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

Background: Megakaryocytes (MKs) are large, polyploid cells and precursors of blood platelets. Interleukin-1 alpha (IL-1α) is a pro-inflammatory cytokine and a known mediator of emergency thrombopoiesis. However, its effect on MK maturation in vitro has not been studied in detail OBJECTIVES: We aimed to investigate the phenotypical and molecular consequences of IL-1α-based MK maturation METHODS: 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 MK cultured with IL-1α and/or TPO was performed RESULTS: IL-1α induced differentiation of a greater number of larger MKs with higher ploidy, increased the release of platelet-like particles (PLP), 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 PLPs. 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.

Conclusion: 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.