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Patel M, Velagapudi C, Burns H, Doss R, Lee MJ, Mariappan MM, Wagner B, Arar M, Barnes VL, Abboud HE, Barnes JL. Mouse Metanephric Mesenchymal Cell-Derived Angioblasts Undergo Vasculogenesis in Three-Dimensional Culture. THE AMERICAN JOURNAL OF PATHOLOGY 2017; 188:768-784. [PMID: 29269120 DOI: 10.1016/j.ajpath.2017.10.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 09/25/2017] [Accepted: 10/30/2017] [Indexed: 10/18/2022]
Abstract
In vitro models for the investigation of renal vascular development are limited. We previously showed that isolated metanephric mesenchymal (MM) and ureteric bud (UB) cells grown in three-dimensional (3D) matrices formed organoids that consisted of primitive vascular structures surrounding a polarized epithelium. Here, we examined the potential of two principal effectors of vasculogenesis, vascular endothelial growth factor A (VEGF-A), and platelet-derived growth factor B chain (PDGF-BB), to stimulate MM cell differentiation. The results showed that MM cells possess angioblast characteristics by expressing phenotypic markers for endothelial and mesenchymal cells. UB cells synthesize VEGF-A and PDGF-BB proteins and RNA, whereas the MM cells express the respective cognate receptors, supporting their role in directional induction of vasculogenesis. VEGF-A stimulated proliferation of MM cells in monolayer and in 3D sponges but did not affect MM cell migration, organization, or vasculogenesis. However, PDGF-BB stimulated MM cell proliferation, migration, and vasculogenesis in monolayer and organization of the cells into primitive capillary-like assemblies in 3D sea sponge scaffolds in vitro. A role for PDGF-BB in vasculogenesis in the 3D MM/UB co-culture system was validated by direct interference with PDGF-BB or PDGF receptor-β cell interactions to implicate PDGF-BB as a primary effector of MM cell vasculogenesis. Thus, MM cells resemble early renal angioblasts that may provide an ideal platform for the investigation of renal vasculogenesis in vitro.
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Affiliation(s)
- Mandakini Patel
- Department of Medicine, Division of Nephrology, Audie Murphy Memorial Veterans Administration Hospital, South Texas Veterans Health Care System, San Antonio, Texas
| | - Chakradhar Velagapudi
- Department of Medicine, Division of Nephrology, Audie Murphy Memorial Veterans Administration Hospital, South Texas Veterans Health Care System, San Antonio, Texas
| | | | | | | | | | - Brent Wagner
- Department of Medicine, Division of Nephrology, Audie Murphy Memorial Veterans Administration Hospital, South Texas Veterans Health Care System, San Antonio, Texas; The Medical Research Service, Audie Murphy Memorial Veterans Administration Hospital, South Texas Veterans Health Care System, San Antonio, Texas
| | - Mazen Arar
- Department of Pediatrics, The University of Texas Health Science Center, San Antonio, Texas
| | | | - Hanna E Abboud
- Department of Medicine, Division of Nephrology, Audie Murphy Memorial Veterans Administration Hospital, South Texas Veterans Health Care System, San Antonio, Texas; The Medical Research Service, Audie Murphy Memorial Veterans Administration Hospital, South Texas Veterans Health Care System, San Antonio, Texas
| | - Jeffrey L Barnes
- Department of Medicine, Division of Nephrology, Audie Murphy Memorial Veterans Administration Hospital, South Texas Veterans Health Care System, San Antonio, Texas; Probetex, Inc., San Antonio, Texas; The Medical Research Service, Audie Murphy Memorial Veterans Administration Hospital, South Texas Veterans Health Care System, San Antonio, Texas.
