring precise localization and enhanced endothelial cell proliferation (Fig. 1c). The CSPH-LNP approach not only improves angiogenesis but also promotes significant functional recovery of the ischemic myocardium, offering a promising new avenue for AMI treatment.

Materials and

Methods: Lipidoids were first synthesized via a one-pot, two-step, three-component reaction and formulated into LNPs. These LNPs, encapsulating luciferase mRNA, were screened in mouse cardiac endothelial cells for mRNA expression, cell viability, and potential platelet activation using high-throughput techniques under cardiac conditioned medium. Flow cytometry assessed the binding efficiency of CSPH-LNP to resting and activated platelets. Bioluminescence and fluorescence imaging characterized the biodistribution and expression of CSPH-LNPs. Immunofluorescence staining for CD31 and Troponin T evaluated vascularization and myocardial recovery in mouse myocardium sections. Echocardiograms at 14- and 28-days post-administration assessed functional cardiac recovery.

Results, Conclusions, and Discussions: Using a novel tandem and in situ synthesis method, we developed 102 lipidoids with tertiary amine and ester groups. The optimal lipidoid outperformed the DLin-MC3-DMA formulation in luciferase mRNA expression, preserving over 85% cell viability in mouse cardiac-derived endothelial cells without significant human platelet activation (Fig 1a). The leading lipidoid was developed to co-deliver VEGF-A mRNA and PDGFRβ siRNA to form the lipid nanoparticles. This lipidoid was engineered to co-deliver VEGF-A mRNA and PDGFRβ siRNA to form a lipid nanoparticle (Fig. 1b). Upon injection, CSPH-LNPs specifically targeted resting platelets via a CD61 antibody linkage, and released their cargo in myocardial infarction zones through thrombin-mediated cleavage of a thrombin-cleavable peptide (Fig 1c). Flow cytometry verified effective CSPH-LNP binding to platelets, released by either ADP or thrombin stimuli (Fig 1d). In vivo imaging confirmed preferential localization and expression of CSPH-LNPs in the heart, with minimal off-target effects (Fig 1e). Immunofluorescent staining demonstrated that CSPH-LNP treatment notably enhanced vascularization and myocardial recovery (Fig 1f). Echocardiographic assessments indicated significant improvements in left ventricular ejection fraction and systolic volume post-treatment (Fig 1g), highlighting the CSPH-LNP's effectiveness in promoting vascularization and functional myocardial recovery after infarction.

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