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Seaayfan E, Nasrah S, Quell L, Radi A, Kleim M, Schermuly RT, Weber S, Laghmani K, Kömhoff M. Reciprocal Regulation of MAGED2 and HIF-1α Augments Their Expression under Hypoxia: Role of cAMP and PKA Type II. Cells 2022; 11:3424. [PMID: 36359819 PMCID: PMC9655371 DOI: 10.3390/cells11213424] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 10/26/2022] [Accepted: 10/26/2022] [Indexed: 09/10/2023] Open
Abstract
Hypoxia stabilizes the transcription factor HIF-1α, which promotes the transcription of many genes essential to adapt to reduced oxygen levels. Besides proline hydroxylation, expression of HIF-1α is also regulated by a range of other posttranslational modifications including phosphorylation by cAMP-dependent protein kinase A (PKA), which stabilizes HIF-1α. We recently demonstrated that MAGED2 is required for cAMP generation under hypoxia and proposed that this regulation may explain the transient nature of antenatal Bartter syndrome (aBS) due to MAGED2 mutations. Consequently, we sought to determine whether hypoxic induction of HIF-1α requires also MAGED2. In HEK293 and HeLa cells, MAGED2 knock-down impaired maximal induction of HIF-1α under physical hypoxia as evidenced by time-course experiments, which showed a signification reduction of HIF-1α upon MAGED2 depletion. Similarly, using cobalt chloride to induce HIF-1α, MAGED2 depletion impaired its appropriate induction. Given the known effect of the cAMP/PKA pathway on the hypoxic induction of HIF-1α, we sought to rescue impaired HIF-1α induction with isoproterenol and forskolin acting upstream and downstream of Gαs, respectively. Importantly, while forskolin induced HIF-1α above control levels in MAGED2-depleted cells, isoproterenol had no effect. To further delineate which PKA subtype is involved, we analyzed the effect of two PKA inhibitors and identified that PKA type II regulates HIF-1α. Interestingly, MAGED2 mRNA and protein were also increased under hypoxia by a cAMP mimetic. Moreover, MAGED2 protein expression also required HIF-1α. Thus, our data provide evidence for reciprocal regulation of MAGED2 and HIF-1α under hypoxia, revealing therefore a new regulatory mechanism that may further explain the transient nature of aBS caused by MAGED2 mutations.
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Affiliation(s)
- Elie Seaayfan
- University Children’s Hospital, Philipps University, 35043 Marburg, Germany
| | - Sadiq Nasrah
- University Children’s Hospital, Philipps University, 35043 Marburg, Germany
| | - Lea Quell
- University Children’s Hospital, Philipps University, 35043 Marburg, Germany
| | - Aline Radi
- University Children’s Hospital, Philipps University, 35043 Marburg, Germany
| | - Maja Kleim
- University Children’s Hospital, Philipps University, 35043 Marburg, Germany
| | - Ralph T. Schermuly
- Department of Internal Medicine, Member of the German Center for Lung Research (DZL), Excellence Cluster Cardio-Pulmonary Institute (CPI), Justus-Liebig-University, 35392 Giessen, Germany
| | - Stefanie Weber
- University Children’s Hospital, Philipps University, 35043 Marburg, Germany
| | - Kamel Laghmani
- Centre de Recherche des Cordeliers, Sorbonne Université, Inserm, Université de Paris, CNRS, ERL8228, F-75006 Paris, France
| | - Martin Kömhoff
- University Children’s Hospital, Philipps University, 35043 Marburg, Germany
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2
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Koning M, Dumas SJ, Avramut MC, Koning RI, Meta E, Lievers E, Wiersma LE, Borri M, Liang X, Xie L, Liu P, Chen F, Lin L, Luo Y, Mulder J, Spijker HS, Jaffredo T, van den Berg BM, Carmeliet P, van den Berg CW, Rabelink TJ. Vasculogenesis in kidney organoids upon transplantation. NPJ Regen Med 2022; 7:40. [DOI: 10.1038/s41536-022-00237-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 07/20/2022] [Indexed: 02/07/2023] Open
Abstract
AbstractHuman induced pluripotent stem cell-derived kidney organoids have potential for disease modeling and to be developed into clinically transplantable auxiliary tissue. However, they lack a functional vasculature, and the sparse endogenous endothelial cells (ECs) are lost upon prolonged culture in vitro, limiting maturation and applicability. Here, we use intracoelomic transplantation in chicken embryos followed by single-cell RNA sequencing and advanced imaging platforms to induce and study vasculogenesis in kidney organoids. We show expansion of human organoid-derived ECs that reorganize into perfused capillaries and form a chimeric vascular network with host-derived blood vessels. Ligand-receptor analysis infers extensive potential interactions of human ECs with perivascular cells upon transplantation, enabling vessel wall stabilization. Perfused glomeruli display maturation and morphogenesis to capillary loop stage. Our findings demonstrate the beneficial effect of vascularization on not only epithelial cell types, but also the mesenchymal compartment, inducing the expansion of ´on target´ perivascular stromal cells, which in turn are required for further maturation and stabilization of the neo-vasculature. The here described vasculogenic capacity of kidney organoids will have to be deployed to achieve meaningful glomerular maturation and kidney morphogenesis in vitro.
