Interleukin-1α alters megakaryocyte maturation, promotes emperipolesis, and induces a distinct proteomic profile

Megakaryocytes (MKs) are large, polyploid cells and precursors of blood platelets. Interleukin (IL)-1α is a proinflammatory cytokine and a known mediator of emergency thrombopoiesis. However, its effect on MK maturation in vitro has not been studied in detail.

We aimed to investigate the phenotypical and molecular consequences of IL-1α-based MK maturation.

Murine bone marrows were cultured in the presence of IL-1α, in addition to thrombopoietin (TPO), in vitro and analyzed for MK maturation at days 3 and 5 of culture. Furthermore, proteome analysis of MKs cultured with IL-1α and/or TPO was performed.

IL-1α induced differentiation of a greater number of larger MKs with higher ploidy and increased the release of platelet-like particles, but had decreased expression of maturation markers. Interestingly, we found a significantly higher rate of emperipolesis, characterized by transiently present Ly6G+ neutrophils within the MK cytoplasm in early cultures, which was dependent on IL-1α. At later stages, IL-1α-cultured MKs were morphologically indistinguishable from TPO-cultured MKs, although they kept the ability to produce more platelet-like particles. Proteome analysis further revealed a significantly higher abundance of neutrophil-related proteins, antimicrobial peptides, and inflammation-related proteins in early-stage IL-1α-cultured MKs, a pattern that persisted throughout late maturation.

Taken together, these results shed light on the modulatory role of IL-1α on MK maturation, influencing not only platelet biogenesis but also promoting emperipolesis and an immune-driven proteomic MK phenotype.