A new mouse model of immune-mediated podocyte injury

Podocytes play a major role in the initiation and progression of glomerular diseases and are a target of both immune-mediated and non-immune-mediated injury. To establish a mouse model of such injury, we preimmunized mice with Freunds adjuvant 5 days before intravenous injection of a rabbit polyclonal antibody directed against a murine podocyte cell line. For the next 7 weeks, we collected urine, serum, and kidney samples. Nephritic animals developed severe albuminuria, which was maximal on day 10. Histochemistry revealed diffuse mesangial matrix expansion. Mouse immunoglobulin G and complement were detected in a linear pattern along the glomerular filtration barrier and in the mesangial hinge region. Complement depletion, however, did not prevent proteinuria. Glomerular T cells were increased, whereas podocytes were significantly reduced. Glomerular foot processes were flattened in regions with mesangial matrix deposition as viewed by electron microscopy. Immunohistochemistry detected the injected anti-podocyte antibody exclusively at the glomerular tuft on all days examined. Immunoelectron microscopy localized the antibody to podocyte foot processes and the glomerular basement membrane, which was morphologically intact. This suggests that the podocyte was the main target of the antiserum. Our study establishes a new mouse model of immune-mediated podocyte injury.