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Kidney Week

Abstract: TH-OR110

Bimodal Activation of Macrophages Promotes Proliferation Independent and Dependent Cyst Expansion in PKD

Session Information

Category: Genetic Diseases of the Kidney

  • 1001 Genetic Diseases of the Kidney: Cystic

Authors

  • Kakade, Vijayakumar R., Yale University, New Haven, Connecticut, United States
  • Cassini, Marcelo Ferreira, Yale University, New Haven, Connecticut, United States
  • Somlo, Stefan, Yale University, New Haven, Connecticut, United States
  • Cantley, Lloyd G., Yale University School of Medicine, New Haven, Connecticut, United States
Background

Macrophages progressively accumulate adjacent to cyst lining cells in PKD. Macrophage chemoattractant protein-1 (Mcp1) is highly upregulated at the time of cyst initiation following knock-out of Pkd1, and dual deletion of Mcp1 and Pkd1 in renal tubules results in less renal macrophages, slower cyst growth, preserved GFR and better survival than deletion of Pkd1 alone. The current study addresses the mechanisms by which the Mcp1-induced macrophages promote cyst growth.

Methods

Expression profiling was performed by qPCR using RNA from whole kidney and flow sorted macrophages. Multiphoton microscopy was used to analyze tubule morphology from doxycycline-treated Mcp1fl/flPkd1fl/flPax8rtTA;TetOCre mice (DKO) and Pkd1fl/flPax8rtTA;TetOCre mice (SKO). Tubular cell responses were analyzed using Ki67, BrdU, comet assay and anti-8OHdG staining.

Results

Macrophages that accumulate at cyst initiation (8 weeks age, 2 weeks after doxy induction) express high levels of proinflammatory cytokines Tnfa, Nos2 and IL12, correlating with increased tubular cell injury as judged by Kim1 expression (SKO dCt 0.002 vs DKO dCt 0.0005, p=0.002) and oxidative DNA damage (14.4% 8OHdG+ cells in SKO vs 3.6% in DKO, p=0.009). Analysis of tubular cell proliferation rates and tubule morphology in SKO and DKO kidneys during at cyst initiation shows that the macrophage-dependent component of cyst growth corresponds to decreased tubular epithelial area (tubular cell flattening consistent with injury) and enlarged tubule area (tubule/epithelial area ratio of 3.8±1.0 in SKO vs 1.04±0.02 in control and 1.4±0.5 in DKO p<0.0001) rather than proliferation. At the late cystic stage (18 weeks age), macrophages express high levels of the alternative activation genes Arg1 and Mrc1, with a 3-fold increase in Ki67+ cells in the presence of macrophages (6.4±0.6 in SKO vs. 1.8±0.8 in DKO, p<0.0001), correlating with a late acceleration in cyst growth in the SKO kidneys.

Conclusion

The results demonstrate two distinct effects of macrophages: early proinflammatory induction of tubule cell injury and tubule dilation that is proliferation independent and late alternative activation mediated induction of proliferation-dependent cyst growth.