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Mukherjee E, Maringer K, Papke E, Bushnell D, Schaefer C, Kramann R, Ho J, Humphreys BD, Bates C, Sims-Lucas S. Endothelial marker-expressing stromal cells are critical for kidney formation. Am J Physiol Renal Physiol 2017; 313:F611-F620. [PMID: 28539333 PMCID: PMC6148306 DOI: 10.1152/ajprenal.00136.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 05/05/2017] [Accepted: 05/22/2017] [Indexed: 11/22/2022] Open
Abstract
Kidneys are highly vascularized and contain many distinct vascular beds. However, the origins of renal endothelial cells and roles of the developing endothelia in the formation of the kidney are unclear. We have shown that the Foxd1-positive renal stroma gives rise to endothelial marker-expressing progenitors that are incorporated within a subset of peritubular capillaries; however, the significance of these cells is unclear. The purpose of this study was to determine whether deletion of Flk1 in the Foxd1 stroma was important for renal development. To that end, we conditionally deleted Flk1 (critical for endothelial cell development) in the renal stroma by breeding-floxed Flk1 mice (Flk1fl/fl ) with Foxd1cre mice to generate Foxd1cre; Flk1fl/fl (Flk1ST-/- ) mice. We then performed FACsorting, histological, morphometric, and metabolic analyses of Flk1ST-/- vs. control mice. We confirmed decreased expression of endothelial markers in the renal stroma of Flk1ST-/- kidneys via flow sorting and immunostaining, and upon interrogation of embryonic and postnatal Flk1ST-/- mice, we found they had dilated peritubular capillaries. Three-dimensional reconstructions showed reduced ureteric branching and fewer nephrons in developing Flk1ST-/- kidneys vs. CONTROLS Juvenile Flk1ST-/- kidneys displayed renal papillary hypoplasia and a paucity of collecting ducts. Twenty-four-hour urine collections revealed that postnatal Flk1ST-/- mice had urinary-concentrating defects. Thus, while lineage-tracing revealed that the renal cortical stroma gave rise to a small subset of endothelial progenitors, these Flk1-expressing stromal cells are critical for patterning the peritubular capillaries. Also, loss of Flk1 in the renal stroma leads to nonautonomous-patterning defects in ureteric lineages.
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Affiliation(s)
- Elina Mukherjee
- Rangos Research Center, Children's Hospital of Pittsburgh of University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Katherine Maringer
- Rangos Research Center, Children's Hospital of Pittsburgh of University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Emily Papke
- Rangos Research Center, Children's Hospital of Pittsburgh of University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Daniel Bushnell
- Rangos Research Center, Children's Hospital of Pittsburgh of University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Caitlin Schaefer
- Rangos Research Center, Children's Hospital of Pittsburgh of University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Rafael Kramann
- Division of Nephrology and Clinical Immunology, Rheinisch-Westfälische Technische Hochschule, Aachen University, Aachen, Germany
| | - Jacqueline Ho
- Rangos Research Center, Children's Hospital of Pittsburgh of University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Benjamin D Humphreys
- Renal Division, Washington University School of Medicine, St. Louis, Missouri; and
| | - Carlton Bates
- Rangos Research Center, Children's Hospital of Pittsburgh of University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Sunder Sims-Lucas
- Rangos Research Center, Children's Hospital of Pittsburgh of University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania;
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, Pennsylvania
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Maringer K, Sims-Lucas S. The multifaceted role of the renal microvasculature during acute kidney injury. Pediatr Nephrol 2016; 31:1231-40. [PMID: 26493067 PMCID: PMC4841763 DOI: 10.1007/s00467-015-3231-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 09/28/2015] [Accepted: 09/29/2015] [Indexed: 12/20/2022]
Abstract
Pediatric acute kidney injury (AKI) represents a complex disease process for clinicians as it is multifactorial in cause and only limited treatment or preventatives are available. The renal microvasculature has recently been implicated in AKI as a strong therapeutic candidate involved in both injury and recovery. Significant progress has been made in the ability to study the renal microvasculature following ischemic AKI and its role in repair. Advances have also been made in elucidating cell-cell interactions and the molecular mechanisms involved in these interactions. The ability of the kidney to repair post AKI is closely linked to alterations in hypoxia, and these studies are elucidated in this review. Injury to the microvasculature following AKI plays an integral role in mediating the inflammatory response, thereby complicating potential therapeutics. However, recent work with experimental animal models suggests that the endothelium and its cellular and molecular interactions are attractive targets to prevent injury or hasten repair following AKI. Here, we review the cellular and molecular mechanisms of the renal endothelium in AKI, as well as repair and recovery, and potential therapeutics to prevent or ameliorate injury and hasten repair.
