Platelet subpopulations and contribution to hemostasis

Platelets are traditionally considered a homogeneous population of anucleate cells derived from megakaryocytes, primarily responsible for hemostasis and thrombus formation. However, advances in platelet phenotyping and functional assays have revealed substantial heterogeneity within the platelet population, identifying distinct subpopulations with specialized functions. These subpopulations, including reticulated, procoagulant, aggregatory, and coated platelets, are characterized by distinct molecular signatures, activation thresholds, and functional roles that differentially influence thrombin generation, clot stability, and vascular integrity. Their variable reactivity and interactions with leukocytes and coagulation pathways position them as critical mediators of thromboinflammation. These subpopulations also display varied responses to commonly used antiplatelet medications. Reticulated platelets (RPs), for instance, are younger and more reactive, and have been associated with relative resistance to aspirin and P2Y12 inhibitors. Despite significant advances, the precise contributions of platelet subpopulations to hemostasis and disease progression remain poorly understood, largely due to the lack of standardized markers and methodological variability across studies. This review critically summarizes current insights into platelet heterogeneity, emphasizing the functional relevance of specific subpopulations and their pharmacologic profiles while addressing existing limitations and unresolved controversies. Furthermore, it discusses emerging research strategies aimed at refining platelet classification and explores how a deeper understanding of platelet heterogeneity may facilitate the development of precision-based diagnostic tools and targeted antiplatelet therapies. Such approaches may ultimately improve risk stratification and therapeutic outcomes in thrombotic and inflammatory disease.