Platelet heterogeneity in ageing and cancer: A single-cell atlas reveals transcriptional state-specific associations with metastasis.

Platelets have been increasingly recognized as versatile regulators of ageing, immunity, and cancer, yet their functional heterogeneity has remained poorly defined. We performed the first large-scale single-cell RNA sequencing of 28,192 platelets from healthy, aged, metastatic, and treated mice using the BD Rhapsody platform. Our analysis revealed four conserved and functionally distinct platelet transcriptional states: haemostatic platelet (HP), neural gene-enriched platelet (NEP), platelet-leukocyte aggregate (PLA) and platelet-erythrocyte aggregate (PEA). Among these states, Tpm2-high HP is linked to ageing-associated lung metastasis and is characterized by cytoskeletal remodelling gene signatures. The PLA state was predicted to be a signalling hub for immunothrombosis, with a PLA-Bridge subpopulation coordinating immune-adherent platelets via the Ppbp-Cxcr2 and Thbs1-Cd47 checkpoint axes. Strikingly, AAV-mPf4 gene therapy was associated with a NEP-associated transcriptional program, which mitigates age-related functional decline. This study provides a single-cell transcriptomic atlas of murine platelets under ageing and metastasis conditions and reveals transcriptional state-specific heterogeneity. This study also proposes PF4-based interventions and cytoskeletal candidates for diagnosis and therapy.