Hematopoietic Stem and Progenitor Cells with Elevated Central Carbon Metabolism Drive the Aging Process in Human Bone Marrow

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Comprehensive proteomic studies have demonstrated a remarkable increase in abundance of proteins involved in central carbon metabolism of human hematopoietic stem and progenitor cells (HSPC) with age. Following this cue, we have shown that HSPCs from older subjects can be fractionated into three distinct subsets with high, intermediate, and low glucose uptake capacity (GU-high, GU-inter, GU-low). Single cell transcriptome (scRNA-seq) studies subsequently revealed that the GU-high subset is highly enriched for senescent cells in the HSPC compartment of older (>60 years) subjects but hardly detectable in young (<30 years) subjects. Pathway analyses of the scRNA-seq data showed a higher expression of genes involved in myeloid development, inflammation and stress response, DNA damage and repair, and activation of cell cycle checkpoint genes in the GU-high subset. Above all, the GU-high subset is equipped with activated anti-apoptotic, pro-survival mechanisms. The first goal of this project is to verify if anti-apoptosis is responsible for the survival advantage of senescent cells in the human HSPC compartment, and if elimination of this subset by inhibitors of anti-apoptotic factors may restore the functional integrity of aging human HSPCs. We have generated data showing that recurrent somatic mutations associated with clonal hematopoiesis of indeterminate potential (CHIP) are mainly present in GU-high subset. The second goal of this proposal is to simultaneously analyze (a) recurrent somatic mutations associated with CHIP, (b) transcriptome profile, and (c) central carbon metabolism in the same individual HSPCs to unambiguously link these processes. We will combine index-sort strategies to quantify glucose uptake with MutaSeq to interrogate transcriptome profile and somatic mutations in single cells. By determining the connections among these layers in the same cells we expect to gain relevant and mechanistic insight into the heterogeneity spectrum of senescent HSPCs with age and identify further novel targets for senolysis. It is highly likely that cellular senescence is a series of progressive and phenotypically diverse states subsequent to initial growth arrest. Whereas inhibition of pro-survival mechanisms using “senolytic” agents may represent one promising strategy, additional targets may be identified by our combined experimental design at a single cell level. Our proposal will therefore contribute to a better understanding of the heterogeneity of cellular senescent in the human HSPC compartment, and will serve as a guidance for a correspondingly targeted approach to the emerging field of “senotherapy”.