Erythropoietin Plays a Protective Role in Submandibular Gland Hypofunction Induced by Irradiation

Abstract Purpose This study aims to explore the radioprotective effects of recombinant human erythropoietin (rhEPO) on rats’ submandibular gland hypofunction induced by irradiation. Materials and Methods Thirty rats were divided into 3 groups: (1) control group, (2) irradiation (IR) group, and (3) irradiation+rhEPO (IR+rhEPO) group. IR group and IR+rhEPO group received a single dose of 15 Grays (Gy) (0.98Gy/min), plus, IR+rhEPO group also received subcutaneous administration of rhEPO at a dose of 3,000 IU/kg body weight 3 days before irradiation and then repeated every 24 h for the first two weeks after irradiation. Immunohistochemistry analysis to erythropoietin receptor (EPOR) was performed to detect the levels of EPOR in submandibular glands with or without radiation. 90 days after irradiation, the salivary flow rates were assessed, and the submandibular gland of every rat was subjected to hematoxylin and eosin (H&E) staining and immunohistochemical staining with anti- Aquaporin 5 (AQP-5) and anti-proliferating cell nuclear antigen (PCNA) antibodies. Apoptosis was examined by the terminal deoxynucleotidyl transferase biotin-dUDP nick end labeling (TUNEL) assay. Additionally, to examine the protective role of rhEPO on human submandibular gland (HSG) cells, the apoptotic and proliferation rate of cells under a radiation dose of 8 Gy was detected. One-way analysis of variance (ANOVA) was carried out to analyze the results of each group, and the P value was set at 0.05. Results EPOR was expressed in the submandibular glands at a low level under normal condition, but upregulated after irradiation. rhEPO administration remarkably alleviated gland atrophy, increased salivary flow rates with upregulation of AQP-5 compared with IR group. Also, fewer apoptotic cells and more proliferative cells were observed in the IR+rhEPO group compared to the IR group, both in vivo and in vitro. Conclusion rhEPO administration may be a useful countermeasure to mitigate submandibular gland hypofunction following therapeutic radiation exposure.