INTRODUCTION AND OBJECTIVES: Congenital defects or other abnormalities in the intravesical ureter are the most common cause of vesicoureteral reflux (VUR). Minimally invasive endoscopic injections of bulking agents or autologous cells have been used to restore the normal structure and function of the vesicoureteral junction. However, current injectable agents do not provide a long-term solution for VUR due to volume reduction and subsequent weakening of the bulking effect with time. Similarly, when autologous cells are implanted, the cells at the center graft tend to apoptose soon after implantation due to inadequate blood supply. The goal of this study was to evaluate the effect of vascular endothelial growth factor (VEGF) overexpression on urine derived stem cell (USC) survival, growth and myogenic differentiation and to determine whether this technique could improve injection therapy for the correction of VUR.

METHODS: USC were obtained from 9 urine samples (5 healthy individual donors; ages from 3 to 27). USC were infected with adenovirus containing the human VEGF gene (VEGF+-USC). VEGF production was measured with ELISA. Then, VEGF+-USC (5x106cells) in 500 µl collagen type I gel were subcutaneously implanted into athymic mice. The implanted graft size, microvasculature formation, smooth muscle differentiation and innervation of VEGF+-USC were assessed histologically and with immunocytochemical staining on days 14 and 28 after injection.

RESULTS: VEGF expression in the culture medium reached peak levels on day 10 post-infection. When VEGF+-USC were implanted in vivo, the resulting grafts were larger and better vascularized compared to the grafts of non-VEGF infected cells. In addition, the total number of implanted cells expressing human nuclear markers was significantly higher in the VEGF+-USC group. More cells expressed endothelial markers (CD 31 and vWF) and smooth muscle markers (alpha-smooth muscle action, desmin and myosin) in the VEGF+-USC group on day 14. Finally, VEGF+-USC grafts contained more nerve fibers than the controls at day 28 after injection.

CONCLUSIONS: VEGF overexpression in grafted urine derived stem cells enhanced the in vivo survival of these cells and increased neovascularization in the grafts in the early stages of USC implantation. In addition, VEGF overexpression had an impact on the myogenic differentiation of USC and the number of new innervations within the graft. This approach might have important clinic implications for urological cell therapy for the treatment of VUR.

Source of Funding: None