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Kidney Week

Abstract: PO2469

Activation of EGFR in Myofibroblasts Promotes Renal Fibrosis in Unilateral Ureteral Obstruction

Session Information

Category: CKD (Non-Dialysis)

  • 2103 CKD (Non-Dialysis): Mechanisms

Authors

  • Pan, Yu, Vanderbilt University Medical Center, Nashville, Tennessee, United States
  • Cao, Shirong, Vanderbilt University Medical Center, Nashville, Tennessee, United States
  • Terker, Andrew S., Vanderbilt University Medical Center, Nashville, Tennessee, United States
  • Niu, Aolei, Vanderbilt University Medical Center, Nashville, Tennessee, United States
  • Wang, Yinqiu, Vanderbilt University Medical Center, Nashville, Tennessee, United States
  • Fan, Xiaofeng, Vanderbilt University Medical Center, Nashville, Tennessee, United States
  • Wang, Suwan, Vanderbilt University Medical Center, Nashville, Tennessee, United States
  • Zhang, Ming-Zhi, Vanderbilt University Medical Center, Nashville, Tennessee, United States
  • Harris, Raymond C., Vanderbilt University Medical Center, Nashville, Tennessee, United States
Background

In response to injury, renal fibroblasts and pericytes differentiate into highly specialized myofibroblasts, which are essential for maintaining kidney structural integrity. It is imperative to identify the molecular mechanism initiating and sustaining myofibroblast activation in order to identify novel therapeutics to stop or reverse kidney fibrosis. The activation of epidermal growth factor receptor (EGFR) plays an important role in mediation of recovery of epithelial integrity following ischemic acute kidney injury (AKI). However, sustained activation of EGFR triggers renal fibrogenesis after AKI. The role of EGFR in fibroblasts/myofibroblasts in development of renal fibrosis after severe AKI has not been previously investigated.

Methods

Both PDGFRβ-Cre/ERT2; mCherry mice (WT) and PDGFRβ-Cre/ERT2; mCherry; EGFRf/f mice (PDGFRβ EGFR-/-) were treated with tamoxifen 2 weeks before unilateral ureteral obstruction (UUO) was performed for 3 or 7 days. Quantification of proliferation of PDGFRβ-positive cells was determined at day 3 after UUO. PDGFRβ-positive cells were isolated using PDGFRβ antibody/IgG microbeads.

Results

EGFR mRNA in isolated renal PDGFRβ+ cells was increased >5-fold after 7d UUO. In PDGFRβ EGFR-/- mice, selective EGFR deletion was confirmed by >80% EGFR mRNA reduction in isolated renal PDGFRβ+ cells as well as absence of immunofluorescent EGFR expression in α-SMA+ myofibroblasts. Flow cytometry determined that renal CD45-CD31-PDGFRβ+EdU+ cells were markedly lower in PDGFRβ EGFR-/- mice than WT mice 3d after UUO. PDGFRβ EGFR-/- mice had markedly decreased renal fibrosis, indicated by Sirius red and Masson’s Trichrome staining, and increased mRNA and protein levels of profibrotic and fibrotic components including α-SMA, collagen I, collagen IV, IL-11, fibronectin, and PDGFRβ. Isolated PDGFRβ+ cells from PDGFRβ EGFR-/- mice also expressed less col1α1 and col4α1. Unexpectedly, the mRNA levels of proinflammatory cytokines, including Tnf, Il6, Il1α,Il1b, Ccl2, Ccl3, Il23α, Infγ, and Il12 in whole kidney tissue as well as in isolated renal myeloid cells were comparable between WT mice and PDGFRβ EGFR-/- mice.

Conclusion

In response to UUO, increased EGFR expression in PDGFRβ+ cells induces myofibroblast proliferation and differentiation to promote subsequent fibrosis.

Funding

  • NIDDK Support