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      Tubular Regeneration: When Can the Kidney Regenerate from Injury and What Turns Failure into Success

      *

      Cardiorenal Medicine

      S. Karger AG

      Tubular damage, Kidney regeneration, Acute kidney injury

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          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Background: The most common intrarenal cause for acute kidney injury/renal failure is tubular damage. The kidney tubules are arranged as compartments of cellular mosaics to perform their functions, and at rest almost a fifth of the human ATP consumption is allotted to the reabsorption of substances from the filtrate, rendering especially the proximal tubules highly sensitive to oxygen and/or nutrient deprivation. Normally mitotically quiescent, the tubular epithelium shows a brisk regenerative response following injury if supportive care is offered, allowing functional restoration. Despite this, the cellular machinery behind the regenerative capacity is still not unequivocally defined. This is at odds with other epithelia such as those of the skin and intestine, where stem cells maintain a continuous flow of new cells from designated niches. Summary: This review discusses the classical concept of renal regeneration, i.e. stochastically surviving cells undergoing dedifferentiation (or epithelial-mesenchymal transition) followed by replenishment of the tubular epithelium. Furthermore however, this view has recently been challenged by the concept of organ-confined stem/progenitor cells, bone marrow-derived stem cells, or mesenchymal stem cells taking part in the regenerative events. Whereas results from animal models support the classical view, morphologically distinct cells have been demonstrated in human kidneys, requiring interpretation. This review presents some of the previous work and techniques and highlights issues that need to be reconciled. Key Messages: In adult humans,the kidney tubules contain scattered cells with a distinct set of markers and properties, such as increased robustness during tubular damage. These cells may be induced by injury or represent a resident progenitor cell pool. To date, animal studies using lineage-tracing methods argue for an inductive scenario. In humans, the situation is less clear and one might speculate that the cellular heterogeneity might reflect elements of cellular reprogramming to a progenitor-like state, perhaps by induction. Due to intense investigational efforts, however, a scientific consensus may soon be reached, which will benefit further research.

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          Most cited references 23

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          Isolation and characterization of multipotent progenitor cells from the Bowman's capsule of adult human kidneys.

          Regenerative medicine represents a critical clinical goal for patients with ESRD, but the identification of renal adult multipotent progenitor cells has remained elusive. It is demonstrated that in human adult kidneys, a subset of parietal epithelial cells (PEC) in the Bowman's capsule exhibit coexpression of the stem cell markers CD24 and CD133 and of the stem cell-specific transcription factors Oct-4 and BmI-1, in the absence of lineage-specific markers. This CD24+CD133+ PEC population, which could be purified from cultured capsulated glomeruli, revealed self-renewal potential and a high cloning efficiency. Under appropriate culture conditions, individual clones of CD24+CD133+ PEC could be induced to generate mature, functional, tubular cells with phenotypic features of proximal and/or distal tubules, osteogenic cells, adipocytes, and cells that exhibited phenotypic and functional features of neuronal cells. The injection of CD24+CD133+ PEC but not of CD24-CD133- renal cells into SCID mice that had acute renal failure resulted in the regeneration of tubular structures of different portions of the nephron. More important, treatment of acute renal failure with CD24+CD133+ PEC significantly ameliorated the morphologic and functional kidney damage. This study demonstrates the existence and provides the characterization of a population of resident multipotent progenitor cells in adult human glomeruli, potentially opening new avenues for the development of regenerative medicine in patients who have renal diseases.
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            Dedifferentiation and proliferation of surviving epithelial cells in acute renal failure.

            In contrast to the heart or brain, the kidney can completely recover from an ischemic or toxic insult that results in cell death. During recovery from ischemia/reperfusion injury, surviving tubular epithelial cells dedifferentiate and proliferate, eventually replacing the irreversibly injured tubular epithelial cells and restoring tubular integrity. Repair of the kidney parallels kidney organogenesis in the high rate of DNA synthesis and apoptosis and in patterns of gene expression. As has been shown by proliferating cell nuclear antigen and 5-bromo 2'-deoxyuridine labeling studies and, in unpublished studies, by counting mitotic spindles identified by labeling with antitubulin antibody, the proliferative response is rapid and extensive, involving many of the remaining cells of the proximal tubule. This extensive proliferative capacity is interpreted to reflect the intrinsic ability of the surviving epithelial cell to adapt to the loss of adjacent cells by dedifferentiating and proliferating. Adhesion molecules likely play important roles in the regulation of renal epithelial cell migration, proliferation, and differentiation, as do cytokines and chemokines. Better understanding of all of the characteristics resulting in dedifferentiation and proliferation of the proximal tubule epithelial cell and cell-cell and cell-matrix interactions important for this repair function will lead to novel approaches to therapies designed to facilitate the processes of recovery in humans.
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              Characterization of renal progenitors committed toward tubular lineage and their regenerative potential in renal tubular injury.

              Recent studies implicated the existence in adult human kidney of a population of renal progenitors with the potential to regenerate glomerular as well as tubular epithelial cells and characterized by coexpression of surface markers CD133 and CD24. Here, we demonstrate that CD133+CD24+ renal progenitors can be distinguished in distinct subpopulations from normal human kidneys based on the surface expression of vascular cell adhesion molecule 1, also known as CD106. CD133+CD24+CD106+ cells were localized at the urinary pole of Bowman's capsule, while a distinct population of scattered CD133+CD24+CD106- cells was localized in the proximal tubule as well as in the distal convoluted tubule. CD133+CD24+CD106+ cells exhibited a high proliferative rate and could differentiate toward the podocyte as well as the tubular lineage. By contrast, CD133+CD24+CD106- cells showed a lower proliferative capacity and displayed a committed phenotype toward the tubular lineage. Both CD133+CD24+CD106+ and CD133+CD24+CD106- cells showed higher resistance to injurious agents in comparison to all other differentiated cells of the kidney. Once injected in SCID mice affected by acute tubular injury, both of these populations displayed the capacity to engraft within the kidney, generate novel tubular cells, and improve renal function. These properties were not shared by other tubular cells of the adult kidney. Finally, CD133+CD24+CD106- cells proliferated upon tubular injury, becoming the predominating part of the regenerating epithelium in patients with acute or chronic tubular damage. These data suggest that CD133+CD24+CD106- cells represent tubular-committed progenitors that display resistance to apoptotic stimuli and exert regenerative potential for injured tubular tissue. Copyright © 2012 AlphaMed Press.
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                Author and article information

                Journal
                NEE
                Nephron Exp Nephrol
                10.1159/issn.1660-2129
                Cardiorenal Medicine
                S. Karger AG
                978-3-318-02677-1
                978-3-318-02678-8
                1660-2129
                2014
                May 2014
                19 May 2014
                : 126
                : 2
                : 76-81
                Affiliations
                Center for Molecular Pathology, Department of Laboratory Medicine, Lund University, Skåne University Hospital, Malmö, Sweden
                Author notes
                *Martin E. Johansson, Center for Molecular Pathology, Department of Laboratory Medicine, Lund University, Skåne University Hospital, Jan Waldenströms gata 59, SE-205 02 Malmö (Sweden), E-Mail martin.johansson@med.lu.se
                Article
                360671 Nephron Exp Nephrol 2014;126:76-81
                10.1159/000360671
                24854645
                © 2014 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 1, Pages: 6
                Categories
                Further Section

                Cardiovascular Medicine, Nephrology

                Tubular damage, Kidney regeneration, Acute kidney injury

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