Periostin promotes polarization of kidney macrophages to a proregenerative phenotype. (A) mRNA expression of different markers in F4/80+ macrophages isolated from control and periostin-overexpressing mice 72 hours after I/R. Macrophages from periostin-overexpressing mice show decreased levels of IL-6 and higher levels of CD163, IL-10, CSF-1, uPA, and LIF; indicating a polarization to a M2c regenerative phenotype. (B) Western blots and quantifications of different proteins in F4/80+ macrophages 72 hours after I/R. Macrophages from periostin-overexpressing mice produce higher levels of CD163, a M2c marker, and the trophic proregenerative factors LIF and uPA. (C) CD206+ macrophages in the kidney and (D) IL-10 expression levels in isolated renal macrophages are lower in periostin KO mice after I/R, showing a decreased M2 polarization. (E) mRNA expression of different factors in RAW macrophages cocultured with primary tubular cells for 48 hours at normal conditions (normoxia) or after subjection of cells to mineral oil–induced hypoxia. RAW macrophages cocultured with periostin-overexpressing tubular cells express lower levels of IL-6 and higher levels of heparin-binding EGF-like growth factor (HB-EGF), uPA, and LIF, only after coculture with cells subjected to hypoxia. (F) Macrophages show increased protein production of uPA and LIF after coculture with periostin-overexpressing tubular cells subjected to hypoxia, compared with coculture with control cells. (G) p-H3 staining and quantification, showing a higher induction in the proliferation of macrophages after coculture with hypoxia-treated tubular cells overexpressing periostin. Representative images are shown. Scale bars, 100 μm. *P<0.05, **P<0.01 versus RAW; #P<0.05, ##P<0.01 versus CNT I/R, WT I/R, or RAW + Cnt tubules. n=5 mice per group. For cell cultures, quantifications of two to three independent experiments performed in duplicate or triplicate are shown. GAPDH, glyceraldehyde-3-phosphate dehydrogenase; HPRT, hypoxanthine-guanine phosphoribosyltransferase.