Purine metabolism in bone marrow microenvironment inhibits hematopoietic stem cell differentiation under microgravity

• Microgravity promotes HSC expansion in bone marrow by inhibiting cell cycle progression and reducing apoptosis. • Microgravity suppresses differentiation and function of hematopoietic stem/progenitor cells (HSPCs). • Microgravity alters purine metabolism in the bone marrow microenvironment, affecting MAPK signaling and hematopoietic cell lineage. • Hypoxanthine acts as a signaling mediator under microgravity, modulating HSC fate and offering potential therapeutic targets for spaceflight-induced hematopoietic disorders.