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      Embryonic Renal Collecting Duct Cell Differentiation Is Influenced in a Concentration-Dependent Manner by the Electrolyte Environment

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          Abstract

          Background: During kidney development, the embryonic collecting duct (CD) epithelium develops into a heterogeneously composed epithelium consisting of principal and intercalated cells. It is unknown by which molecular mechanism the different cell types arise. We have experimental evidence that the electrolyte environment is involved in the process of terminal cell differentiation. Methods: Embryonic CD epithelia from neonatal rabbit kidneys were microsurgically isolated and maintained in gradient perfusion culture for 13 days under serum-free conditions. Controls were maintained in the same medium (Iscove’s modified Dulbecco’s medium; IMDM) on basal and luminal sides. Experimental series were performed with IMDM only on the basal side, while on the luminal side IMDM with increasing concentrations of NaCl was used. Finally, the development of principal and intercalated cell features was registered by immunohistochemical labeling with markers specific for adult CD cells. Results: Immunohistochemical markers show that the differentiation pattern is quite different when the embryonic CD epithelia are cultured in IMDM only as compared with specimens kept in IMDM supplemented with 3–24 mmol/l NaCl on the luminal cell side. First signs of changes in development were seen when low doses of 3–6 mmol/l NaCl were added. Conclusions: We conclude that facultative protein expression in embryonic CD epithelium is influenced by the electrolyte environment and starts to be upregulated after administration of unexpectedly low doses of 3–6 mmol/l NaCl added to the luminal perfusion culture medium and increases in a concentration-dependent manner.

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          Most cited references 9

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          The catalog of human cytokeratins: patterns of expression in normal epithelia, tumors and cultured cells.

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            Induction of early stages of kidney tubule differentiation by lithium ions.

            Kidney tubules develop by a mesenchyme-epithelium transition, normally induced by ureteric bud through a mechanism that remains obscure. Murine nephrogenesis in vitro has always required heterologous inducing cells. We have discovered that Li+ can elicit the early stages of epithelial differentiation in isolated nephrogenic mesenchyme. We have made detailed comparisons of the timing of morphoregulatory molecule expression between Li(+)-mediated induction and the traditional in vitro method using induction by spinal cord. Both followed the same program of early morphoregulatory molecule expression, though Li(+)-induced samples failed to progress into the later parts of the nephrogenic process. Mesenchymes induced by Li+ showed more DNA synthesis than controls, though less than those induced by spinal cord. Discovery of a chemical means to activate differentiation in the absence of heterologous tissue offers a new basis for studying molecular mechanisms regulating the early events of nephrogenesis, as well as for investigating transduction of inductive signals that initiate the process.
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              Developmental expression of urine concentration-associated genes and their altered expression in murine infantile-type polycystic kidney disease.

               C Tian,  V Gattone,  R Maser (1998)
              Currently, there is little understanding of what factors regulate the development of urine concentrating capability in normal or polycystic kidney. The present study examined the developmental expression of genes associated with urine concentration in developing mice, including C57BL/6J-cpk/cpk mice with autosomal recessive-infantile (AR) polycystic kidney disease (PKD). Concentration of urine requires: 1) medullary collecting ducts (CD) located within a hypertonic interstitium, 2) CD cell expression of functional arginine vasopressin V2 receptors (AVP-V2R), and 3) the presence of appropriate CD water channels (aquaporins, AQP 2 and 3). An increase in urine osmolarity, normally seen between 1 and 3 weeks of age, was absent in cpk cystic mice. Aldose reductase mRNA expression (a gene upregulated by medullary hyperosmolarity) increased in normal mice, but remained low in the cystic kidney, suggesting the absence of a hypertonic medullary interstitium. AVP-V2R, AQP2, and AQP3 mRNA expression normally increase between 7 and 14 days. However, all were dramatically overexpressed even at 7 days of age in the cpk kidney in vivo, but decreased in vitro. Activation of the AVP-V2 receptor stimulates the production of cAMP, a substance known to promote cyst enlargement. To determine if CD cAMP, generated from increased AVP-V2Rs, was accelerating the PKD, cystic mice and their normal littermates were treated with OPC31260, a relatively specific AVP-V2R antagonist. OPC31260 treatment of cystic mice led to an amelioration of the cystic enlargement and azotemia. Treatment also decreased renal AQP2 mRNA but increased AVP-V2R and AQP3 mRNA expression in vivo. AVP upregulates the expression of AVP-V2R, AQP2, and AQP3 mRNAs in vitro. Renal EGF, known to inhibit AVP-V2R activity, downregulates AVP-V2R mRNA in vitro. Brief in vivo EGF treatment, known to decrease PKD in cpk mice, led to increased expression of AVP-V2R, AQP2, and AQP3 mRNAs at 2 weeks in both normal and cystic mice but no change was evident at 3 weeks of age. In conclusion, the development of urinary concentration ability correlates with the development of an increased medullary osmotic gradient which is diminished in murine ARPKD. However, CD genes associated with this process are overexpressed in vivo but underexpressed in vitro in the cystic kidney. The overexpression and/or overactivity of the AVP-V2R appears to contribute to the progression of PKD since an AVP-V2R antagonist inhibits cystic renal enlargement in the cpk mouse.
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                Author and article information

                Journal
                AJN
                Am J Nephrol
                10.1159/issn.0250-8095
                American Journal of Nephrology
                S. Karger AG
                0250-8095
                1421-9670
                2001
                April 2001
                07 May 2001
                : 21
                : 2
                : 165-175
                Affiliations
                aDepartment of Anatomy, University of Regensburg, Germany; bDepartment of Cellular and Molecular Physiology, University of Nice, France
                Article
                46242 Am J Nephrol 2001;21:165–175
                10.1159/000046242
                11359027
                © 2001 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: 7, Tables: 3, References: 46, Pages: 11
                Product
                Self URI (application/pdf): https://www.karger.com/Article/Pdf/46242
                Categories
                Laboratory Investigation

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