Urine podocin:nephrin mRNA ratio (PNR) as a podocyte stress biomarker.

Background: Proteinuria and/or albuminuria are widely used for noninvasive assessment of kidney diseases. However, proteinuria is a nonspecific marker of diverse forms of kidney injury, physiologic processes and filtration of small proteins of monoclonal and other pathologic processes. The opportunity to develop new glomerular disease biomarkers follows the realization that the degree of podocyte depletion determines the degree of glomerulosclerosis, and if persistent, determines the progression to end-stage kidney disease (ESKD).

Growth-dependent podocyte failure causes glomerulosclerosis.

Podocyte depletion leads to glomerulosclerosis, but whether an impaired capacity of podocytes to respond to hypertrophic stress also causes glomerulosclerosis is unknown. We generated transgenic Fischer 344 rats that express a dominant negative AA-4E-BP1 transgene driven by the podocin promoter; a member of the mammalian target of rapamycin complex 1 (mTORC1) pathway, 4E-BP1 modulates cap-dependent translation, which is a key determinant of a cell's hypertrophic response to nutrients and growth factors. AA-4E-BP1 rat podocytes expressed the transgene and had normal kidney histology and protein excretion at 100 g of body weight but developed ESRD by 12 months.

Angiotensin II-dependent persistent podocyte loss from destabilized glomeruli causes progression of end stage kidney disease.

Podocyte depletion is a major mechanism driving glomerulosclerosis. Progression is the process by which progressive glomerulosclerosis leads to end stage kidney disease (ESKD). In order to determine mechanisms contributing to persistent podocyte loss, we used a human diphtheria toxin transgenic rat model.