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Affiliation(s)
- Katherine Maringer
- Rangos Research Center, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA, USA
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Sunder Sims-Lucas
- Rangos Research Center, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA, USA.
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
- Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA, USA.
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Ensuring the Quality of Stem Cell-Derived In Vitro Models for Toxicity Testing. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 856:259-297. [DOI: 10.1007/978-3-319-33826-2_11] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Hum S, Rymer C, Schaefer C, Bushnell D, Sims-Lucas S. Ablation of the renal stroma defines its critical role in nephron progenitor and vasculature patterning. PLoS One 2014; 9:e88400. [PMID: 24505489 PMCID: PMC3914987 DOI: 10.1371/journal.pone.0088400] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 01/05/2014] [Indexed: 12/03/2022] Open
Abstract
The renal stroma is an embryonic cell population located in the cortex that provides a structural framework as well as a source of endothelial progenitors for the developing kidney. The exact role of the renal stroma in normal kidney development hasn't been clearly defined. However, previous studies have shown that the genetic deletion of Foxd1, a renal stroma specific gene, leads to severe kidney malformations confirming the importance of stroma in normal kidney development. This study further investigates the role of renal stroma by ablating Foxd1-derived stroma cells themselves and observing the response of the remaining cell populations. A Foxd1cre (renal stroma specific) mouse was crossed with a diphtheria toxin mouse (DTA) to specifically induce apoptosis in stromal cells. Histological examination of kidneys at embryonic day 13.5–18.5 showed a lack of stromal tissue, mispatterning of renal structures, and dysplastic and/or fused horseshoe kidneys. Immunofluorescence staining of nephron progenitors, vasculature, ureteric epithelium, differentiated nephron progenitors, and vascular supportive cells revealed that mutants had thickened nephron progenitor caps, cortical regions devoid of nephron progenitors, aberrant vessel patterning and thickening, ureteric branching defects and migration of differentiated nephron structures into the medulla. The similarities between the renal deformities caused by Foxd1 genetic knockout and Foxd1DTA mouse models reveal the importance of Foxd1 in mediating and maintaining the functional integrity of the renal stroma.
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Affiliation(s)
- Stephanie Hum
- Rangos Research Center, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Christopher Rymer
- Rangos Research Center, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Caitlin Schaefer
- Rangos Research Center, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Daniel Bushnell
- Rangos Research Center, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Sunder Sims-Lucas
- Rangos Research Center, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- * E-mail:
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Nogueira-Silva C, Piairo P, Carvalho-Dias E, Peixoto FO, Moura RS, Correia-Pinto J. Leukemia inhibitory factor in rat fetal lung development: expression and functional studies. PLoS One 2012; 7:e30517. [PMID: 22291973 PMCID: PMC3264589 DOI: 10.1371/journal.pone.0030517] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Accepted: 12/16/2011] [Indexed: 11/29/2022] Open
Abstract
Background Leukemia inhibitory factor (LIF) and interleukin-6 (IL-6) are members of the family of the glycoprotein 130 (gp130)-type cytokines. These cytokines share gp130 as a common signal transducer, which explains why they show some functional redundancy. Recently, it was demonstrated that IL-6 promotes fetal lung branching. Additionally, LIF has been implicated in developmental processes of some branching organs. Thus, in this study LIF expression pattern and its effects on fetal rat lung morphogenesis were assessed. Methodology/Principal Findings LIF and its subunit receptor LIFRα expression levels were evaluated by immunohistochemistry and western blot in fetal rat lungs of different gestational ages, ranging from 13.5 to 21.5 days post-conception. Throughout all gestational ages studied, LIF was constitutively expressed in pulmonary epithelium, whereas LIFRα was first mainly expressed in the mesenchyme, but after pseudoglandular stage it was also observed in epithelial cells. These results point to a LIF epithelium-mesenchyme cross-talk, which is known to be important for lung branching process. Regarding functional studies, fetal lung explants were cultured with increasing doses of LIF or LIF neutralizing antibodies during 4 days. MAPK, AKT, and STAT3 phosphorylation in the treated lung explants was analyzed. LIF supplementation significantly inhibited lung growth in spite of an increase in p44/42 phosphorylation. On the other hand, LIF inhibition significantly stimulated lung growth via p38 and Akt pathways. Conclusions/Significance The present study describes that LIF and its subunit receptor LIFRα are constitutively expressed during fetal lung development and that they have an inhibitory physiological role on fetal lung branching.
