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Abstract: FR-OR40

Intravital Imaging Reveals Glomerular Capillary Enlargement and Endothelial/Immune Cell Activation Early in Alport Syndrome

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • Gyarmati, Georgina, University of Southern California Keck School of Medicine, Los Angeles, California, United States
  • Shroff, Urvi Nikhil, University of Southern California Keck School of Medicine, Los Angeles, California, United States
  • Izuhara, Audrey, University of Southern California Keck School of Medicine, Los Angeles, California, United States
  • Da Sacco, Stefano, University of Southern California Keck School of Medicine, Los Angeles, California, United States
  • Sedrakyan, Sargis, University of Southern California Keck School of Medicine, Los Angeles, California, United States
  • Cravedi, Paolo, Icahn School of Medicine at Mount Sinai Department of Medicine, New York, New York, United States
  • Amann, Kerstin U., Friedrich-Alexander-Universitat Erlangen-Nurnberg Medizinische Fakultat, Erlangen, Bayern, Germany
  • Lemley, Kevin V., University of Southern California Keck School of Medicine, Los Angeles, California, United States
  • Perin, Laura, University of Southern California Keck School of Medicine, Los Angeles, California, United States
  • Peti-Peterdi, Janos, University of Southern California Keck School of Medicine, Los Angeles, California, United States
Background

Alport syndrome (AS) is a rare genetic disorder caused by mutations in type IV collagen that lead to defective glomerular basement membrane, damage of the glomerular filtration barrier (GFB), and progressive kidney disease. While the genetics of AS is well known, the molecular and cellular mechanistic details of disease pathogenesis have been elusive, hindering the development of effective, specific, and mechanism-based therapies. Here we aimed to obtain direct visual clues on the major drivers of AS pathology by performing high-power intravital multiphoton microscopy (MPM) of the local kidney tissue microenvironment in a mouse model of AS, with translation to the human condition.

Methods

In vivo kidney MPM imaging of transgenic Alport mice (Col4α5 mutation) at 2 and 5 months of age was combined with urinalysis and histology. Endothelial glycocalyx was labeled with FITC-WGA, T cells with anti-CD3-Alexa594/CD44-Alexa488 antibodies, and plasma with Albumin-Alexa680. Animals received hyaluronidase (50U iv). AS patient renal biopsy specimens with minimal change disease controls were used for semithin and immunofluorescence histological analysis and single glomerular spatial proteomics (Nanostring).

Results

Severely distended glomerular capillaries and aneurysms were found in AS mice accompanied by numerous microthrombi, increased glomerular endothelial glycocalyx and immune cell homing, albumin leakage through the GFB, glomerulosclerosis and interstitial fibrosis by 5 months of age with an intermediate phenotype at 2 months. Histological and single glomerular spatial proteomics analysis of AS patient biopsies confirmed the presence of dilated glomerular capillaries, activated T cells, endothelial injury and inflammation. Acute treatment of AS mice with hyaluronidase reduced excess glomerular endothelial glycocalyx and blocked immune cell homing and albumin leakage through the GFB.

Conclusion

We identified the central roles of glomerular capillary mechanical strain, endothelial and immune cell activation early in AS in both mice and humans that may be therapeutically targeted to reduce local tissue injury and improve kidney function.

Funding

  • NIDDK Support