Driehaus, E. R. | bioRxiv Science

bioRxiv2025

VAMP8 Deficiency Attenuates AngII-Induced Abdominal Aortic Aneurysm Formation via Platelet Reprogramming and Enhanced Extracellular Matrix Stability

BACKGROUNDAs vascular sentries, platelets, and their ability to release a host of bioactive molecules, are critical for vascular homeostasis as well as hemostasis. Despite data linking platelet activation to abdominal aortic aneurysms (AAA) and rupture, the underlying mechanisms remain poorly understood. This study addresses the hypothesis that VAMP8, the primary v-SNARE controlling platelet exocytosis, contributes to AAA formation. METHODS AND RESULTSIn an AngII-infused hypercholesterolemic mouse model, we observed significant platelet consumption, indicated by decreased platelet counts at both acute (5-day) and chronic (28-day) time points. Platelets accumulated at sites of elastin degradation and within false lumens of the abdominal aorta after 28 days of AngII infusion. Bulk RNA sequencing analysis of washed platelets and their releasates after 5 days of AngII infusion revealed significant transcriptomic changes, suggesting rapid reprogramming of platelet function. Parallel RNA-seq analysis of suprarenal aortic tissue highlighted changes in genes associated with extracellular matrix (ECM) organization, inflammation, and platelet signaling, linking platelets to vascular remodeling suggesting a "platelet-aorta axis". Laser speckle imaging in a FeCl injury model confirmed that VAMP8 deficiency impaired platelet function, resulting in delayed thrombosis. In vivo experiments demonstrated that VAMP8-/- mice were protected against AngII-induced AAA and aortic rupture. Aortic diameter analysis further revealed that VAMP8 deficiency significantly attenuated AngII-driven aortic pathology. RNA-seq analysis of platelets and aortic tissue suggests that loss of VAMP8 affects expression of genes controlling ECM degradation and aortic wall stability consistent with the protective effect of VAMP8 loss on AAA. CONCLUSIONShort-term AngII infusion appears to reprogram the platelet transcriptome, which may affect the aorta and contribute to AAA formation. Controlling cargo release from platelets via VAMP8 deficiency results in profound attenuation of aortic aneurysms. This introduces a novel paradigm for understanding the impact of reprogrammed platelet cargo secretion and function in aortopathies. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC="FIGDIR/small/635525v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@22bcecorg.highwire.dtl.DTLVardef@a15207org.highwire.dtl.DTLVardef@1106fd8org.highwire.dtl.DTLVardef@1ee0ea_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIPlatelet transcriptome is altered at early aneurysmal stage. C_LIO_LIVAMP8 deficiency attenuates aortic aneurysms, potentially via enhanced ECM stability. C_LIO_LIVAMP8 deficiency significantly alters various genes contributing to aortic wall structure and stability in both platelets and suprarenal aortic tissue. C_LI

physiology↗

bioRxiv2024

Single-Platelet Mapping of Jugular, Puncture-Wound Thrombi Reveals the Spatial Evolution of Platelet Activation

BackgroundThe contributions of platelet activation to thrombus formation during hemostatic bleeding cessation likely involve multiple activation states. However, the spatial and temporal distribution of platelets in these states has not been defined in a clot. ObjectivesTo use single-platelet mapping of activation states within jugular vein puncture thrombi to determine how the spatial distribution of platelet state evolves during hemostasis. MethodsMontaged, wide-area electron micrographs (EM) were taken at various time points, post-puncture, and annotated for platelet activation state. These classifications were mapped onto the images to identify regions of platelet activation and calculate neighbor associations. The importance of -granule secretion was tested using VAMP8-/- mice. Resultsmapping of platelet activation states at 1 min post-puncture showed extensive spatial intermixing of most platelet activation classes. No high-activation-state, platelet-rich core was observed in 5-min post-puncture thrombi, rather such platelets tended to be localized on the interior surfaces of thrombus vaults open to the circulation. Only at a later stage, 20 min post-puncture, was distinct clustering of high activation, degranulated, cytosol-rich platelets observed. These clusters localized to the central portion of the intravascular platelet-rich crown, and they were now inaccessible to the circulation. Counterintuitively, deletion of the primary platelet v-SNARE, VAMP8, increased the frequency and spatial clustering of highly activated, degranulated platelets in association with intra-thrombus vault surfaces at 5 min post puncture. ConclusionsWe conclude recent multi-activation state models can provide a realistic thrombus formation framework if linked together to encompass the dynamics of puncture wound formation.

systems biology↗