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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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Fanni D, Gerosa C, Vinci L, Ambu R, Dessì A, Eyken PV, Fanos V, Faa G. Interstitial stromal progenitors during kidney development: here, there and everywhere. J Matern Fetal Neonatal Med 2016; 29:3815-20. [PMID: 26866875 DOI: 10.3109/14767058.2016.1147553] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In recent years, the renal interstitium has been identified as the site of multiple cell types, giving rise to multiple contiguous cellular networks with multiple fundamental structural and functional roles. Few studies have been carried out on the morphological and functional properties of the stromal/interstitial renal cells during the intrauterine life. This work was aimed at reviewing the peculiar features of renal interstitial stem/progenitor cells involved in kidney development. The origin of the renal interstitial progenitor cells remains unknown. During kidney development, besides the Six2 + cells of the cap mesenchyme, a self-renewing progenitor population, characterized by the expression of Foxd1, represents the first actor of the non-nephrogenic lineage. Foxd1 + interstitial progenitors originate the cortical and the renal medullary interstitial progenitors. Here, the most important stromal/interstitial compartments present in the developing human kidney will be analyzed: capsular stromal cells, cortical interstitial cells, medullary interstitial cells, the interstitium inside the renal stem cell niche, Hilar interstitial cells and Ureteric interstitial cells. Data reported here indicate that the different interstitial compartments of the developing kidney are formed by different cell types that characterize the different renal areas. Further studies are needed to better characterize the different pools of renal interstitial progenitors and their role in human nephrogenesis.
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Affiliation(s)
- Daniela Fanni
- a Division of Pathology , Department of Surgical Sciences, University of Cagliari , Cagliari , Italy
| | - Clara Gerosa
- a Division of Pathology , Department of Surgical Sciences, University of Cagliari , Cagliari , Italy
| | - Laura Vinci
- a Division of Pathology , Department of Surgical Sciences, University of Cagliari , Cagliari , Italy
| | - Rossano Ambu
- a Division of Pathology , Department of Surgical Sciences, University of Cagliari , Cagliari , Italy
| | - Angelica Dessì
- b Department of Surgical Sciences , NICU Center and Puericulture Institute and Neonatal Section, University of Cagliari , Cagliari , Italy , and
| | - Peter Van Eyken
- c Department of Pathology , University Hospitals, KU , Leuven , Belgium
| | - Vassilios Fanos
- b Department of Surgical Sciences , NICU Center and Puericulture Institute and Neonatal Section, University of Cagliari , Cagliari , Italy , and
| | - Gavino Faa
- a Division of Pathology , Department of Surgical Sciences, University of Cagliari , Cagliari , Italy
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Minuth WW, Denk L. Special Morphological Features at the Interface of the Renal Stem/Progenitor Cell Niche Force to Reinvestigate Transport of Morphogens During Nephron Induction. Biores Open Access 2016; 5:49-60. [PMID: 26862472 PMCID: PMC4744892 DOI: 10.1089/biores.2015.0039] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Formation of a nephron depends on reciprocal signaling of different morphogens between epithelial and mesenchymal cells within the renal stem/progenitor cell niche. Previously, it has been surmised that a close proximity exists between both involved cell types and that morphogens are transported between them by diffusion. However, actual morphological data illustrate that mesenchymal and epithelial stem/progenitor cell bodies are separated by a striking interface. Special fixation of specimens by glutaraldehyde (GA) solution including cupromeronic blue, ruthenium red, or tannic acid for electron microscopy depicts that the interface is not void but filled in extended areas by textured extracellular matrix. Surprisingly, projections of mesenchymal cells cross the interface to contact epithelial cells. At those sites the plasma membranes of a mesenchymal and an epithelial cell are connected via tunneling nanotubes. Regarding detected morphological features in combination with involved morphogens, their transport cannot longer be explained solely by diffusion. Instead, it has to be sorted according to biophysical properties of morphogens and to detected environment. Thus, the new working hypothesis is that morphogens with good solubility such as glial cell line-derived neurotrophic factor (GDNF) or fibroblast growth factors (FGFs) are transported by diffusion. Morphogens with minor solubility such as bone morphogenetic proteins (BMPs) are secreted and stored for delivery on demand in illustrated extracellular matrix. In contrast, morphogens with poor solubility such as Wnts are transported in mesenchymal cell projections along the plasma membrane or via illustrated tunneling nanotubes. However, the presence of an intercellular route between mesenchymal and epithelial stem/progenitor cells by tunneling nanotubes also makes it possible that all morphogens are transported this way.