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MAGED2 Is Required under Hypoxia for cAMP Signaling by Inhibiting MDM2-Dependent Endocytosis of G-Alpha-S. Cells 2022; 11:cells11162546. [PMID: 36010623 PMCID: PMC9406315 DOI: 10.3390/cells11162546] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 08/14/2022] [Accepted: 08/15/2022] [Indexed: 01/15/2023] Open
Abstract
Mutations in MAGED2 cause transient Bartter syndrome characterized by severe renal salt wasting in fetuses and infants, which leads to massive polyhydramnios causing preterm labor, extreme prematurity and perinatal death. Notably, this condition resolves spontaneously in parallel with developmental increase in renal oxygenation. MAGED2 interacts with G-alpha-S (Gαs). Given the role of Gαs in activating adenylyl cyclase at the plasma membrane and consequently generating cAMP to promote renal salt reabsorption via protein kinase A (PKA), we hypothesized that MAGED2 is required for this signaling pathway under hypoxic conditions such as in fetuses. Consistent with that, under both physical and chemical hypoxia, knockdown of MAGED2 in renal (HEK293) and cancer (HeLa) cell culture models caused internalization of Gαs, which was fully reversible upon reoxygenation. In contrast to Gαs, cell surface expression of the β2-adrenergic receptor, which is coupled to Gαs, was not affected by MAGED2 depletion, demonstrating specific regulation of Gαs by MAGED2. Importantly, the internalization of Gαs due to MAGED2 deficiency significantly reduced cAMP generation and PKA activity. Interestingly, the internalization of Gαs was blocked by preventing its endocytosis with dynasore. Given the role of E3 ubiquitin ligases, which can be regulated by MAGE-proteins, in regulating endocytosis, we assessed the potential role of MDM2-dependent ubiquitination in MAGED2 deficiency-induced internalization of Gαs under hypoxia. Remarkably, MDM2 depletion or its chemical inhibition fully abolished Gαs-endocytosis following MAGED2 knockdown. Moreover, endocytosis of Gαs was also blocked by mutation of ubiquitin acceptor sites in Gαs. Thus, we reveal that MAGED2 is essential for the cAMP/PKA pathway under hypoxia to specifically regulate Gαs endocytosis by blocking MDM2-dependent ubiquitination of Gαs. This may explain, at least in part, the transient nature of Bartter syndrome caused by MAGED2 mutations and opens new avenues for therapy in these patients.
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4
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Schumacher A, Roumans N, Rademakers T, Joris V, Eischen-Loges MJ, van Griensven M, LaPointe VL. Enhanced Microvasculature Formation and Patterning in iPSC–Derived Kidney Organoids Cultured in Physiological Hypoxia. Front Bioeng Biotechnol 2022; 10:860138. [PMID: 35782512 PMCID: PMC9240933 DOI: 10.3389/fbioe.2022.860138] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Accepted: 05/05/2022] [Indexed: 01/10/2023] Open
Abstract
Stem cell–derived kidney organoids have been shown to self-organize from induced pluripotent stem cells into most important renal structures. However, the structures remain immature in culture and contain endothelial networks with low connectivity and limited organoid invasion. Furthermore, the nephrons lose their phenotype after approximately 25 days. To become applicable for future transplantation, further maturation in vitro is essential. Since kidneys in vivo develop in hypoxia, we studied the modulation of oxygen availability in culture. We hypothesized that introducing long-term culture at physiological hypoxia, rather than the normally applied non-physiological, hyperoxic 21% O2, could initiate angiogenesis, lead to enhanced growth factor expression and improve the endothelial patterning. We therefore cultured the kidney organoids at 7% O2 instead of 21% O2 for up to 25 days and evaluated nephrogenesis, growth factor expression such as VEGF-A and vascularization. Whole mount imaging revealed a homogenous morphology of the endothelial network with enhanced sprouting and interconnectivity when the kidney organoids were cultured in hypoxia. Three-dimensional vessel quantification confirmed that the hypoxic culture led to an increased average vessel length, likely due to the observed upregulation of VEGFA-189 and VEGFA-121, and downregulation of the antiangiogenic protein VEGF-A165b measured in hypoxia. This research indicates the importance of optimization of oxygen availability in organoid systems and the potential of hypoxic culture conditions in improving the vascularization of organoids.
