TNFα drives platelet hyperreactivity and thromboinflammation through regulation of hematopoietic stem and progenitor...

TNFα is the primary age-related cytokine responsible for hyperreactive platelet formation. In mouse models, increased TNFα induced abnormal megakaryocyte development and platelet activity. Here, we extend these findings to demonstrate that TNFα drives this thrombotic phenotype through expansion of the hematopoietic stem and progenitor cell (HSPCs) compartment. Using HSPC-specific TNFα receptor labeling and single cell RNA sequencing, we found that TNFα receptors are absent from megakaryocytes and their progenitors (MkPs) indicating that TNFα does not directly act on these cells. Chronic TNFα exposure expanded HSPCs in the bone marrow and extramedullary tissues - and these expanded HSPCs retained functional repopulation capacity. Using species-specificity TNFα receptor activation, we further demonstrate that TNFαR1 signaling is sufficient to induce platelet hyperreactivity independent of HSPC expansion. Unlike emergency hematopoiesis, chronic TNFα promoted megakaryopoiesis through the canonical hematopoietic hierarchy as demonstrated by lineage-tracing studies. Mechanistically, chronic TNFα induced a distinct transcriptional program in single cell RNA sequencing of HSPCs and megakaryocytes. Together, these findings establish that chronic TNFα promotes hyperreactive platelet formation not through direct effects on megakaryocytes or MkPs but by expanding and transcriptionally reprogramming HSPCs, thereby imprinting a TNFα dependent program that persists through megakaryopoiesis and ultimately produces hyperreactive platelets.

Chronic TNFα exposure drives HSC expansion and myeloid biasing of progenitors.TNFα regulates platelet hyperreactivity by signaling through HSPCs, not Mks.