Abstract: Objective: To observe the effect of hypoxic pretreatment of human amniotic mesenchymal stem cells (HP-hAMSCs) on the repair of salivary gland radiation function damage in SD rats. Methods: Exosomes of normal oxygen and hypoxia pretreated human amniotic mesenchymal stem cells (Nor-hAMSCs and HP-hAMSCs) were isolated and identified by kit method. Electron linear accelerator 18 Gy one-time irradiation was used to build a model of salivary gland damage in rats. Seventy-two 6-8 weeks SD rats were randomly divided into Control group, PBS group, NExos group, and HExos group, respectively, with 18 in each group. Seven, 14, and 28 days after irradiation, the weight and saliva volume of 6 rats were measured, and the glands were observed. Immunohistochemical staining was used to detect the expression of aquaporin 5 (AQP5). Results: The weight and saliva volume of rats in the NExos group and HExos group were higher than those in the PBS group. The amount of saliva in the HExos group was higher than that in the NExos group, and the weight of rats in the HExos group was higher than that in the NExos group at days 7 and 28 (P<0.05). HE staining of submandibular gland tissue showed that the glands in the HExos group had the strongest repair capacity. Quantitative analysis of AQP5 expression in submandibular glandular tissue showed that the optical density values of HExos group and NExos group increased at day 14 and 28 compared with those of PBS group (P<0.05), and the optical density value of HExos group was higher than that of NExos group (P<0.05). Conclusion: HP-hAMSCs exosomes can effectively repair the salivary secretion function of the salivary glands damaged by radiation.

Key words: human amniotic mesenchymal stem cells, hypoxic preconditioning, salivary glands, radiation damage, exosomes