Kidney Week

Abstract: TH-PO088

TGF-β Promotes Fibrosis After Severe AKI by Enhancing Renal Macrophage Infiltration

Session Information

• AKI: Inflammation, New Technologies, Omics
  October 25, 2018 | Location: Exhibit Hall, San Diego Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

• 103 AKI: Mechanisms

Authors

• Chung, Sungjin, Vanderbilt University Medical Center, Nashville, United States

Sungjin Chung,

• Overstreet, Jessica Marie, Vanderbilt University Medical Center, Nashville, Tennessee, United States

Jessica Marie Overstreet,

• Li, Yan, Vanderbilt University Medical Center, Nashville, Tennessee, United States

Yan Li,

• Wang, Yinqiu, Vanderbilt University Medical Center, Nashville, Tennessee, United States

Yinqiu Wang,

• Niu, Aolei, Vanderbilt University Medical Center, Nashville, Tennessee, United States

Aolei Niu,

• Gewin, Leslie S., Vanderbilt University Medical Center, Nashville, Tennessee, United States

Leslie S. Gewin,

• Zhang, Ming-Zhi, Vanderbilt University Medical Center, Nashville, Tennessee, United States

Ming-Zhi Zhang,

• Harris, Raymond C., Vanderbilt University Medical Center, Nashville, Tennessee, United States

Raymond C. Harris,

Background

TGF-β, a central mediator of renal fibrosis, signals through a heterotetrameric receptor complex composed of two type I and two type II transmembrane subunits. Although macrophages are implicated as mediators of renal fibrosis and produce TGF-β1, macrophage TGF-β1 deletion did not prevent fibrosis after severe renal I/R injury. The current studies investigated the role of macrophage TGF-β signaling in post AKI fibrosis.

Methods

Male C57BL/6 wild type (WT, Tgfbr2^f/f) or LysM-Cre;Tgfbr2^f/f (TGFßRII^-/-) mice underwent uninephrectomy plus 29 min renal I/R and were sacrificed after 4 weeks. Both in vitro and in vivo chemotaxis assays were performed.

Results

At 4 weeks after injury, there was increased renal expression of TGF-ß1 and tubulointerstitial fibrosis in WT mice. TGFßRII-/- mice had markedly decreased renal fibrosis and decreased renal macrophages. TGF-ß is a potent chemoattractant. The in vitro chemotactic response to a known chemotaxin, f-Met-Leu-Phe, was not different between isolated bone marrow monocytes (BMMs) from WT and TGFßRII-/- mice. Although TGF-ß was also a potent chemoattractant to WT BMMs, TGFßRII-/- BMMs did not respond. The SMAD inhibitor, SIS3, markedly inhibited the chemotactic response to TGF-ß in WT BMMs, but had minimal effect in TGFßRII-/- BMMs. To confirm these findings in an in vivo setting, we utilized a chemotaxis assay using matrigel plugs. Matrigel suffused with either f-Met-Leu-Phe or TGF-ß1 was injected subcutaneously into the subscapular regions of WT or TGFßRII-/- mice. After 6 days, f-Met-Leu-Phe induced equal numbers of macrophage infiltration into the matrigel plugs of WT and TGFßRII-/- mice. TGF-ß also induced matrigel macrophage infiltration in WT mice but not in TGFßRII-/- mice. To determine macrophage infiltration into post AKI kidneys, we determined the number of PKH26 labeled BMMs infiltrating into WT kidneys for 3 days 12 days after AKI. There were significantly more PKH26 labeled WT BMMs than TGFßRII-/- BMMs.

Conclusion

Macrophage TGFßRII deletion protects against the development of tubulointerstitial fibrosis following severe ischemic renal injury. Chemoattraction of macrophage to the injured kidney through a TGF-β/TGFßRII axis is a heretofore undescribed mechanism by which TGF-ß can mediate renal fibrosis during progressive renal injury.

Funding

• NIDDK Support