SMAD3 and renal fibrosis: In the kidneys of UUO mice, MCP-1 expression is increased.[59] In Smad3 knockout mice, inhibition of MCP-1-dependent macrophage infiltration may be a mechanism to alleviate renal fibrosis in UUO mice.[60] MCP-1/CCR2 axis may be one of the main pathways of Twist1-mediated renal fibrosis in UUO mice.[39] Infiltration of CCR2-positive macrophages was decreased in UUO mice, in which the N-terminus of MCP-1 was deleted.[61]