Figure 3. Macrophages in kidney.

Acute kidney injury can lead to tubular epithelial cell death and injury, resulting in macrophage recruitment and activation. Activated macrophages promote the activation of the Wnt pathway, as shown by the upregulation of Wnt7b in macrophages, which directs the proliferation of renal tubular epithelial cells; macrophages also secrete lipid transport protein 2(LCN-2), and apoptotic cells secrete sphingosine-1-phosphate to promote the secretion of more Lcn-2 by macrophages, which binds to iron ions for transport to epithelial cells and promotes epithelial cell differentiation.