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Kidney Week

Abstract: TH-PO567

Expression of an Anti-Fibrotic Molecule, Smad Anchor for Receptor Activation (SARA), Is Significantly Decreased in Kidneys of Patients with CKD

Session Information

Category: CKD (Non-Dialysis)

  • 2103 CKD (Non-Dialysis): Mechanisms

Authors

  • Liang, Xiaoyan, Northwestern University, Chicago, Illinois, United States
  • Chang, Anthony, UChicago Medicine, Chicago, Illinois, United States
  • Schnaper, H. William, Northwestern University, Chicago, Illinois, United States
  • Hayashida, Tomoko, Northwestern University, Chicago, Illinois, United States
Background

Fibrosis is a final common characteristics of chronic kidney disease regardless of the primary injury. Many means to prevent cellular fibrotic processes have been explored with little success to date. We recently reported at previous ASN meetings, that overexpressing SARA in pericytes, one of the progenitor cells for fibroblasts in fibrosing kidney, prevents them from transdifferentiating to fibroblasts, hence inhibits fibrosis in chemically-induced interstitial fibrosis model in mouse. These findings suggest a novel approach in preventing fibrosis at a step where a progenitor cell acquires scar forming phenotype. Here, we evaluated relevance of the findings in human patient samples.

Methods

Kidney sections were freshly cut from archived, formalin-fixed paraffin-embedded biopsy samples. Biopsy samples include 5 with focal and segmental glomerulosclerosis (FSGS), 5 with diabetic nephropathy and 5 non-fibrosing controls. Sections were stained with Alexa 647 conjugated anti-SARA antibody and DAPI and evaluated with Nikon A1 confocal microscope. Thereafter, tubulointerstitial area of the sections were dissected using Zeiss PALM laser-capture microdissection system, and total RNA was extracted following digestion with proteinase K. RNAs were pre-amplified for SARA and β-microglobulin with Bio Rad prime PCR system, and mRNA levels were quantified with real-time PCR.

Results

SARA was highly expressed in proximal tubular epithelial cells and cells in the interstitium in non-fibrosing controls. In contrast, it was barely detected in samples from patients with FSGS or diabetic nephropathy. Consistant with the findings with immunostaining, SARA mRNA levels were significantly lower in samples from patients with FSGS or diabetic nephropathy (P < 0.05, Fig 1).

Conclusion

These results, consistent with our animal models, suggest that loss of SARA is pathogenic in fibrosis. SARA could be a novel therapeutic target in human CKD

Funding

  • NIDDK Support