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Affiliation(s)
- Anika Schumacher
- Department of Cell Biology–Inspired Tissue Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Maastricht, Netherlands
| | - Nadia Roumans
- Department of Cell Biology–Inspired Tissue Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Maastricht, Netherlands
| | - Timo Rademakers
- Department of Cell Biology–Inspired Tissue Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Maastricht, Netherlands
| | - Virginie Joris
- Department of Cell Biology–Inspired Tissue Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Maastricht, Netherlands
| | - Maria José Eischen-Loges
- Department of Cell Biology–Inspired Tissue Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Maastricht, Netherlands
- Department of Instructive Biomaterials Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Maastricht, Netherlands
| | - Martijn van Griensven
- Department of Cell Biology–Inspired Tissue Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Maastricht, Netherlands
| | - Vanessa L.S. LaPointe
- Department of Cell Biology–Inspired Tissue Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Maastricht, Netherlands
- *Correspondence: Vanessa L.S. LaPointe,
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Xiaoshi J, Maoquan L, Jiwei W, Jinqiu N, Ke Z. SETD7 mediates the vascular invasion in articular cartilage and chondrocytes apoptosis in osteoarthriis. FASEB J 2021; 35:e21283. [PMID: 33617050 DOI: 10.1096/fj.202000373rrrr] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 11/26/2020] [Accepted: 12/01/2020] [Indexed: 12/23/2022]
Abstract
The pathological characteristics of osteoarthritis are cartilage matrix degradation, chondrocytes apoptosis, and low-grade inflammation of the joint. Recent studies have shown that blood vessels grow from the subchondral bone to the articular cartilage. However, the relationship among inflammation, angiogenesis, and chondrocyte apoptosis is still unclear. We found that chondrocytes could secrete chemokines and VEGF to promote the migration of vascular endothelial cells in response to TNF-α stimulation. The invasion of blood vessels leads to increased oxygen tension in the local environment, which increased the expression of SETD7 in chondrocytes by activating the JAK-STAT5 pathway. The bond of phosphorylated STAT5 and the specific locus in the promoter of SETD7 directly increased the transcription of SETD7. On the one hand, SETD7-regulated chemokine expression by forming a positive loop; on the other hand, SETD7-mediated chondrocyte apoptosis by inhibiting the nuclear localization of HIF-1α. In this study, we discovered a novel function of chondrocytes as mediators of inflammation and angiogenesis. Our study demonstrates that SETD7 is a potential molecular target to prevent OA development and progression.
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Affiliation(s)
- Jia Xiaoshi
- Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China.,Guangdong Engineering Research Center of Technology and Materials for Oral Reconstruction, Guangzhou, China
| | - Li Maoquan
- Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China.,Guangdong Engineering Research Center of Technology and Materials for Oral Reconstruction, Guangzhou, China
| | - Wang Jiwei
- Key Laboratory of Oral Medicine, Guangzhou Institute of Oral Disease, Stomatology Hospital of Guangzhou Medical University, Guangzhou, China
| | - Ning Jinqiu
- Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China.,Guangdong Engineering Research Center of Technology and Materials for Oral Reconstruction, Guangzhou, China
| | - Zhao Ke
- Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China.,Guangdong Engineering Research Center of Technology and Materials for Oral Reconstruction, Guangzhou, China
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6
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Parvin N, Charlton JR, Baldelomar EJ, Derakhshan JJ, Bennett KM. Mapping vascular and glomerular pathology in a rabbit model of neonatal acute kidney injury using MRI. Anat Rec (Hoboken) 2020; 303:2716-2728. [PMID: 32445514 PMCID: PMC7680718 DOI: 10.1002/ar.24419] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 01/30/2020] [Accepted: 03/03/2020] [Indexed: 12/27/2022]
Abstract
Acute kidney injury (AKI) in premature neonates is common due to the administration of life-saving therapies. The impact of AKI on renal morphology and susceptibility to further renal damage is poorly understood. Recent advances in radiological imaging have allowed integration of soft tissue morphology in the intact organ, facilitating a more complete understanding of changes in tissue microstructure associated with pathology. Here, we applied magnetic resonance imaging (MRI) to detect both glomerular and vascular changes in a rabbit model of neonatal AKI, induced by indomethacin and gentamicin. Using combined spin-echo MRI and cationic ferritin enhanced gradient-echo MRI (CFE-MRI), we observed (a) an increased cortical arterial diameter in the AKI cohort compared to healthy controls, and (b) focal loss of vascular density and glomerular loss in a circumferential band ~1 mm from the cortical surface. This combined use of vascular and glomerular imaging may give insight into the etiology of AKI and its impact on renal health later in life.
