Session: 501. Hematopoietic Stem and Progenitor Cells and Hematopoiesis: Basic and Translational: Disease and Aging
Hematology Disease Topics & Pathways:
Research, Fundamental Science, adult, elderly, bioinformatics, hematopoiesis, pediatric, neonatal, computational biology, young adult , Biological Processes, Technology and Procedures, Human, Study Population, omics technologies
To mechanistically interrogate the impact of immune activation on human HSCs, CD34+CD38-CD45RA–CD19– cells were isolated from control, TNFα, and LPS treated xenografts, after the 2.5 month recovery period at 20w, and subject to joint scRNA-seq and scATAC-seq profiling through the 10x Multiome platform. Within cells classified as HSCs/multipotent progenitors (MPPs), we identified two transcriptionally and epigenetically distinct subsets: homeostatic HSC (HSC-H) and memory HSC (HSC-M). HSC-H are enriched for canonical HSC programs we previously identified, that are involved in and actively sustain the human graft, whilst HSC-M primarily reside outside the trajectory of hematopoietic development (Fig A). Differential expression (DE) and differential accessibility (DA) analysis revealed that HSC-M cells experienced dramatic changes between PBS and TNFα treatment pertaining to gene expression (134 DE genes), chromatin accessibility (5660 DA peaks), and enrichment for transcription factor (TF) binding sites (116 TFs). By contrast, HSC-H cells experienced minimal changes between PBS and TNFα treatment (35 DE genes, 379 DA peaks, 13 TFs). We observed similar trends when comparing PBS and LPS treatments. In particular, binding sites of TFs within the AP-1 complex are enriched in HSC-M versus HSC-H, with the magnitude of this enrichment being more pronounced following TNFα or LPS treatment. Notably, a transcriptional signature specific to long-lived human memory T cells following yellow fever vaccination (Akondy et al, 2017) was highly enriched in HSC-M versus HSC-H cells following inflammatory stress (Fig. B). Additionally, human bone marrow HSC signatures enriched in elderly (70-80y) compared to young (20-30y) donors (generated from in-house scMultiome profiles and validated with scRNA-seq data from Ainciburu et al, 2022) were also enriched in HSC-M versus HSC-H cells isolated from our immune activation xenotransplantation model (Fig. B). Further, an HSC-M-specific transcriptional signature is capable of stratifying human HSCs by age, wherein CB HSCs show the lowest HSC-M signature enrichment and HSCs from older donors (>50y) show the highest HSC-M signature enrichment (50s vs 20s classification AUC = 0.95; 70s vs 20s classification AUC = 0.80). Our mechanistic multiome data points to a set of transcription factors and epigenetic determinants that represent candidates for encoding memory at the HSC level. Overall, these studies point to the discovery of a novel memory HSC pool that may potentially link infection history to human aging, with translational implications of HSC as sensors of inflammatory activation in age-related clonal hematopoiesis and origin of leukemogenesis.
Disclosures: Dick: Graphite Bio: Membership on an entity's Board of Directors or advisory committees; Trillium Therapeutics/Pfizer: Patents & Royalties: patent licencing; Celgene/BMS: Research Funding.
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