In addition, in a unilateral ureteral obstruction-induced rat model, macrophages, especially M2-polarized macrophages, and proximal tubule cells, upregulated vascular endothelial cell growth factor-C (VEGF-C) expression via tumor nuclear factor-α (TNF-α) and transforming growth factor (TGF)-β, leading to lymphangiogenesis by activation of VEGF receptor-3 (VEGFR-3) on lymphatic endothelial cells8. This evidence concerns the gene FLT4 and Ureteral obstruction.