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Affiliation(s)
- Neda Parvin
- Department of Radiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Jennifer R Charlton
- University of Virginia Children's Hospital, Department of Pediatrics, Charlottesville, Virginia, USA
| | - Edwin J Baldelomar
- Department of Radiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Jamal J Derakhshan
- Department of Radiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Kevin M Bennett
- Department of Radiology, Washington University in St. Louis, St. Louis, Missouri, USA
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7
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Ma T, Yang Y, Quan X, Lu L, Xia B, Gao J, Qi F, Li S, Zhao L, Mei L, Zheng Y, Shen Y, Luo Z, Jin Y, Huang J. Oxygen carrier in core-shell fibers synthesized by coaxial electrospinning enhances Schwann cell survival and nerve regeneration. Am J Cancer Res 2020; 10:8957-8973. [PMID: 32802174 PMCID: PMC7415813 DOI: 10.7150/thno.45035] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 06/17/2020] [Indexed: 12/11/2022] Open
Abstract
Rationale: Local hypoxia is a challenge for fabrication of cellular grafts and treatment of peripheral nerve injury. In our previous studies, we demonstrated that perfluorotributylamine (PFTBA) could provide short term oxygen supply to Schwann cells (SCs) and counteract the detrimental effects of hypoxia on SCs during the early stages of nerve injury. However, the quick release of oxygen in PFTBA compromised its ability to counteract hypoxia over an extended time, limiting its performance in peripheral nerve injury. Methods: In this study, PFTBA-based oxygen carrier systems were prepared through coaxial electrospinning to prolong the time course of oxygen release. Core-shell structures were fabricated, optimized, and the oxygen kinetics of PFTBA-enriched core-shell fibers evaluated. The effect of core-shells on the survival and function of SCs was examined in both 2D and 3D systems as well as in vivo. The system was used to bridge large sciatic nerve defects in rats. Results: PFTBA core-shell fibers provided high levels of oxygen to SCs in vitro, enhancing their survival, and increasing NGF, BDNF, and VEGF expression in 2D and 3D culture systems under hypoxic condition. In vivo analysis showed that the majority of GFP-expressing SCs in the PFTBA conduit remained viable 14 days post-implantation. We found that axons in PFTBA oxygen carrier scaffold improved axonal regeneration, remyelination, and recovery. Conclusion: A synthetic oxygen carrier in core-shell fibers was fabricated by the coaxial electrospinning technique and was capable of enhancing SC survival and nerve regeneration by prolonged oxygen supply. These findings provide a new strategy for fabricating cellular scaffolds to achieve regeneration in peripheral nerve injury treatment and other aerobic tissue injuries.
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8
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Cargill KR, Chiba T, Murali A, Mukherjee E, Crinzi E, Sims-Lucas S. Prenatal hypoxia increases susceptibility to kidney injury. PLoS One 2020; 15:e0229618. [PMID: 32084244 PMCID: PMC7034911 DOI: 10.1371/journal.pone.0229618] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 02/10/2020] [Indexed: 12/16/2022] Open
Abstract
Prenatal hypoxia is a gestational stressor that can result in developmental abnormalities or physiological reprogramming, and often decreases cellular capacity against secondary stress. When a developing fetus is exposed to hypoxia, blood flow is preferentially redirected to vital organs including the brain and heart over other organs including the kidney. Hypoxia-induced injury can lead to structural malformations in the kidney; however, even in the absence of structural lesions, hypoxia can physiologically reprogram the kidney leading to decreased function or increased susceptibility to injury. Our investigation in mice reveals that while prenatal hypoxia does not affect normal development of the kidneys, it primes the kidneys to have an increased susceptibility to kidney injury later in life. We found that our model does not develop structural abnormalities when prenatally exposed to modest 12% O2 as evident by normal histological characterization and gene expression analysis. Further, adult renal structure and function is comparable to mice exposed to ambient oxygen throughout nephrogenesis. However, after induction of kidney injury with a nephrotoxin (cisplatin), the offspring of mice housed in hypoxia exhibit significantly reduced renal function and proximal tubule damage following injury. We conclude that exposure to prenatal hypoxia in utero physiologically reprograms the kidneys leading to increased susceptibility to injury later in life.
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Affiliation(s)
- Kasey R. Cargill
- Department of Pediatrics, Division of Nephrology, UPMC Children’s Hospital of Pittsburgh, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Takuto Chiba
- Department of Pediatrics, Division of Nephrology, UPMC Children’s Hospital of Pittsburgh, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Anjana Murali
- Department of Pediatrics, Division of Nephrology, UPMC Children’s Hospital of Pittsburgh, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Elina Mukherjee
- Department of Pediatrics, Division of Nephrology, UPMC Children’s Hospital of Pittsburgh, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Elizabeth Crinzi
- Department of Pediatrics, Division of Nephrology, UPMC Children’s Hospital of Pittsburgh, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Sunder Sims-Lucas
- Department of Pediatrics, Division of Nephrology, UPMC Children’s Hospital of Pittsburgh, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
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9
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Abstract
Preterm birth is associated with adverse renal health outcomes including hypertension, chronic kidney disease, and an increased rate of progression to end-stage renal failure. This review explores the antenatal, perinatal, and postnatal factors that affect the functional nephron mass of an individual and contribute to long-term kidney outcome. Health-care professionals have opportunities to increase their awareness of the risks to kidney health in this population. Optimizing maternal health around the time of conception and during pregnancy, providing kidney-focused supportive care in the NICU during postnatal nephrogenesis, and avoiding accelerating nephron loss throughout life may all contribute to improved long-term outcomes. There is a need for ongoing research into the long-term kidney outcomes of preterm survivors in mid-to-late adulthood as well as a need for further research into interventions that may improve ex utero nephrogenesis.
