Figure 1.

Expression of FSTL1 in fibrogenic kidneys.A, Fstl1 expression in sham-operated and UUO kidneys. The data were extracted from the bulk RNA-Seq dataset (46). The y-axis shows fragments per kilobase per million mapped fragments (FPKM) (n = 4 per group). B–D, mRNA and protein levels of FSTL1 in the kidneys of mice subjected to UUO. Eight-week-old male mice were subjected to UUO on the left ureters. Mice were sacrificed 1, 3, and 7 days after UUO surgery. Right kidneys (Ctrl) and left kidneys (UUO) were collected and analyzed for Fstl1 mRNA levels (B) or for FSTL1 protein levels (C). Quantitative analysis of FSTL1 protein levels was performed by densitometry (D). E and F, violin plots of Fstl1 gene expression in different cell populations of UUO kidneys and in the mesenchymal/stromal cell cluster marked by Pdgfrb. The data were extracted from the single-cell RNA-Seq dataset on the renal cortex of UUO kidneys (46). The y-axis shows the log-scale normalized read count. G and H, cellular localization of FSTL1 in mouse UUO kidneys and human kidneys with IgA nephropathy (IgAN). Frozen sections of kidneys collected 3 days (D3) after UUO surgery (G) or IgAN kidneys at grade III (H) were subjected to immunofluorescent staining for FSTL1 (red) and PDGFR-β (green). Red asterisks indicate nonspecific bands, and black asterisks indicate FSTL1-specific bands. GAPDH was used as the loading control for Western blotting, and Rpl19 was used as the internal control for real-time PCR. n = 4 for B. ∗p < 0.05; ∗∗p < 0.01; and ∗∗∗p < 0.001. FSTL1, follistatin-like 1; IgA, immunoglobulin A; PDGFR-β, platelet-derived growth factor receptor beta; UUO, unilateral ureteral obstruction.