Impairment of podocyte function by diphtheria toxin—a new reversible proteinuria model in mice

Abstract

Diphtheria toxin (DTx) receptor (DTR)-mediated conditional cell ablation in transgenic mice is a powerful tool to analyze cell function in vivo. Transgenic mice with cell-specific expression of the human DTR have been developed that allow conditional depletion of these cells in vivo through administration of the toxin. We have performed a careful analysis of mice after DTx injection and found an unexpected side effect. Treatment of wild-type C57BL/6 mice with DTx leads to a marked transient and completely reversible proteinuria, as a consequence of podocyte dysfunction that is morphologically characterized by foot process fusion and detachment from the glomerular basal membrane. In vitro analysis displayed that DTx-treated podocytes show diminished attachment to basal membrane proteins. Five to 9 days after DTx application the mice recover completely. Glomerular proteinuria is a hallmark of glomerular disease due to dysfunction of the filtration barrier. Rodents have been extensively used experimentally to better define the mechanisms of disease induction and progression. However, nongenetic mouse models of proteinuric glomerular damage are limited and display various shortcomings. We suggest DTx-induced transient kidney dysfunction as a new reversible model of experimental podocyte injury, which could be used as an additional approach to complement studies in human.

Deficiency of Fibroblast Growth Factor-Inducible 14 (Fn14) Preserves the Filtration Barrier and Ameliorates Lupus Nephritis

“…52 Indeed, previous studies showed that changes in junction proteins may cause death of podocytes directly in addition to affecting podocyte function. 53 Moreover, TWEAK/Fn14 activation downregulates ZO-1 expression by endothelial cells. 54 Nevertheless, this latter study was performed in cells derived from human brain microvascular endothelium rather than the physiologically distinct murine glomerular endothelial cells studied here.…”

Animal models of kidney inflammation in translational medicine

“…Albeit not of use in drug development, such models were extremely helpful to validate the significance of podocyte loss for several histopathological glomerular lesions and the significance of podocyte loss for glomerulosclerosis and nephron loss [30]. However, diphtheria toxin induces proteinuria in mice also in the absence of any toxin receptor transgene [31]. Models of toxic mesangiolysis and subsequent mesangial hypercellularity with sclerosis include the rat anti-Thy-1.1 model and the Habu snake venom-induced injury in mice [32,33].…”

Tubulointerstitial fibrosis can sensitize the kidney to subsequent glomerular injury

“…Tubule-specific injury and glomerulus (podocyte)-specific injury were induced serially, using mice expressing two different toxin receptors on their proximal tubular epithelial cells (DTR) and podocytes (Nep25), respectively. 10–12 Acute tubular injury induced by DT was allowed to recover clinically in Nep25 + /DTR + mice. Although the resulting tubulointerstitial fibrosis was very mild, the subsequent glomerular injury, induced by injection of a separate podocyte-specific toxin, was more severe in these Nep25 + /DTR + mice vs Nep25 + /DTR − mice without such preexisting tubular injury.…”

“…Injury is present in the proximal tubule without glomerular change, and injured tubular cells recover rapidly. 10, 11 Glomerular-specific injury is possible in the so-called Nep25 mouse model, through selective podocyte injury by injection of a modified toxin, LMB2, in mice that express human CD25 only on podocytes, driven by the nephrin promotor. These mice show progressive nonselective proteinuria, with resulting edema, and focal segmental glomerulosclerosis due to podocyte injury.…”