Immune signatures of megakaryocytes in persistent inflammation-immunosuppression and catabolism syndrome.

Persistent inflammation-immunosuppression and catabolism syndrome (PICS) is a severe condition that may follow sepsis and is characterized by ongoing inflammation and immune suppression, diminishing quality of life and potentially causing death. The role of megakaryocytes (MKs) in PICS, despite their association with thrombopoiesis, is not well understood. In this study, we use single-cell RNA sequencing to profile MKs in peripheral blood mononuclear cell samples obtained from 11 patients, including six with PICS, five with sepsis, and five healthy controls, to determine the diversity and molecular signatures of the MKs. Five subgroups of MKs are identified (MK1-MK5), and their proportions vary across the groups. MK1 and MK2 are predominant in PICS. Gene Ontology analysis shows that genes related to antigen processing and presentation and IL-17 signaling are enriched in MK1, whereas genes associated with platelet degranulation and neutrophil activation are enriched in MK2. Moreover, the expression level of CCL5 is markedly increased in MKs. Ligand-receptor analysis reveals dynamic interactions among MKs and T cells, B cells, natural killer cells, monocytes, and macrophages, suggesting a broad role of MKs in immune homeostasis. In PICS model mice, MKs regulate systemic inflammation by reducing the levels of the proinflammatory cytokines TNF-α and IL-17A and promoting lung tissue repair. Our findings establish MKs as essential components of the immune system in PICS and provide new insights into their potential as therapeutic targets for post-sepsis immune dysfunction.