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Abstract: FR-PO702

Proteomic Analysis of Glomerular Extracellular Matrix Demonstrates Differences between FSGS Variants

Session Information

Category: Glomerular

  • 1002 Glomerular: Basic/Experimental Pathology

Authors

  • Merchant, Michael, University of Louisville, Louisville, Kentucky, United States
  • Caster, Dawn J., University of Louisville, Louisville, Kentucky, United States
  • Wilkey, Daniel Wade, University of Louisville, Louisville, Kentucky, United States
  • Barati, Michelle T., University of Louisville, Louisville, Kentucky, United States
  • McLeish, Kenneth R., University of Louisville, Louisville, Kentucky, United States
Background

Abnormal remodeling of glomerular extracellular matrix (ECM) is a prominent feature of focal segmental glomerular sclerosis (FSGS). Changes in ECM that accompany FSGS have not been defined in humans. We postulated that FSGS is characterized by specific changes in ECM composition. The current study used laser capture microdissection (LCMD) of glomeruli from human biopsy specimens and mass spectrometry (MS) and immunohistochemical (IHC) methods to compare -ECM composition among patients with FSGS-NOS, collapsing FSGS (CFSGS), and normal subjects.

Methods

Glomerular sections were obtained by LCMD from de-identified FFPE tissue from FSGS-NOS (n=6), CFSGS (n=7), and from 2 kidneys retrieved, but not used, for transplantation. Samples were analyzed as recently published (Hobeika L, et al. Characterization of glomerular extracellular matrix by proteomic analysis of laser-captured microdissected glomeruli. Kidney Int. 2017 91:501-511). Abundance data were filtered by GO annotation and matrixome designation for confirmatory IHC studies using Human Proteome Atlas validated antibodies and an expanded disease/normal- control renal biopsy panel.

Results

IHC was performed on 7 of 25 ECM proteins unique to CFSGS, 3 of 6 unique to FSGS-NOS, and 2 of 20 present in both subtypes of FSGS but not normal. All ECM proteins identified from normal were present in FSGS glomeruli. Annexin 3, marker of parietal epithelial cells (PEC), and cathepsin C, an inflammatory protease, showed intraglomerular staining in 10% to 20% of glomeruli in biopsies from CFSGS patients, while only staining Bowman’s capsule in biopsies of FSGS-NOS, minimal change disease, IgAN, primary membranous nephropathy, and congenital nephrotic syndrome. Annexin 3 and cathepsin C co-localized within CFSGS glomeruli, while staining with a marker of activated PEC (CD44), was negative.

Conclusion

PEC infiltration of glomerular tufts was characteristic of CFSGS, not FSGS-NOS. Although PEC did not express activation markers, they produced a protease unique to glomerular ECM. Cathepsin C may represent a novel mediator of PEC-mediated glomerulosclerosis leading to collapse.

Funding

  • NIDDK Support