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Affiliation(s)
- Amanda Dyson
- Centenary Hospital for Women and Children and Department of Neonatology, Canberra Hospital, Woden, Australia
- Australian National University, Canberra, Australia
| | - Alison L Kent
- University of Rochester and Division of Neonatology, Golisano Children's Hospital at URMC, Rochester, NY
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10
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Cargill K, Hemker SL, Clugston A, Murali A, Mukherjee E, Liu J, Bushnell D, Bodnar AJ, Saifudeen Z, Ho J, Bates CM, Kostka D, Goetzman ES, Sims-Lucas S. Von Hippel-Lindau Acts as a Metabolic Switch Controlling Nephron Progenitor Differentiation. J Am Soc Nephrol 2019; 30:1192-1205. [PMID: 31142573 PMCID: PMC6622426 DOI: 10.1681/asn.2018111170] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Accepted: 04/01/2019] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Nephron progenitors, the cell population that give rise to the functional unit of the kidney, are metabolically active and self-renew under glycolytic conditions. A switch from glycolysis to mitochondrial respiration drives these cells toward differentiation, but the mechanisms that control this switch are poorly defined. Studies have demonstrated that kidney formation is highly dependent on oxygen concentration, which is largely regulated by von Hippel-Lindau (VHL; a protein component of a ubiquitin ligase complex) and hypoxia-inducible factors (a family of transcription factors activated by hypoxia). METHODS To explore VHL as a regulator defining nephron progenitor self-renewal versus differentiation, we bred Six2-TGCtg mice with VHLlox/lox mice to generate mice with a conditional deletion of VHL from Six2+ nephron progenitors. We used histologic, immunofluorescence, RNA sequencing, and metabolic assays to characterize kidneys from these mice and controls during development and up to postnatal day 21. RESULTS By embryonic day 15.5, kidneys of nephron progenitor cell-specific VHL knockout mice begin to exhibit reduced maturation of nephron progenitors. Compared with controls, VHL knockout kidneys are smaller and developmentally delayed by postnatal day 1, and have about half the number of glomeruli at postnatal day 21. VHL knockout nephron progenitors also exhibit persistent Six2 and Wt1 expression, as well as decreased mitochondrial respiration and prolonged reliance on glycolysis. CONCLUSIONS Our findings identify a novel role for VHL in mediating nephron progenitor differentiation through metabolic regulation, and suggest that VHL is required for normal kidney development.
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Affiliation(s)
- Kasey Cargill
- Rangos Research Center, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Shelby L Hemker
- Rangos Research Center, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Andrew Clugston
- Rangos Research Center, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Department of Developmental Biology and
| | - Anjana Murali
- Rangos Research Center, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Elina Mukherjee
- Rangos Research Center, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Jiao Liu
- Section of Pediatric Nephrology, Department of Pediatrics and
- The Hypertension and Renal Centers of Excellence, Tulane University Health Sciences Center, New Orleans, Louisiana
| | - Daniel Bushnell
- Rangos Research Center, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Andrew J Bodnar
- Rangos Research Center, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Zubaida Saifudeen
- Section of Pediatric Nephrology, Department of Pediatrics and
- The Hypertension and Renal Centers of Excellence, Tulane University Health Sciences Center, New Orleans, Louisiana
| | - Jacqueline Ho
- Rangos Research Center, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Carlton M Bates
- Rangos Research Center, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Dennis Kostka
- Rangos Research Center, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Department of Developmental Biology and
| | - Eric S Goetzman
- Rangos Research Center, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Division of Medical Genetics, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Sunder Sims-Lucas
- Rangos Research Center, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania;
- Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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11
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Brinkkoetter PT, Bork T, Salou S, Liang W, Mizi A, Özel C, Koehler S, Hagmann HH, Ising C, Kuczkowski A, Schnyder S, Abed A, Schermer B, Benzing T, Kretz O, Puelles VG, Lagies S, Schlimpert M, Kammerer B, Handschin C, Schell C, Huber TB. Anaerobic Glycolysis Maintains the Glomerular Filtration Barrier Independent of Mitochondrial Metabolism and Dynamics. Cell Rep 2019; 27:1551-1566.e5. [PMID: 31042480 PMCID: PMC6506687 DOI: 10.1016/j.celrep.2019.04.012] [Citation(s) in RCA: 102] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 03/13/2019] [Accepted: 04/02/2019] [Indexed: 12/22/2022] Open
Abstract
The cellular responses induced by mitochondrial dysfunction remain elusive. Intrigued by the lack of almost any glomerular phenotype in patients with profound renal ischemia, we comprehensively investigated the primary sources of energy of glomerular podocytes. Combining functional measurements of oxygen consumption rates, glomerular metabolite analysis, and determination of mitochondrial density of podocytes in vivo, we demonstrate that anaerobic glycolysis and fermentation of glucose to lactate represent the key energy source of podocytes. Under physiological conditions, we could detect neither a developmental nor late-onset pathological phenotype in podocytes with impaired mitochondrial biogenesis machinery, defective mitochondrial fusion-fission apparatus, or reduced mtDNA stability and transcription caused by podocyte-specific deletion of Pgc-1α, Drp1, or Tfam, respectively. Anaerobic glycolysis represents the predominant metabolic pathway of podocytes. These findings offer a strategy to therapeutically interfere with the enhanced podocyte metabolism in various progressive kidney diseases, such as diabetic nephropathy or focal segmental glomerulosclerosis (FSGS).
