Elucidating Molecular Changes in Hematopoietic Stem Cells Following Chronic Salmonella Infection

Introduction: Hematopoietic stem cells (HSCs) are essential for maintaining blood and immune cell production by balancing self-renewal and differentiation. Typically residing in a quiescent state in the bone marrow (BM), HSCs become activated during injury or infections to replenish hematopoietic cells. Chronic infections, such as those caused by Salmonella, disrupt this balance, driving persistent inflammation that depletes HSC reserves, impairs functionality, and skews differentiation. This study investigates the impact of chronic Salmonella infection on HSCs, including functional changes, lineage bias, and recovery following antibiotic treatment, using a murine model and single-cell RNA sequencing (scRNA-seq).

Material and Methods: C57BL/6 and Fgd5-mCherry+ mice were infected via gavage with Salmonella x9088 to establish a chronic infection model. BM cells were collected and stained with Lineage Cocktail, Sca1, cKit and CD150 for flow cytometry and functional analysis. Transplantation assays involved injecting 500 CD45.2 HSCs from infected, healthy, or recovered mice alongside CD45.1 competitor cells into lethally irradiated F1(CD45.1 and CD45.2) recipients. Peripheral blood was analyzed at intervals up to 16 weeks. We performed scRNA-seq on purified HSCs to examine molecular changes across infection stages.

Results and discussion: Infected mice exhibited weight loss, splenomegaly, and HSC exhaustion, by reduced transplantation potency, compared to healthy controls. Antibiotic treatment, initiated seven days post-infection, restored weight and HSC functionality, suggesting recovery of hematopoietic balance. scRNA-seq revealed significant depletion of HSCs, particularly dormant HSCs (dHSCs), in infected mice. Chronic infection induced a myeloid differentiation bias. Post-treatment, HSC populations and transcriptional profiles returned to resemble those of healthy mice, indicating restoration of potency and lineage.

Conclusion: This study demonstrates that chronic Salmonella infection profoundly impacts HSC, driving inflammation-mediated activation, lineage skewing, and functional exhaustion. Antibiotic treatment effectively restores HSC potency, highlighting its therapeutic potential. These findings emphasize the broader consequences of chronic infections on stem cell biology and immune resilience, offering valuable insights into host-pathogen interactions and potential strategies to mitigate infection-induced hematopoietic dysfunction.