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Affiliation(s)
- Will W Minuth
- Department of Molecular and Cellular Anatomy, University of Regensburg , Regensburg, Germany
| | - Lucia Denk
- Department of Molecular and Cellular Anatomy, University of Regensburg , Regensburg, Germany
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Minuth WW, Denk L. When morphogenetic proteins encounter special extracellular matrix and cell-cell connections at the interface of the renal stem/progenitor cell niche. Anat Cell Biol 2015; 48:1-9. [PMID: 25806116 PMCID: PMC4371175 DOI: 10.5115/acb.2015.48.1.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 01/30/2015] [Accepted: 02/17/2015] [Indexed: 12/18/2022] Open
Abstract
Reciprocal exchange of morphogenetic proteins between epithelial and mesenchymal cells in a stem/progenitor cell niche results in formation of a nephron. To maintain diffusion of morphogenetic proteins, it is assumed that a close contact exists between involved cells. However, recent publications underline that both types of stem/progenitor cells are separated by a striking interface. To explore this microarchitecture in detail, neonatal rabbit kidneys were fixed in traditional glutaraldehyde (GA) solution for transmission electron microscopy. For contrast enhancing specimens were fixed in GA solution including cupromeronic blue, ruthenium red or tannic acid. To record same perspectives, embedded blocks of parenchyma were cut in exactly orientated vertical and transverse planes to lining collecting ducts. Electron microscopy of specimens fixed by traditional GA solution illustrates a spatial separation of stem/progenitor cells and an unobstrusively looking interface. In contrast, advanced fixation of specimens in GA solution including cupromeronic blue, ruthenium red and tannic acid unmasks earlier not visible extracellular matrix. In addition, projections of mesenchymal cells covered by matrix cross the interface to contact epithelial cells. Surprisingly, the end of a mesenchymal cell projection does not dangle but is enclosed in a fitting sleeve and connected via tunneling nanotubes with the plasma membrane of an epithelial cell. Regarding this complex ensemble the question is to what extent illustrated cell-cell connections and extracellular matrix are involved in communication and transmission of morphogenetic proteins during induction of a nephron.
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Affiliation(s)
- Will W Minuth
- Institute of Molecular and Cellular Anatomy, University of Regensburg, Regensburg, Germany
| | - Lucia Denk
- Institute of Molecular and Cellular Anatomy, University of Regensburg, Regensburg, Germany
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Minuth WW, Denk L. Tannic acid label indicates abnormal cell development coinciding with regeneration of renal tubules. BMC Clin Pathol 2014; 14:34. [PMID: 25071418 PMCID: PMC4112905 DOI: 10.1186/1472-6890-14-34] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 07/11/2014] [Indexed: 12/29/2022] Open
Abstract
Background Stem/progenitor cells are in the focus of research as a future therapeutic option to stimulate regeneration in diseased renal parenchyma. However, current data indicate that successful seeding of implanted stem/progenitor cells is prevented by harmful interstitial fluid and altered extracellular matrix. To find out possible parameters for cell adaptation, the present investigation was performed. Methods Renal stem/progenitor cells were mounted in an artificial interstitium for perfusion culture. Exposure to chemically defined but CO2-independent culture media was tested during 13 days. Cell biological features were then analyzed by histochemistry, while structural details were investigated by transmission electron microscopy after conventional and improved fixation of specimens. Results Culture of renal stem/progenitor cells as well in Leibovitz’s L-15 Medium as CO2 Independent Medium shows in fluorescence microscopy spatial development of numerous tubules. Specimens of both media fixed by conventional glutaraldehyde exhibit in electron microscopy a homogeneous cell population in developed tubules. In contrast, fixation by glutaraldehyde including tannic acid illuminates that dispersed dark marked cells of unknown function are present. The screening further demonstrates that the dark cell type does not comply with cells found in embryonic, maturing or matured renal parenchyma. Conclusions The actual data show that development of abnormal cell features must be taken into account, when regeneration of renal tubules is simulated under in vitro conditions.
