造血干细胞和祖细胞（HSPC）移植是治疗许多良性和恶性造血系统疾病的一种治疗方法，也是基因治疗的平台。然而，对HSPC移植产品进行离体操作的需求增加受到了保持重要的自我更新和静止特性的限制。鞘脂代谢在保护这些重要细胞特性方面的作用最近被认识到，但尚未广泛探索。在这里, 我们证明了药理学和遗传学上抑制中性鞘脂磷脂酶-2（nSMase2）可以在离体培养后持续改善长期竞争性移植效能。从机制上讲, nSMase2的阻断激活了一个典型的集成应激反应（ISR），并促进了人类和小鼠HSPC的新陈代谢静止。部分原因是由鞘脂代谢紊乱导致nSMase2依赖的细胞外囊泡（EVs）的释放受阻所致。综合研究结果揭示了EV转运和ISR作为维护HSPC稳态和长期适应能力的调控二联体。翻译方面，短暂的nSMase2抑制能够增强HSPC的离体移植能力。版权所有© 2023美国血液学会。

Hematopoietic stem and progenitor cell (HSPC) transplantation serves as a curative therapy for many benign and malignant hematopoietic disorders, and as a platform for gene therapy. However, growing needs for ex vivo manipulation of HSPC graft products are limited by barriers in maintaining critical self-renewal and quiescence properties. The role of sphingolipid metabolism in safeguarding these essential cellular properties has been recently recognized, but not yet widely explored. Here we demonstrate that pharmacologic and genetic inhibition of neutral sphingomyelinase-2 (nSMase2) leads to sustained improvements in long-term competitive transplantation efficiency after ex vivo culture. Mechanistically, nSMase2 blockade activates a canonical integrated stress response (ISR) and promotes metabolic quiescence in human and murine HSPCs. These adaptations result in part from disruption in sphingolipid metabolism that impairs the release of nSMase2-dependent extracellular vesicles (EVs). The aggregate findings link EV trafficking and the ISR as a regulatory dyad guarding HSPC homeostasis and long-term fitness. Translationally, transient nSMase2 inhibition enables ex vivo graft manipulation with enhanced HSPC potency.Copyright © 2023 American Society of Hematology.