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J Am Soc Nephrol. 2020 Apr;31(4):799-816. doi: 10.1681/ASN.2019080827. Epub 2020 Feb 21.

Cellular and Molecular Mechanisms of Kidney Injury in 2,8-Dihydroxyadenine Nephropathy.

Author information

1
Institute of Pathology.
2
Division of Nephrology and Immunology.
3
Division of Nephrology.
4
Faculties of Medicine and.
5
Children's Medical Center, and.
6
Institute of Pathology, University Hospital Hamburg-Eppendorf, Hamburg, Germany; and.
7
Pharmaceutical Sciences, University of Iceland, Reykjavik, Iceland.
8
Department of Pathology Landspitali-The National University Hospital of Iceland, Reykjavik, Iceland.
9
Division of Nephrology, Klinikum der Universität, LMU München, Munich, Germany.
10
Biointerface Laboratory, Helmholtz Institute for Biomedical Engineering, and.
11
Institute of Pathology, pboor@ukaachen.de.
12
Department of Electron Microscopy, RWTH University Hospital Aachen, Aachen, Germany.

Abstract

BACKGROUND:

Hereditary deficiency of adenine phosphoribosyltransferase causes 2,8-dihydroxyadenine (2,8-DHA) nephropathy, a rare condition characterized by formation of 2,8-DHA crystals within renal tubules. Clinical relevance of rodent models of 2,8-DHA crystal nephropathy induced by excessive adenine intake is unknown.

METHODS:

Using animal models and patient kidney biopsies, we assessed the pathogenic sequelae of 2,8-DHA crystal-induced kidney damage. We also used knockout mice to investigate the role of TNF receptors 1 and 2 (TNFR1 and TNFR2), CD44, or alpha2-HS glycoprotein (AHSG), all of which are involved in the pathogenesis of other types of crystal-induced nephropathies.

RESULTS:

Adenine-enriched diet in mice induced 2,8-DHA nephropathy, leading to progressive kidney disease, characterized by crystal deposits, tubular injury, inflammation, and fibrosis. Kidney injury depended on crystal size. The smallest crystals were endocytosed by tubular epithelial cells. Crystals of variable size were excreted in urine. Large crystals obstructed whole tubules. Medium-sized crystals induced a particular reparative process that we term extratubulation. In this process, tubular cells, in coordination with macrophages, overgrew and translocated crystals into the interstitium, restoring the tubular luminal patency; this was followed by degradation of interstitial crystals by granulomatous inflammation. Patients with adenine phosphoribosyltransferase deficiency showed similar histopathological findings regarding crystal morphology, crystal clearance, and renal injury. In mice, deletion of Tnfr1 significantly reduced tubular CD44 and annexin two expression, as well as inflammation, thereby ameliorating the disease course. In contrast, genetic deletion of Tnfr2, Cd44, or Ahsg had no effect on the manifestations of 2,8-DHA nephropathy.

CONCLUSIONS:

Rodent models of the cellular and molecular mechanisms of 2,8-DHA nephropathy and crystal clearance have clinical relevance and offer insight into potential future targets for therapeutic interventions.

KEYWORDS:

TNFR; adenine associated nephropathy; extratubulation; renal fibrosis; tubular injury; tubulointerstitial inflammation

PMID:
32086278
DOI:
10.1681/ASN.2019080827

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