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Affiliation(s)
- Will W Minuth
- Department of Molecular and Cellular Anatomy, University of Regensburg, University Street 31, D-93053 Regensburg, Germany
| | - Lucia Denk
- Department of Molecular and Cellular Anatomy, University of Regensburg, University Street 31, D-93053 Regensburg, Germany
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Minuth WW, Denk L. Structural links between the renal stem/progenitor cell niche and the organ capsule. Histochem Cell Biol 2014; 141:459-71. [PMID: 24429831 DOI: 10.1007/s00418-014-1179-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/02/2014] [Indexed: 11/30/2022]
Abstract
A special feature of the renal stem/progenitor cell niche is its always close neighborhood to the capsule during organ development. To explore this link, neonatal kidney was investigated by histochemistry and transmission electron microscopy. For adequate contrasting, fixation of specimens was performed by glutaraldehyde including tannic acid. The immunohistochemical data illustrate that renal stem/progenitor cells are not distributed randomly but are positioned specially to the capsule. Epithelial stem/progenitor cells are found to be enclosed by the basal lamina at a collecting duct (CD) ampulla tip. Only few layers of mesenchymal cells are detected between epithelial cells and the capsule. Most impressive, numerous microfibers reacting with soybean agglutinin, anti-collagen I and III originate from the basal lamina at a CD ampulla tip and line between mesenchymal stem/progenitor cells to the inner side of the capsule. This specific arrangement holds together both types of stem/progenitor cells in a cage and fastens the niche as a whole at the capsule. Electron microscopy further illustrates that the stem/progenitor cell niche is in contact with a tunnel system widely spreading between atypical smooth muscle cells at the inner side of the capsule. It seems probable that stem/progenitor cells are supplied here by interstitial fluid.
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Affiliation(s)
- Will W Minuth
- Molecular and Cellular Anatomy, University of Regensburg, University Street 31, 93053, Regensburg, Germany,
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Thévenin AF, Kowal TJ, Fong JT, Kells RM, Fisher CG, Falk MM. Proteins and mechanisms regulating gap-junction assembly, internalization, and degradation. Physiology (Bethesda) 2014; 28:93-116. [PMID: 23455769 DOI: 10.1152/physiol.00038.2012] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Gap junctions (GJs) are the only known cellular structures that allow a direct cell-to-cell transfer of signaling molecules by forming densely packed arrays or "plaques" of hydrophilic channels that bridge the apposing membranes of neighboring cells. The crucial role of GJ-mediated intercellular communication (GJIC) for all aspects of multicellular life, including coordination of development, tissue function, and cell homeostasis, has been well documented. Assembly and degradation of these membrane channels is a complex process that includes biosynthesis of the connexin (Cx) subunit proteins (innexins in invertebrates) on endoplasmic reticulum (ER) membranes, oligomerization of compatible subunits into hexameric hemichannels (connexons), delivery of the connexons to the plasma membrane (PM), head-on docking of compatible connexons in the extracellular space at distinct locations, arrangement of channels into dynamic spatially and temporally organized GJ channel plaques, as well as internalization of GJs into the cytoplasm followed by their degradation. Clearly, precise modulation of GJIC, biosynthesis, and degradation are crucial for accurate function, and much research currently addresses how these fundamental processes are regulated. Here, we review posttranslational protein modifications (e.g., phosphorylation and ubiquitination) and the binding of protein partners (e.g., the scaffolding protein ZO-1) known to regulate GJ biosynthesis, internalization, and degradation. We also look closely at the atomic resolution structure of a GJ channel, since the structure harbors vital cues relevant to GJ biosynthesis and turnover.