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Affiliation(s)
- Cristina Nogueira-Silva
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3Bs - PT Government Associate Laboratory, Braga/Guimarães, Portugal
- Department of Obstetrics and Gynecology, Hospital de Braga, Braga, Portugal
| | - Paulina Piairo
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3Bs - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Emanuel Carvalho-Dias
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3Bs - PT Government Associate Laboratory, Braga/Guimarães, Portugal
- Department of Urology, Hospital de São João, Porto, Portugal
| | - Francisca O. Peixoto
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3Bs - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Rute S. Moura
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3Bs - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Jorge Correia-Pinto
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3Bs - PT Government Associate Laboratory, Braga/Guimarães, Portugal
- Department of Pediatric Surgery, Hospital de Braga, Braga, Portugal
- * E-mail:
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Rosines E, Johkura K, Zhang X, Schmidt HJ, Decambre M, Bush KT, Nigam SK. Constructing kidney-like tissues from cells based on programs for organ development: toward a method of in vitro tissue engineering of the kidney. Tissue Eng Part A 2011; 16:2441-55. [PMID: 20214453 DOI: 10.1089/ten.tea.2009.0548] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The plausibility of constructing vascularized three-dimensional (3D) kidney tissue from cells was investigated. The kidney develops from mutual inductive interactions between cells of the ureteric bud (UB), derived from the Wolffian duct (WD), and the metanephric mesenchyme (MM). We found that isolated MMs were capable of inducing branching morphogenesis of the WD (an epithelial tube) in recombination cultures; suggesting that the isolated MM retains inductive capacity for WD-derived epithelial tubule cells other than those from the UB. Hanging drop aggregates of embryonic and adult renal epithelial cells from UB and mouse inner medullary collecting duct cell (IMCD) lines, which are ultimately of WD origin, were capable of inducing MM epithelialization and tubulogenesis with apparent connections (UB cells) and collecting duct-like tubules with lumens (IMCD). This supports the view that the collecting system can be constructed from certain epithelial cells (those ultimately of WD origin) when stimulated by MM. Although the functions of the MM could not be replaced by cultured mesenchymal cells, primary MM cells and one MM-derived cell line (BSN) produced factors that stimulate UB branching morphogenesis, whereas another, rat inducible metanephric mesenchyme (RIMM-18), supported WD budding as a feeder layer. This indicates that some MM functions can be recapitulated by cells. Although engineering of a kidney-like tissue from cultured cells alone remains to be achieved, these results suggest the feasibility of such an approach following the normal developmental progression of the UB and MM. Consistent with this notion, implants of kidney-like tissues constructed in vitro from recombinations of the UB and MM survived for over 5 weeks and achieved an apparently host-derived glomerular vasculature. Lastly, we addressed the issue of optimal macro- and micro-patterning of kidney-like tissue, which might be necessary for function of an organ assembled using a tissue engineering approach. To identify suitable conditions, 3D reconstructions of HoxB7-green fluorescent protein mouse rudiments (E12) cultured on a filter or suspended in a collagen gel (type I or type IV) revealed that type IV collagen 3D culture supports the deepest tissue growth (600 +/- 8 microm) and the largest kidney volume (0.22 +/- 0.02 mm(3)), and enabled the development of an umbrella-shaped collecting system such as occurs in vivo. Taken together with prior work (Rosines et al., 2007; Steer et al., 2002), these results support the plausibility of a developmental strategy for constructing and propagating vascularized 3D kidney-like tissues from recombinations of cultured renal progenitor cells and/or primordial tissue.
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Affiliation(s)
- Eran Rosines
- Department of Bioengineering, University of California , San Diego, La Jolla, California, USA
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Lee SJ, Cho SJ, Ju SY, Ryu KH, Sung SH, Park EA. Effect of retinoic acid on renal development in newborn mice treated with an angiogenesis inhibitor. Pediatr Int 2010; 52:386-92. [PMID: 19761519 DOI: 10.1111/j.1442-200x.2009.02959.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND A mouse model of impaired renal development was developed and the effect of retinoic acid (RA) was investigated in this animal model. METHODS An angiogenesis inhibitor (SU1498) was injected s.c. into day 3 C57BL/6 newborn mice to create a model of arrested renal development. RA (2 mg/kg) was injected i.p. for 10 days. Morphometry and immunohistochemistry were done. RESULTS Mice injected with SU1498 demonstrated deranged renal development in tubular structure and glomerular tuft area. Cortical thickness and area of glomerular tuft were significantly decreased after vascular endothelial growth factor (VEGF) inhibitor, and were significantly restored by RA. The length of capillary loops/glomerulus, the number of podocytes/glomerulus, and density of peritubular capillaries on CD31 immunostaining were significantly decreased by VEGF blocking and recovered by RA. CONCLUSIONS VEGF plays a major role in renal development, and RA reverses the inhibited development caused by an angiogenesis inhibitor.
