Figure 4.
Luminal debris induces bidirectional tubular cell:macrophage cross-talk to promote tubule proliferative repair. (A) Immunofluorescent staining of mouse kidney for F4/80 after IRI/CL-NX reveals that arginase-1 (green) is limited to the outer stripe of the outer medulla near sites of intraluminal casts. (OSOM, outer stripe of the outer medulla; ISOM, inner stripe of the outer medulla; arrows indicate casts). Scale bar, 20 μm. (B) Immunofluorescent staining of mouse kidney for GM-CSF shows expression in epithelial cells adjacent to intraluminal cell debris (casts) after IRI/CL-NX (arrows indicate GM-CSF staining, LTL indicates brush border staining). Scale bar, 10 μm. (C) Schematic of Transwell experiments showing PCRCs and cultured naïve BMMs. (D) Csf2 mRNA expression is significantly higher in PCRCs cultured with cell debris on the apical surface (****P<0.0001, ANOVA). (E) Arg1 mRNA expression is significantly higher in wild-type (WT) BMMs cocultured with PCRCs exposed to debris versus PCRCs alone. Arg1 expression is significantly reduced in Arg1mko macrophages (KO) (****P<0.0001, ***P<0.001, ANOVA). (F) PCRCs were seeded at 10,000 cells per well (t0) and treated with conditioned media from Transwell cultures containing the components indicated under each bar, and cell numbers were counted at 24 hours (t1) (***P<0.001, **P<0.01, ANOVA).