De Zuani, M. | bioRxiv Science

bioRxiv2024

Sepsis induces long-term reprogramming of human HSPCs and drives myeloid dysregulation in sepsis survivors

Sepsis is a life-threatening condition characterised by an overwhelming immune response and high fatality. While most research has focused on its acute phase, many sepsis survivors remain immunologically weakened leaving them susceptible to serious complications from even mild infections. The mechanisms underlying this prolonged immune dysregulation remain unclear, limiting effective interventions. Here, we analysed whether sepsis induced long-term "training" in hematopoietic stem and progenitor cells (HSPCs), imprinting changes that persist in their myeloid progeny. Peripheral blood analysis of 8 sepsis survivors, 12 patients with septic shock, and 10 healthy donors revealed a significant expansion of CD38+ progenitors in survivors, with increases in megakaryocyte-erythroid and granulocyte-monocyte progenitors, and reduced mature neutrophil counts. This shift suggests impaired granulopoiesis, favouring immature, immunosuppressive granulocytes. Differentiated macrophages from survivors HSPCs exhibited impaired metabolic pathways after lipopolysaccharide stimulation, with downregulation of tricarboxylic acid cycle and glycolysis genes, indicating altered immune metabolism. Pathway analysis revealed enhanced type-I interferon (IFN) and JAK-STAT signalling in survivors macrophages, reflective of potentially tolerance-prone reprogramming. Finally, exposing healthy donor HSPCs to IFN{beta} during macrophage differentiation reduced HSPC proliferation, increased apoptosis, and induced a metabolic shift towards glycolysis over mitochondrial respiration. Together, these findings suggest that sepsis induces lasting reprogramming in HSPCs leading to myeloid progeny with altered immune memory that might drive immune dysregulation in survivors. These data open avenues to explore potential targets to better manage long-term immune alterations in sepsis survivors. KEY POINTSO_LISepsis induces long-term alterations in HSPCs, leading to the expansion of immature progenitors and metabolic dysregulation of their progeny. C_LIO_LIType-I IFN signalling reprograms macrophage differentiation, affecting their metabolic function and reducing cell proliferation. C_LI

immunology↗

bioRxiv2023

Single-cell multi-omics map of human foetal blood in Down's Syndrome

Downs Syndrome (DS) predisposes individuals to haematological abnormalities, such as increased number of erythrocytes and leukaemia in a process that is initiated before birth and is not entirely understood. To understand dysregulated hematopoiesis in DS, we integrated single-cell transcriptomics of over 1.1 million cells with chromatin accessibility and spatial transcriptomics datasets using human foetal liver and bone marrow samples from three disomic and 15 trisomic foetuses. We found that differences in gene expression in DS were both cell type- and environment-dependent. Furthermore, we found multiple lines of evidence that DS haematopoietic stem cells (HSCs) are "primed" to differentiate. We subsequently established a DS-specific map of enhancer-gene relationships in disomic and trisomic HSCs using 10X Multiome data. By integrating this map with genetic variants associated with blood cell variation, we discovered that trisomy restructured enhancer-gene maps to dysregulate enhancer activity and gene expression critical to erythroid lineage differentiation. Further, as DS mutations display a signature of oxidative stress, we validated both increased mitochondrial mass and oxidative stress in DS, and observed that these mutations preferentially fell into regulatory regions of expressed genes in HSCs. Altogether, our single- cell, multi-omic resource provides a high-resolution molecular map of foetal haematopoiesis in Downs Syndrome and indicates significant enhancer-gene restructuring giving rise to co- occurring haematological conditions.

genomics↗