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Affiliation(s)
- Soo Jeong Lee
- Department of Pediatrics, Ewha Womans University School of Medicine, Seoul, Republic of Korea
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Miess C, Glashauser A, Denk L, deVries U, Minuth WW. The interface between generating renal tubules and a polyester fleece in comparison to the interstitium of the developing kidney. Ann Biomed Eng 2010; 38:2197-209. [PMID: 20309733 DOI: 10.1007/s10439-010-0006-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Accepted: 03/09/2010] [Indexed: 01/08/2023]
Abstract
An increasing number of investigations is dealing with the repair of acute and chronic renal failure by the application of stem/progenitor cells. However, accurate data concerning the cell biological mechanisms controlling the process of regeneration are scarce. For that reason new implantation techniques, advanced biomaterials and morphogens supporting regeneration of renal parenchyma are under research. Special focus is directed to structural and functional features of the interface between generating tubules and the surrounding interstitial space. The aim of the present experiments was to investigate structural features of the interstitium during generation of tubules. Stem/progenitor cells were isolated from neonatal rabbit kidney and mounted between layers of a polyester fleece to create an artificial interstitium. Perfusion culture was performed for 13 days in chemically defined Iscove's Modified Dulbecco's Medium containing aldosterone (1 x 10(-7) M) as tubulogenic factor. Recordings of the artificial interstitium in comparison to the developing kidney were performed by morphometric analysis, scanning and transmission electron microscopy. The degree of differentiation was registered by immunohistochemistry. The data reveal that generated tubules are embedded in a complex network of fibers consisting of newly synthesized extracellular matrix proteins. Morphometric analysis further shows that the majority of tubules within the artificial interstitium develops in a surprisingly close distance between 5 and 25 mum to each other. The abundance of synthesized extracellular matrix acts obviously as a spacer keeping generated tubules in distance. For comparison, the same principle of construction is found in the developing parenchyma of the neonatal kidney. Most astonishingly, scanning electron microscopy reveals that the composition of interstitial matrix is not homogeneous but differs along a cortico-medullary axis of proceeding tubule development.
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Affiliation(s)
- C Miess
- Department of Molecular and Cellular Anatomy, University of Regensburg, University Street 31, D-93053 Regensburg, Germany
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The tubulogenic effect of aldosterone is attributed to intact binding and intracellular response of the mineralocorticoid receptor. Open Life Sci 2007. [DOI: 10.2478/s11535-007-0030-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
AbstractLittle is known about the extra- and intracellular stimuli inducing renal stem/progenitor cells to develop into three-dimensionally structured tubules. To study this specific development in a controlled environment, we used an advanced culture technique. Embryonic tissue derived from neonatal rabbit kidney was placed in a perfusion culture container at the interface of an artificial interstitium made of a polyester fleece. Culture was carried out in chemically defined Iscove’s Modified Dulbecco’s Medium (IMDM) for 13 days. Development of tubules was histochemically detected on cryosections labeled with Soybean Agglutinin (SBA). The experiments showed that aldosterone exerts a specific tubulogenic effect. Application of aldosterone (1 × 10−7 M) raised numerous SBA-labeled tubules, while in the absence of the steroid hormone the development of tubules was lacking. Specificity of hormone action was analyzed by the use of aldosterone antagonists. Administration of spironolactone (1 × 10−4 M) and canrenoate (1 × 10−5 M) completely inhibited the development of tubules. Finally, disrupting the intracellular molecular complex of the mineralocorticoid receptor (MR) and heat shock proteins by geldanamycin (2 μg/ml) prevented the development of tubules. Our results suggest that the tubulogenic effect induced by aldosterone is attributed to both hormone binding and an undisturbed intracellular response of the MR.
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Levinson R, Mendelsohn C. Stromal progenitors are important for patterning epithelial and mesenchymal cell types in the embryonic kidney. Semin Cell Dev Biol 2003; 14:225-31. [PMID: 14627121 DOI: 10.1016/s1084-9521(03)00025-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Growth and expansion of the embryonic kidney is driven in large part by continuous branching morphogenesis and nephron induction that occurs in a restricted domain beneath the renal capsule called the nephrogenic zone. Here, new ureteric bud branches and nephron aggregates form surrounded by a layer of cortical stromal cell progenitors. The boundaries and inductive activities of the nephrogenic zone are maintained as the kidney grows. As new ureteric bud branches and nephrogenic aggregates form, older generations of ureteric bud branches, renal vesicles and stromal progenitors are displaced from the nephrogenic zone and undergo further differentiation surrounded by medullary stroma, a different population of stromal cells. Recent studies suggest that cortical and medullary stromal progenitors may be an important source of signals that maintain outer and inner zones of differentiation in the embryonic kidney, and regulate distinct events important for differentiation of nephrons and the collecting duct system.
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Affiliation(s)
- Randy Levinson
- Department of Urology, Columbia University, 650 West 168th Street, New York, NY 10032, USA
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