Objective: To investigate the improving effect of human urine-derived stem cell-derived exosomes (USC-Exo) on the endothelial function and erectile function of male rats with diabetic ED (DED) and explore their action mechanism.
Methods: USC-Exo were extracted from the culture medium of USC by ultracentrifugation and identified. Cavernous sinus endothelial cells (CCEC) were collected from SD male rats and cultured in endothelial cell growth medium-2 (EGM-2) (the normal control group), EGM-2 + L-glucose at 25 mM (the high glucose group), EGM-2 + L-glucose at 25 mmol/L) + USC-Exo at 10 μg/ml (the Exo group), and EGM-2 + L-glucose at 25 mmol/L + USC-Exo at 10 μg/ml) + 3-methyladenine at 2 mmol/L (the 3-MA group), respectively. Changes of the autophagic flux in the CCECs transfected with mRFP-GFP-LC3 adenovirus were detected under the fluorescence microscope. The proliferation and tube-forming ability of the cells were assessed by CCK8 and Matrigel assays, respectively. DED was induced by intraperitoneal injection of streptozotocin in 10 of the rats, which were equally and randomly divided into a DED and an Exo group, and another 5 normal male rats were taken as controls. The rats in the normal and DED groups were injected intracavernously with 100 μl of PBS, and those in the Exo group with 100 μl of USC-Exo at the concentration of 1 μg/μl. Four weeks after treatment, the maximum intracavernous pressure (ICPmax) and mean arterial pressure (MAP) were measured, the endothelial marker CD31 detected by immunofluorescence assay, the expressions of the CD31, Beclin1 and LC3 I/II proteins examined by Western blot, and the number of autophagosomes in the cavernous endothelial cells determined under the transmission electron microscope.
Results: USC-Exo significantly increased the number of autophagosomes in the CCEC in the high glucose group compared with that in the normal controls (39.5 ± 6.2 vs 12.5 ± 5.4, P < 0.05). The expression of Beclin1 and proliferation of the CCEC were significantly higher in the Exo than in the high glucose group (P < 0.05). The autophagy inhibitor 3-MA evidently reversed the increasing effect of USC-Exo on the proliferation of the CCEC. The tube-forming ability of the CCEC was significantly increased in the Exo group compared with that in the high glucose group (15.3 ± 3.2 vs 6.3 ± 2.1, P < 0.05), which was also reversed in the 3-MA group. Both ICPmax and the ICPmax/MAP ratio were significantly higher in the Exo than in the DED group (［86.6 ± 12.6］ vs ［37.9 ± 10.9］ mmHg, P < 0.05; 89.3 ± 14.1 vs 41.7 ± 11.5, P < 0.05), and so were the expressions of CD31, Beclin1 and LC3 I/II (P< 0.05) and the number of autophagosomes in the cavernosal endothelial cells (3.7 ± 0.6 vs 1.0 ± 1.0, P < 0.05).
Conclusions: USC-Exo can significantly improve the endothelial and erectile functions of DED rats by increasing the autophagy of cavernosal endothelial cells.
Keywords: diabetic erectile dysfunction; urine-derived stem cell; exosome; autophagy; rat.