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Abstract: PO1708

GBM Deposition of Collagen 3α1 in Alport Glomeruli by Mesangial Filopodia Injure Podocytes via Aberrant Signaling Through DDR1 and Integrin α2β1

Session Information

Category: Glomerular Diseases

  • 1201 Glomerular Diseases: Fibrosis and Extracellular Matrix

Authors

  • Cosgrove, Dominic E., Boys Town National Research Hospital, Omaha, Nebraska, United States
  • Wilhelm, Kevin, Boys Town National Research Hospital, Omaha, Nebraska, United States
  • Madison, Jacob D., Boys Town National Research Hospital, Omaha, Nebraska, United States
  • Meehan, Daniel T., Boys Town National Research Hospital, Omaha, Nebraska, United States
  • Delimont, Duane C., Boys Town National Research Hospital, Omaha, Nebraska, United States
Background

We have previously shown in In Alport mice that ETAR activation in mesangial cells results in sub-endothelial invasion of glomerular capillaries by mesangial filopodia. The filopodia deposit mesangial matrix in the GBM, including laminin 211 which activates NF-kB, resulting in induction of inflammatory cytokines culminating in tubulointerstitial fibrosis. Here we show that collagen 3α1 is also deposited in the GBM, where it contributes to podocyte injury through activation of DDR1 and integrin α2β1 receptor signaling.

Methods

Wild type and Alport kidneys from mice were dual immunostained with anti- collagen 3α1 and anti-laminin 211 antibodies and analyzed by confocal microscopy. Dual staining with anti-DDR1 and anti-collagen 3α1 was analyzed by super resolution microscopy (SR-SIM). Cultured murine Alport podocytes were overlaid with recombinant collagen 3α1 or not for 24 hours and RNA analyzed by RNA-seq. These same cells were subjected to Si-RNA knockdown for integrin α2 or DDR1 and the RNA analyzed by RNA-seq. Results from this study were compared with RNAseq from RNA isolated from 7-week-old wild type and Alport mouse glomeruli.

Results

Collagen 3α1 localized to the mesangium in wild type mice and was found in both the mesangium and in the GBM in Alport mice where it co-localized with laminin 211. SR-SIM showed that collagen 3α1 staining was juxtaposed to DDR1 staining on podocytes and thus available for binding podocyte receptors. Numerous genes associated with podocyte injury are up-regulated in both Alport glomeruli and GECs treated with collagen 3α1, including osteopontin, TGF-β1/2, and collagen 1α1 among many others. Knockdown of α2β1 integrin or DDR1 ameliorated induction of selective profibrotic genes in GECs treated with collagen 3α1.

Conclusion

Collagen 3α1 is deposited in the GBM by mesangial filopodia where it activates DDR1 and α2β1 receptors resulting in podocyte injury and likely contributing significantly to glomerular damage. This may explain why deletion of either DDR1 or α2β1 integrin in Alport mice ameliorates renal pathology.

Funding

  • Other NIH Support