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Kidney Week

Abstract: TH-OR018

Twist1 in Macrophages Attenuates Kidney Fibrosis after Ureteral Obstruction

Session Information

Category: CKD (Non-Dialysis)

  • 1903 CKD (Non-Dialysis): Mechanisms

Authors

  • Ren, Jiafa, Duke University, Durham, North Carolina, United States
  • Lu, Xiaohan, Duke University, Durham, North Carolina, United States
  • Wen, Yi, Southeast University, Nanjing, China
  • Privratsky, Jamie, Duke University Medical Center, Durham, North Carolina, United States
  • Crowley, Steven D., Duke University Medical Center, Durham, North Carolina, United States
Background

Macrophages play a critical role in directing kidney fibrogenesis. The transcription factor Twist1 limits pro-fibrotic cytokine production in macrophages, and we have recently found that activating type 1 angiotensin receptors in macrophages induces Twist1 but paradoxically attenuates renal fibrosis. To directly test the role of macrophage Twist1 in kidney scar formation, we subjected mice with macrophage-specific deletion (“MKO”) of Twist1 and controls (“WT”) to the unilateral ureteral obstruction model.

Methods

C57BL/6 mice with a floxed allele for the gene encoding Twist1 were bred with LysM-Cre mice to yield Twist1 MKO mice with robust but selective deletion of Twist1 in macrophages (>80% vs. WTs; p < 0.0001). Twist1 MKO and WT littermate controls underwent unilateral ureteral ligation with assessment of kidney fibrosis and macrophage phenotype at 14 days.

Results

2 weeks after UUO, Twist1 MKO mice developed more kidney fibrosis compared to WTs as quantitated by western blots for collagen I (1.5 ± 0.1 vs 1.00 ± 0.1 au; p = 0.01) and α-SMA (1.5 ± 0.15 vs 1.00 ± 0.12 au; p = 0.01) and hydroxyproline assay (10.7 ± 0.8 vs 8.2 ± 0.6 mg/10mg; p = 0.02). As certain MMPs may limit renal fibrosis by degrading extracellular matrix, we profiled kidney MMP expression after UUO and found that the obstructed Twist1 MKO kidneys compared to WTs had blunted mRNA levels for MMP11 (0.65 ± 0. 05 vs 1.00 ± 0.13; p = 0.03) and MMP13 (0.38 ± 0.11 vs 1.00 ± 0.20; p = 0.03) but preserved expressions of MMP2 and 7 (0.90 ± 0.14 vs 1.1 ± 0.15; p = 0.78 and 0.84 ± 0.30 vs 1.0 ± 0.19; p = 0.66, respectively). Other gene expression patterns in the Twist1 MKO kidneys consistent with macrophage-driven fibrosis were blunted Arg-1 levels (0.14 ± 0.06 vs 1.00 ± 0.30; p = 0.05) and upregulation of Fizz1 (2.35 ± 0.69 vs 1.0 ± 0.19; p = 0.03). We therefore used flow cytometry to detect enhanced accumulation of CD11b+Ly6Chi infiltrating monocytes in the obstructed Twist1 MKO kidneys vs WTs (271 ± 41 vs 169 ± 17 cells/mg kidney; p = 0.049). Consistent with a role for Twist1 to suppress inflammatory cytokines in myeloid cells, LPS-stimulated peritoneal macrophages from the Twist1 MKO cohort had upregulated IFN-γmRNA compared to WTs (5.9 ± 0.3 vs 1.0 ± 0.2 au; p < 0.001).

Conclusion

Twist1 suppresses myeloid cell-dependent fibrosis in the kidney, possibly through effects on matrix degradation.

Funding

  • NIDDK Support