3056 – VITAMIN C LIMITS MULTIPOTENT PROGENITOR SELF-RENEWAL AND CLONAL EXPANSION

Abstract

A fundamental question is whether physiological variations in diet-derived metabolite levels in vivo influence stem and progenitor cell self-renewal. Ascorbate (vitamin C) is enriched in hematopoietic stem cells (HSCs) and multipotent progenitors (MPPs) compared to all other hematopoietic cells, and ascorbate depletion increases the frequency of functional HSCs in bone marrow by reducing Tet2 function (Agathocleous et al., 2017). However, whether ascorbate regulates the self-renewal of other hematopoietic progenitors downstream of HSCs is still unknown.To answer this question, we conditionally deleted Slc23a2, the main hematopoietic ascorbate transporter. Competitive bone marrow transplantation revealed that deletion of the ascorbate transporter substantially increased donor-derived contribution compared to controls. Interestingly, Slc23a2 deletion only mildly increased donor chimerism in HSCs, while it significantly increased donor chimerism in MPPs, suggesting that ascorbate depletion enhances MPP self-renewal. Accordingly, deletion of the ascorbate transporter significantly increased donor reconstitution and the fraction of animals with long-term tri-lineage reconstitution upon competitive transplantation of purified MPPs. Moreover, in a model of in situ cell competition by chimeric deletion of the ascorbate transporter in HSCs and MPPs using Fgd5-CreER, ascorbate depletion accelerated the expansion of Slc23a2 mutant cells only downstream of MPPs. Taken together, these data demonstrated that ascorbate cell-autonomously restricts the self-renewal and clonal expansion of MPPs in the hematopoietic system. Our study thus points to a central role for diet-derived nutrients in the regulation of HSC and hematopoietic progenitor self-renewal abilities. Additionally, our data suggest that nutrition might directly impact the expansion of mutant cells in clonal hematopoiesis. A fundamental question is whether physiological variations in diet-derived metabolite levels in vivo influence stem and progenitor cell self-renewal. Ascorbate (vitamin C) is enriched in hematopoietic stem cells (HSCs) and multipotent progenitors (MPPs) compared to all other hematopoietic cells, and ascorbate depletion increases the frequency of functional HSCs in bone marrow by reducing Tet2 function (Agathocleous et al., 2017). However, whether ascorbate regulates the self-renewal of other hematopoietic progenitors downstream of HSCs is still unknown.To answer this question, we conditionally deleted Slc23a2, the main hematopoietic ascorbate transporter. Competitive bone marrow transplantation revealed that deletion of the ascorbate transporter substantially increased donor-derived contribution compared to controls. Interestingly, Slc23a2 deletion only mildly increased donor chimerism in HSCs, while it significantly increased donor chimerism in MPPs, suggesting that ascorbate depletion enhances MPP self-renewal. Accordingly, deletion of the ascorbate transporter significantly increased donor reconstitution and the fraction of animals with long-term tri-lineage reconstitution upon competitive transplantation of purified MPPs. Moreover, in a model of in situ cell competition by chimeric deletion of the ascorbate transporter in HSCs and MPPs using Fgd5-CreER, ascorbate depletion accelerated the expansion of Slc23a2 mutant cells only downstream of MPPs. Taken together, these data demonstrated that ascorbate cell-autonomously restricts the self-renewal and clonal expansion of MPPs in the hematopoietic system. Our study thus points to a central role for diet-derived nutrients in the regulation of HSC and hematopoietic progenitor self-renewal abilities. Additionally, our data suggest that nutrition might directly impact the expansion of mutant cells in clonal hematopoiesis.