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Affiliation(s)
- Paul T Brinkkoetter
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Cluster of Excellence on Cellular Stress Responses in Ageing-Associated Diseases (CECAD), Cologne, Germany
| | - Tillmann Bork
- Department of Medicine IV, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Sarah Salou
- Department of Medicine IV, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Wei Liang
- Department of Medicine IV, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Athanasia Mizi
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Cluster of Excellence on Cellular Stress Responses in Ageing-Associated Diseases (CECAD), Cologne, Germany
| | - Cem Özel
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Cluster of Excellence on Cellular Stress Responses in Ageing-Associated Diseases (CECAD), Cologne, Germany
| | - Sybille Koehler
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Cluster of Excellence on Cellular Stress Responses in Ageing-Associated Diseases (CECAD), Cologne, Germany
| | - H Henning Hagmann
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Cluster of Excellence on Cellular Stress Responses in Ageing-Associated Diseases (CECAD), Cologne, Germany
| | - Christina Ising
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Cluster of Excellence on Cellular Stress Responses in Ageing-Associated Diseases (CECAD), Cologne, Germany
| | - Alexander Kuczkowski
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Cluster of Excellence on Cellular Stress Responses in Ageing-Associated Diseases (CECAD), Cologne, Germany
| | | | - Ahmed Abed
- Department of Medicine IV, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Bernhard Schermer
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Cluster of Excellence on Cellular Stress Responses in Ageing-Associated Diseases (CECAD), Cologne, Germany
| | - Thomas Benzing
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Cluster of Excellence on Cellular Stress Responses in Ageing-Associated Diseases (CECAD), Cologne, Germany
| | - Oliver Kretz
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Victor G Puelles
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Division of Nephrology and Clinical Immunology, University Hospital RWTH Aachen, Aachen, Germany; Department of Nephrology, Monash Health, Melbourne, VIC, Australia
| | - Simon Lagies
- Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, Freiburg, Germany; Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Manuel Schlimpert
- Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, Freiburg, Germany; Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Bernd Kammerer
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | | | - Christoph Schell
- Institute of Surgical Pathology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Tobias B Huber
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
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12
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Prenatal hypoxia affected endothelium-dependent vasodilation in mesenteric arteries of aged offspring via increased oxidative stress. Hypertens Res 2019; 42:863-875. [DOI: 10.1038/s41440-018-0181-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Revised: 11/09/2018] [Accepted: 11/14/2018] [Indexed: 12/27/2022]
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13
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Key features of the nephrogenic zone in the fetal human kidney—hardly known but relevant for the detection of first traces impairing nephrogenesis. Cell Tissue Res 2018; 375:589-603. [DOI: 10.1007/s00441-018-2937-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 09/21/2018] [Indexed: 01/09/2023]
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14
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Fathollahipour S, Patil PS, Leipzig ND. Oxygen Regulation in Development: Lessons from Embryogenesis towards Tissue Engineering. Cells Tissues Organs 2018; 205:350-371. [PMID: 30273927 PMCID: PMC6397050 DOI: 10.1159/000493162] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/11/2018] [Indexed: 12/19/2022] Open
Abstract
Oxygen is a vital source of energy necessary to sustain and complete embryonic development. Not only is oxygen the driving force for many cellular functions and metabolism, but it is also involved in regulating stem cell fate, morphogenesis, and organogenesis. Low oxygen levels are the naturally preferred microenvironment for most processes during early development and mainly drive proliferation. Later on, more oxygen and also nutrients are needed for organogenesis and morphogenesis. Therefore, it is critical to maintain oxygen levels within a narrow range as required during development. Modulating oxygen tensions is performed via oxygen homeostasis mainly through the function of hypoxia-inducible factors. Through the function of these factors, oxygen levels are sensed and regulated in different tissues, starting from their embryonic state to adult development. To be able to mimic this process in a tissue engineering setting, it is important to understand the role and levels of oxygen in each developmental stage, from embryonic stem cell differentiation to organogenesis and morphogenesis. Taking lessons from native tissue microenvironments, researchers have explored approaches to control oxygen tensions such as hemoglobin-based, perfluorocarbon-based, and oxygen-generating biomaterials, within synthetic tissue engineering scaffolds and organoids, with the aim of overcoming insufficient or nonuniform oxygen levels and nutrient supply.
