DKK2 and diabetes mellitus: A close relationship between pericyte dysfunction and ED, especially ED caused by diabetes and nerve injury, has been recently reported.28 For example, DKK2 (dickkopf WNT signaling pathway inhibitor 2) mediates the interaction between pericytes and endothelial cells and promotes neurovascular regeneration in diabetic ED through the angiopoietin (Ang1)-Tie2 pathway.14 In addition, PC-NVs promote penile erection in diabetic ED mice in a lipocalin 2 (Lcn2)-dependent manner.23 However, studies of the role of pericytes in ED are still in their infancy and details are lacking.