Medium-dose irradiation impairs long-term hematopoietic stem cell functionality and hematopoietic resilience to...

Irradiation and 5-fluorouracil (5-FU) are widely utilized tools in hematopoietic research to generate myeloablation and assess blood recovery dynamics. A comprehensive understanding of their effects on the hematopoietic system is essential for optimizing therapeutic strategies, refining experimental models to modulate hematotoxicity, and interpreting research outcomes. Despite their widespread application, the long-term hematopoietic impacts of irradiation and 5-FU, particularly on hematopoietic stem cells (HSCs), remain incompletely characterized. In this study, we therefore examined the long-term effects of 2 Gy medium-dose ionizing radiation (MDIR) and 150 mg/kg 5-FU on HSCs and the hematopoietic system's resilience to subsequent cytotoxic stress in mice. Our findings demonstrate that MDIR, but not 5-FU, induces sustained impairments in HSC function and results in the selective depletion of MHC class II^- HSCs - a subset characterized by high self-renewal potential and hypersensitivity to irradiation-induced ROS production. Furthermore, MDIR significantly compromised hematopoietic recovery following a subsequent 5-FU challenge, as evidenced by substantially reduced platelet and red blood cell (RBC) counts during the critical recovery phase. These findings highlight the distinct and persistent impacts of MDIR and 5-FU on HSCs and hematopoietic function, revealing crucial differences in their mechanisms of action and long-term consequences on the hematopoietic system.