Kidney diseases, including acute kidney injury (AKI) and chronic kidney disease (CKD), which can progress to end stage renal disease (ESRD), are a worldwide health burden. Organ transplantation or kidney dialysis are the only effective available therapeutic tools. Therefore, in vitro models of kidney diseases and the development of prospective therapeutic options are urgently needed. Within the kidney, the glomeruli are involved in blood filtration and waste excretion and are easily affected by changing cellular conditions. Puromycin aminonucleoside (PAN) is a nephrotoxin, which can be employed to induce acute glomerular damage and to model glomerular disease. For this reason, we generated kidney organoids from three iPSC lines and treated these with PAN in order to induce kidney injury. Morphological observations revealed the disruption of glomerular and tubular structures within the kidney organoids upon PAN treatment, which were confirmed by transcriptome analyses. Subsequent analyses revealed an upregulation of immune response as well as inflammatory and cell-death-related processes. We conclude that the treatment of iPSC-derived kidney organoids with PAN induces kidney injury mediated by an intertwined network of inflammation, cytoskeletal re-arrangement, DNA damage, apoptosis and cell death. Furthermore, urine-stem-cell-derived kidney organoids can be used to model kidney-associated diseases and drug discovery.

The lean body weight phenotype of hepatic lipase (HL)–deficient mice ( hl −/−) suggests that HL is required for normal weight gain, but the underlying mechanisms are unknown. HL plays a unique role in lipoprotein metabolism performing bridging as well as catalytic functions, either of which could participate in energy homeostasis. To determine if both the catalytic and bridging functions or the catalytic function alone are required for the effect of HL on body weight, we studied ( hl −/−) mice that transgenically express physiologic levels of human (h)HL (with catalytic and bridging functions) or a catalytically‐inactive (ci)HL variant (with bridging function only) in which the catalytic Serine 145 was mutated to Alanine. As expected, HL activity in postheparin plasma was restored to physiologic levels only in hHL‐transgenic mice ( hl −/− hHL) . During high‐fat diet feeding, hHL‐transgenic mice exhibited increased body weight gain and body adiposity relative to hl −/− ciHL mice. A similar, albeit less robust effect was observed in female hHL‐transgenic relative to hl −/− ciHL mice. To delineate the basis for this effect, we determined cumulative food intake and measured energy expenditure using calorimetry. Interestingly, in both genders, food intake was 5–10% higher in hl −/− hHL mice relative to hl −/− ciHL controls. Similarly, energy expenditure was ~10% lower in HL‐transgenic mice after adjusting for differences in total body weight. Our results demonstrate that (1) the catalytic function of HL is required to rescue the lean body weight phenotype of hl −/− mice; (2) this effect involves complementary changes in both sides of the energy balance equation; and (3) the bridging function alone is insufficient to rescue the lean phenotype of hl −/− ciHL mice. J. Chen, K. J. Kaiyala, J. Lam, N. Agrawal, L. Nguyen, K. Ogimoto, D. Spencer, G. J. Morton, M. W. Schwartz, H. L. Dichek, # In vivo structure‐function studies of human hepatic lipase: the catalytic function rescues the lean phenotype of HL‐deficient ( hl −/−) mice {#article-title-2}. Physiol Rep, 3(4), 2015, e12365, doi: 10.14814/phy2.12365

Urine has become the source of choice for noninvasive renal epithelial cells and renal stem cells which can be used for generating induced pluripotent stem cells. The aim of this study was to generate a 3D nephrogenic progenitor cell model composed of three distinct cell types—urine-derived SIX2-positive renal progenitor cells, iPSC-derived mesenchymal stem cells, and iPSC-derived endothelial cells originating from the same individual. Characterization of the generated mesenchymal stem cells revealed plastic adherent growth and a trilineage differentiation potential to adipocytes, chondrocytes, and osteoblasts. Furthermore, these cells express the typical MSC markers CD73, CD90, and CD105. The induced endothelial cells express the endothelial cell surface marker CD31. Upon combination of urine-derived renal progenitor cells, induced mesenchymal stem cells, and induced endothelial cells at a set ratio, the cells self-condensed into three-dimensional nephrogenic progenitor cells which we refer to as 3D-NPCs. Immunofluorescence-based stainings of sectioned 3D-NPCs revealed cells expressing the renal progenitor cell markers (SIX2 and PAX8), podocyte markers (Nephrin and Podocin), the endothelial marker (CD31), and mesenchymal markers (Vimentin and PDGFR-β). These 3D-NPCs share kidney progenitor characteristics and thus the potential to differentiate into podocytes and proximal and distal tubules. As urine-derived renal progenitor cells can be easily obtained from cells shed into urine, the generation of 3D-NPCs directly from renal progenitor cells instead of pluripotent stem cells or kidney biopsies holds a great potential for the use in nephrotoxicity tests, drug screening, modelling nephrogenesis and diseases.

Background: Activated parietal epithelial cells (PECs) and podocytes are key effector cells in the development of crescentic glomerulonephritis and focal segmental glomerulosclerosis (FSGS). Platelet-derived growth factor (PDGF)-C has been found to be important for tubulointerstitial fibrosis development, but its relevance for crescentic glomerulonephritis and FSGS was previously unknown. Methods: To address this, expression analyses for both PDGF-C and its receptor PDGFRα were carried out in mouse and human kidney tissues. To further elucidate a functional role of PDGF-C, the murine nephrotoxic nephritis model of crescentic glomerulonephritis was induced in a) Pdgfc -deficient mice, b) mice treated with a neutralizing PDGF-C antibody, and c) Pax8-cre::Pdgfc ^fl / ^fl mice with conditional Pdgfc deletion in kidney epithelial cells. We also subjected the collapsing FSGS model of the anti-Thy1.1 transgenic mouse to pharmacological PDGF-C inhibition. The studies were supplemented by PEC in vitro analyses. Results: Our data showed that PDGF-C was upregulated in PECs and expressed de novo in podocytes under disease conditions. It promoted the proliferation and activation of primary as well as conditionally immortalized PECs in vitro . In both the genetic and pharmacological PDGF-C intervention studies in murine crescentic glomerulonephritis and FSGS, significant improvements in glomerular crescent formation, glomerular sclerosis, renal inflammation and kidney function parameters were observed upon PDGF-C deficiency or antagonism. Mechanistically, transcription factor FOXM1 was identified as a mediator of disease-related PDGF-C expression in PECs. Conclusions: Our studies identified epithelial PDGF-C as a contributor to disease progression in crescentic glomerulonephritis and FSGS, acting in part through the activation of parietal epithelial cells.