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Affiliation(s)
| | - Pritam S Patil
- Department of Chemical and Biomolecular Engineering, University of Akron, Akron, Ohio, USA
| | - Nic D Leipzig
- Department of Chemical and Biomolecular Engineering, University of Akron, Akron, Ohio,
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15
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Fajersztajn L, Veras MM. Hypoxia: From Placental Development to Fetal Programming. Birth Defects Res 2018; 109:1377-1385. [PMID: 29105382 DOI: 10.1002/bdr2.1142] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 09/21/2017] [Indexed: 12/18/2022]
Abstract
Hypoxia may influence normal and different pathological processes. Low oxygenation activates a variety of responses, many of them regulated by hypoxia-inducible factor 1 complex, which is mostly involved in cellular control of O2 consumption and delivery, inhibition of growth and development, and promotion of anaerobic metabolism. Hypoxia plays a significant physiological role in fetal development; it is involved in different embryonic processes, for example, placentation, angiogenesis, and hematopoiesis. More recently, fetal hypoxia has been associated directly or indirectly with fetal programming of heart, brain, and kidney function and metabolism in adulthood. In this review, the role of hypoxia in fetal development, placentation, and fetal programming is summarized. Hypoxia is a basic mechanism involved in different pregnancy disorders and fetal health developmental complications. Although there are scientific data showing that hypoxia mediates changes in the growth trajectory of the fetus, modulates gene expression by epigenetic mechanisms, and determines the health status later in adulthood, more mechanistic studies are needed. Furthermore, if we consider that intrauterine hypoxia is not a rare event, and can be a consequence of unavoidable exposures to air pollution, nutritional deficiencies, obesity, and other very common conditions (drug addiction and stress), the health of future generations may be damaged and the incidence of some diseases will markedly increase as a consequence of disturbed fetal programming. Birth Defects Research 109:1377-1385, 2017.© 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Lais Fajersztajn
- LIM 05 Departamento de Patologia, Hospital da Clinicas, Faculdade de Medicina Universidade de Sao Paulo, Sao Paulo, SP, Brasil
| | - Mariana Matera Veras
- LIM 05 Departamento de Patologia, Hospital da Clinicas, Faculdade de Medicina Universidade de Sao Paulo, Sao Paulo, SP, Brasil
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16
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Minuth WW. Concepts for a therapeutic prolongation of nephrogenesis in preterm and low-birth-weight babies must correspond to structural-functional properties in the nephrogenic zone. Mol Cell Pediatr 2017; 4:12. [PMID: 29218481 PMCID: PMC5721096 DOI: 10.1186/s40348-017-0078-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 11/20/2017] [Indexed: 12/30/2022] Open
Abstract
Numerous investigations are dealing with anlage of the mammalian kidney and primary development of nephrons. However, only few information is available about the last steps in kidney development leading at birth to a downregulation of morphogen activity in the nephrogenic zone and to a loss of stem cell niches aligned beyond the organ capsule. Surprisingly, these natural changes in the developmental program display similarities to processes occurring in the kidneys of preterm and low-birth-weight babies. Although those babies are born at a time with a principally intact nephrogenic zone and active niches, a high proportion of them suffers on impairment of nephrogenesis resulting in oligonephropathy, formation of atypical glomeruli, and immaturity of parenchyma. The setting points out that up to date not identified noxae in the nephrogenic zone hamper primary steps of parenchyma development. In this situation, a possible therapeutic aim is to prolong nephrogenesis by medications. However, actual data provide information that administration of drugs is problematic due to an unexpectedly complex microanatomy of the nephrogenic zone, in niches so far not considered textured extracellular matrix and peculiar contacts between mesenchymal cell projections and epithelial stem cells via tunneling nanotubes. Thus, it remains to be figured out whether disturbance of morphogen signaling altered synthesis of extracellular matrix, disturbed cell-to-cell contacts, or modified interstitial fluid impair nephrogenic activity. Due to most unanswered questions, search for eligible drugs prolonging nephrogenesis and their reliable administration is a special challenge for the future.
