Radiation therapy can cause haematopoietic damage, and mesenchymal stem cells (MSCs) derived extracellular vesicles (EVs) have been shown to reverse this damage. Our previous research showed that dental pulp stem cells (DPSCs) have a strong proliferation capacity and can produce abundant amounts of EVs to meet the requirements for use in vitro and in vivo. DPSCs derived EVs (DPSCs-EVs) are evaluated for their effect on reducing haematopoietic damage. Haematopoietic stem cell (HSC) numbers and function were assessed by flow cytometry, peripheral blood cell counts, histology and bone marrow transplantation. Epidermal growth factor (EGF) was used as a reference for evaluating the efficiency of EVs. miRNA microarray was employed to find out the changes of miRNA expression after cells being irradiated in vivo and the role they may play in mitigation the radiation caused injury. We observed the effect of DPSCs-EVs on promoting proliferation and inhibiting apoptosis of human umbilical vein endothelial cells (HUVECs) and FDC-P1 cells in vitro. We found that DPSCs-EVs and EGF could comparably inhibit the decrease in WBC, CFU count and KSL cells in vivo. We also verified that EVs could accelerate the recovery of long-term HSCs. In summary, DPSCs-EVs showed an apoptosis resistant effect on HUVECs and FDC-P1 cells after radiation injury in vitro. EVs from DPSCs were comparable to EGF in their ability to regulate haematopoietic regeneration after radiation injury in vivo. Radiation could alter the expression of some miRNAs in bone marrow cells, and EVs could correct these changes to some extent.

Graphical abstract

放射治疗会导致造血损伤，而间充质干细胞 (MSCs) 衍生的细胞外囊泡 (EVs) 已被证明可以逆转这种损伤。我们之前的研究表明，牙髓干细胞（DPSCs）具有很强的增殖能力，可以产生大量的EV，以满足体外和体内使用的要求。评估了 DPSCs 衍生的 EVs (DPSCs-EVs) 对减少造血损伤的影响。通过流式细胞术、外周血细胞计数、组织学和骨髓移植评估造血干细胞 (HSC) 的数量和功能。表皮生长因子 (EGF) 被用作评估 EV 效率的参考。miRNA微阵列用于研究细胞在体内照射后miRNA表达的变化以及它们在减轻辐射损伤中可能发挥的作用。我们在体外观察了DPSCs-EVs促进人脐静脉内皮细胞（HUVECs）和FDC-P1细胞增殖和抑制凋亡的作用。我们发现 DPSCs-EVs 和 EGF 可以相当地抑制体内 WBC、CFU 计数和 KSL 细胞的减少。我们还验证了电动汽车可以加速长期 HSC 的恢复。总之，DPSCs-EVs 在体外辐射损伤后对 HUVECs 和 FDC-P1 细胞表现出抗凋亡作用。来自 DPSCs 的 EV 在体内辐射损伤后调节造血再生的能力与 EGF 相当。辐射可以改变一些 miRNA 在骨髓细胞中的表达，

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