Segmental sclerosis is a characteristic lesion defining both primary and secondary glomerulosclerosis. In most diseases causing glomerulosclerosis, Tgfb expression in podocytes is a stress response signal associated with sclerosis lesions. To define precisely how activation of Tgfb type I receptor (TbrI) signaling in podocytes affects glomerular cells in vivo, we generated a transgenic mouse model (PodTbrI(AAD) that enables conditional (Doxycycline-inducible) expression of a constitutively-active TbrI mutant (TbrI(AAD). When TbrI(AAD) signaling is activated in podocytes, mice eventually develop albuminuria and subsequently progressive glomerulosclerosis associated with podocyte depletion. However, podocyte morphology remains normal while podocytes initially release endothelin 1 (Edn1) to cause endothelial cell mitochondrial oxidative stress (ENDO mtStress) and endothelial dysfunction (ED). Furthermore, treatment with an inhibitor of endothelin 1 type A receptor (Ednra) or mitochondrial-targeted superoxide scavenger, eliminated ENDO mtStress and prevented albuminuria and segmental sclerosis. These results suggest a novel podocyte-to-endothelial-to- podocyte crosstalk, where Edn1/Ednra meditated ENDO mtStress and ED is essential for manifestation of podocyte damage/loss in progressive sclerosis. Using in vitro co-culture system of PodTbrI(AAD) podocytes and mouse glomerular endothelial cells (mGECs), we confirmed that Dox-activated PodTbrI(AAD) conditioned medium or Edn1 treatment of mGEC was sufficient to initiate ED, and subsequent mGEC supernatant was sufficient to induce podocyte apoptosis. Finally, we timed Dox withdrawal and found that 100-fold increase of urine albumin/creatinine ratio and at least 40% loss of podocytes were phenotypic markers for irreversible progression of sclerosis even in the absence of Dox. HYPOTHESIS: Perturbation of podocyte homeostasis can be associated with Edn1 release to initiate Edn1/Ednra-mediated mtStress and dysfunction of adjacent endothelial cells, which in response release soluble signal(s) that mediate progressive damage and depletion of adjacent podocytes characteristic of progressive segmental sclerosis.
SPECIFIC AIMS : 1) Identify soluble molecular signal(s) produced by endothelial cells, subject to Edn1-activated dysfunction, that is required for manifestation of podocyte apoptosis in vitro. 2) Refine and pinpoint the phenotypic markers (thresholds) and the underlying molecular mechanisms that demarcate precisely the onset of irreversible progression of glomerulosclerosis in PodTbrI(AAD) mice. 3) Delineate whether segmental sclerosis and podocyte lesions in human primary and secondary podocytopathies are correlated with underlying podocyte-endothelial crosstalk in human kidney biopsy cases. LONGTERM: the proposed studies should elucidate the requirements and mechanisms for interdependent signaling crosstalk between dysregulated podocytes and endocapillary cells that determine irreversible segmental sclerosis characteristic of glomerular disease progression.
This research aims to identify novel glomerular lesion-specific therapeutic targets.

Public Health Relevance

Chronic kidney disease (CKD) affects one in ten Americans and is a major public health problem in the U.S., both in terms of disease burden and health expenditure. We developed a unique new animal model for studies proposed in this application to define cell-type specific characteristic cellular responses and signals of glomerular disease progression in CKD. In the longterm, these studies should lead to a better understanding of the cell damage mechanisms that promote progression of CKD in humans.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Pathobiology of Kidney Disease Study Section (PBKD)
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Rys-Sikora, Krystyna E
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Icahn School of Medicine at Mount Sinai
Internal Medicine/Medicine
Schools of Medicine
New York
United States
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Daehn, Ilse Sofia (2018) Glomerular Endothelial Cells Stress and Cross-Talk With Podocytes in the Development of Diabetic Kidney Disease. Front Med (Lausanne) 5:76
Qi, Haiying; Casalena, Gabriella; Shi, Shaolin et al. (2017) Glomerular Endothelial Mitochondrial Dysfunction Is Essential and Characteristic of Diabetic Kidney Disease Susceptibility. Diabetes 66:763-778
Daehn, Ilse (2016) Shift in Focus-To Explore the Role of the Endothelium in Kidney Disease. HSOA J Nephrol Ren Ther 2:
Casalena, Gabriella; Bottinger, Erwin; Daehn, Ilse (2015) TGF?-Induced Actin Cytoskeleton Rearrangement in Podocytes Is Associated with Compensatory Adaptation of Mitochondrial Energy Metabolism. Nephron 131:278-84
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Daehn, Ilse; Casalena, Gabriella; Zhang, Taoran et al. (2014) Endothelial mitochondrial oxidative stress determines podocyte depletion in segmental glomerulosclerosis. J Clin Invest 124:1608-21
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Gentle, Madeleine E; Shi, Shaolin; Daehn, Ilse et al. (2013) Epithelial cell TGF? signaling induces acute tubular injury and interstitial inflammation. J Am Soc Nephrol 24:787-99