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Affiliation(s)
- Will W Minuth
- Institute of Anatomy, University of Regensburg, 93053, Regensburg, Germany.
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17
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Lin J, Huang H, Lv G, Xu X, Lin W, Xu X, Cheng J, Zheng M. Chronic prenatal hypoxia impairs cochlear development, a mechanism involving connexin26 expression and promoter methylation. Int J Mol Med 2017; 41:852-858. [PMID: 29207085 PMCID: PMC5752184 DOI: 10.3892/ijmm.2017.3303] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 11/02/2017] [Indexed: 12/31/2022] Open
Abstract
Chronic prenatal hypoxia is a damaging to fetal development and may have various consequences, including hearing loss. Connexin 26 (Cx26) is one of the major protein subunits required for gap junction formation, and has an important role in maintaining homeostasis in the cochlea and normal hearing. Cx26 mutation and expression abnormality are closely associated with inherited nonsyndromic deafness, but the association between Cx26 and prenatal hypoxia is less established. The present study aimed to examine Cx26 expression and aberrant methylation the Cx26 promoter region in the cochlea from rats exposed to chronic prenatal hypoxia. Hematoxylin and eosin staining demonstrated that the number of hair cells in the organ of Corti were less in the hypoxia group. Reverse transcription-quantitative polymerase chain reaction and western blot analysis revealed that protein and mRNA levels of Cx26 were decreased in the hypoxia group compared with the control group. Further bisulfite sequencing analysis revealed that prenatal hypoxia significantly increased the methylation status of the promoter region of the Cx26 gene. These results demonstrate that chronic prenatal hypoxia caused hearing impairment, and suggest that promoter region hypermethylation and expression downregulation of Cx26 underlie the mechanism of action.
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Affiliation(s)
- Jingcang Lin
- Department of Anatomy, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, Fujian 350004, P.R. China
| | - Huang Huang
- Department of Histology and Embryology, Quanzhou Medical College, Quanzhou, Fujian 362100, P.R. China
| | - Guorong Lv
- Department of Medical Imaging, Quanzhou Medical College, Quanzhou, Fujian 362100, P.R. China
| | - Xiangyang Xu
- Department of Histology and Embryology, Quanzhou Medical College, Quanzhou, Fujian 362100, P.R. China
| | - Wendong Lin
- Department of Anatomy, Quanzhou Medical College, Quanzhou, Fujian 362100, P.R. China
| | - Xianyan Xu
- Department of Anatomy, Quanzhou Medical College, Quanzhou, Fujian 362100, P.R. China
| | - Jing Cheng
- Department of Histology and Embryology, Quanzhou Medical College, Quanzhou, Fujian 362100, P.R. China
| | - Ming Zheng
- Department of Anatomy, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, Fujian 350004, P.R. China
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18
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Gerosa C, Fanni D, Faa A, Van Eyken P, Ravarino A, Fanos V, Faa G. Low vascularization of the nephrogenic zone of the fetal kidney suggests a major role for hypoxia in human nephrogenesis. Int Urol Nephrol 2017; 49:1621-1625. [DOI: 10.1007/s11255-017-1630-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 05/25/2017] [Indexed: 12/11/2022]
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19
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Activation of Hypoxia Signaling in Stromal Progenitors Impairs Kidney Development. THE AMERICAN JOURNAL OF PATHOLOGY 2017; 187:1496-1511. [PMID: 28527294 DOI: 10.1016/j.ajpath.2017.03.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 03/22/2017] [Indexed: 01/16/2023]
Abstract
Intrauterine hypoxia is a reason for impaired kidney development. The cellular and molecular pathways along which hypoxia exerts effects on nephrogenesis are not well understood. They are likely triggered by hypoxia-inducible transcription factors (HIFs), and their effects appear to be dependent on the cell compartment contributing to kidney formation. In this study, we investigated the effects of HIF activation in the developing renal stroma, which also essentially modulates nephron development from the metanephric mesenchyme. HIF activation was achieved by conditional deletion of the von Hippel-Lindau tumor suppressor (VHL) protein in the forkhead box FOXD1 cell lineage, from which stromal progenitors arise. The resulting kidneys showed maturation defects associated with early postnatal death. In particular, nephron formation, tubular maturation, and the differentiation of smooth muscle, renin, and mesangial cells were impaired. Erythropoietin expression was strongly enhanced. Codeletion of VHL together with HIF2A but not with HIF1A led to apparently normal kidneys, and the animals reached normal age but were anemic because of low erythropoietin levels. Stromal deletion of HIF2A or HIF1A alone did not affect kidney development. These findings emphasize the relevance of sufficient intrauterine oxygenation for normal renal stroma differentiation, suggesting that chronic activity of HIF2 in stromal progenitors impairs kidney development. Finally, these data confirm the concept that normal stroma function is essential for normal tubular differentiation.
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