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Abstract: TH-OR082

Differential Expression of Parietal Epithelial Cell and Podocyte Extracellular Matrix Proteins in Focal Segmental Glomerulosclerosis and Diabetic Kidney Disease

Session Information

Category: Glomerular Diseases

  • 1201 Glomerular Diseases: Fibrosis and Extracellular Matrix

Authors

  • Chan, Gek Cher, University of Washington, Seattle, United States
  • Eng, Diana G., University of Washington, Seattle, Washington, United States
  • Miner, Jeffrey H., Washington University School of Medicine, St. Louis, Missouri, United States
  • Alpers, Charles E., University of Washington, Seattle, Washington, United States
  • Hudkins, Kelly L., University of Washington, Seattle, Washington, United States
  • Chang, Anthony, UChicago Medicine, Chicago, Illinois, United States
  • Pippin, Jeffrey W., University of Washington, Seattle, Washington, United States
  • Shankland, Stuart J., University of Washington, Seattle, Washington, United States
Background

The differential expression of extracellular matrix (ECM) protein isoforms in focal segmental glomerulosclerosis (FSGS) and diabetic nephropathy is not well defined. In activated parietal epithelial cells (PECs), upregulation of CD44 is associated with ECM expansion. PEC-derived ECM proteins include Laminin β1 (LAMB1), Perlecan and collagen type IV α2 (COL4A2). Podocyte-specific ECM proteins include Laminin β2 (LAMB2), Agrin and collagen type IV α4 (COL4A4). This study aimed to demonstrate differential ECM protein expression by PECs in experimental and human FSGS and diabetic nephropathy, and to determine if CD44 plays a role in regulating ECM protein expression.

Methods

FSGS was induced in CD44 null (CD44-/-) and wild-type mice, using a cytotoxic podocyte antibody. Kidney tissues were obtained at baseline and day 28 of FSGS. Diabetic BTBR ob/ob mice with leptin deficiency obesity mutation, ob, in which severe hyperglycemia manifested resulting in advanced diabetic nephropathy at 24 weeks of age, were used. BTBR non-diabetic wild-type mice of similar age acted as controls. Human biopsies of normal kidney, FSGS and diabetic nephropathy were analyzed.

Results

In normal mouse and human glomeruli, PEC-derived ECM proteins were found along the Bowman’s capsule while, podocyte-specific ECM proteins were found at the glomerular basement membrane. However, in experimental FSGS, LAMB1, Perlecan and COL4A2 staining were significantly increased in PECs, and there was de novo expressions of LAMB2 and Agrin along Bowman’s capsule. In diabetic ob/ob mice, as well as in human biopsies with FSGS and diabetic nephropathy, similar findings were observed. Because our previous results showed lower ECM expansion in CD44-/- mice, we compared the difference of each ECM protein between CD44-/- and wild-type mice, to determine if ECM expansion was CD44-dependent. Perlecan, COL4A2, LAMB2 and Agrin were significantly lower in CD44-/- mice, but not LAMB1 or COL4A4.

Conclusion

Therefore, CD44 plays a role in regulating ECM protein expression. Activated PECs result in increased PEC-derived matrix production, and de novo production of podocyte-specific matrix.

Funding

  • NIDDK Support