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Affiliation(s)
- Anastasia F Thévenin
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, USA
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Minuth WW, Denk L. Advanced fixation for transmission electron microscopy unveils special extracellular matrix within the renal stem/progenitor cell niche. Methods Mol Biol 2014; 1212:21-37. [PMID: 25063501 DOI: 10.1007/7651_2014_93] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
As well in light as in transmission electron microscopy can be seen that the renal stem/progenitor cell niche shows a special arrangement of two different kinds of stem/progenitor cells. Epithelial cells are found in the tip of an ureteric bud derived CD ampulla encircled by a special basal lamina. Mesenchymal cells are separated from them by a striking interstitial interface. Specimens fixed by conventional glutaraldehyde solution show that the interface looks bright and unremarkable. In contrast, fixation of specimens with glutaraldehyde in combination with cupromeronic blue, ruthenium red, or tannic acid illustrates that the interface contains a remarkable network of extracellular matrix spanning between epithelial and mesenchymal stem/progenitor cells. After unpacking this particular extracellular matrix for electron microscopy, elaboration of related functions such as structural composition of contained molecules, binding of morphogenetic factors, and influence on parenchyma development is under current experimental work.
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Affiliation(s)
- Will W Minuth
- Molecular and Cellular Anatomy, University of Regensburg, University Street 31, D-93053, Regensburg, Germany,
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Minuth WW, Denk L. The interstitial interface within the renal stem/progenitor cell niche exhibits an unique microheterogeneous composition. Int J Mol Sci 2013; 14:13657-69. [PMID: 23812083 PMCID: PMC3742209 DOI: 10.3390/ijms140713657] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Revised: 06/04/2013] [Accepted: 06/18/2013] [Indexed: 12/11/2022] Open
Abstract
Repair of parenchyma by stem/progenitor cells is seen as a possible alternative to cure acute and chronic renal failure in future. To learn about this therapeutic purpose, the formation of nephrons during organ growth is under focus of present research. This process is triggered by numerous morphogenetic interactions between epithelial and mesenchymal cells within the renal stem/progenitor cell niche. Recent data demonstrate that an astonishingly wide interstitial interface separates both types of stem/progenitor cells probably controlling coordinated cell-to-cell communication. Since conventional fixation by glutaraldehyde (GA) does not declare in transmission electron microscopy the spatial separation, improved contrasting procedures were applied. As a consequence, the embryonic cortex of neonatal rabbit kidneys was fixed in solutions containing glutaraldehyde in combination with cupromeronic blue, ruthenium red or tannic acid. To obtain a comparable view to the renal stem/progenitor cell niche, the specimens had to be orientated along the cortico-medullary axis of lining collecting ducts. Analysis of tissue samples fixed with GA, in combination with cupromeronic blue, demonstrates demasked extracellular matrix. Numerous braces of proteoglycans cover, as well, the basal lamina of epithelial stem/progenitor cells as projections of mesenchymal stem/progenitor cells crossing the interstitial interface. Fixation with GA containing ruthenium red or tannic acid illustrates strands of extracellular matrix that originate from the basal lamina of epithelial stem/progenitor cells and line through the interstitial interface. Thus, for the first time, improved contrasting techniques make it possible to analyze in detail a microheterogeneous composition of the interstitial interface within the renal stem/progenitor cell niche.
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Affiliation(s)
- Will W Minuth
- Department of Molecular and Cellular Anatomy, University of Regensburg, Regensburg D-93053, Germany.
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Minuth WW, Denk L. Cell projections and extracellular matrix cross the interstitial interface within the renal stem/progenitor cell niche: accidental, structural or functional cues? Nephron Clin Pract 2013; 122:131-40. [PMID: 23735962 DOI: 10.1159/000351129] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 04/03/2013] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND During nephron induction, morphogenetic molecules are reciprocally exchanged between epithelial and mesenchymal stem/progenitor cells within the renal stem/progenitor cell niche. That these molecules remain concentrated, it is assumed that both cell populations stand in close contact to each other. However, recently published data illustrate that epithelial and mesenchymal cells are separated by an astonishingly wide interstitial interface. METHODS To gain deeper morphological insights into the spatial distribution of mesenchymal and epithelial stem/progenitor cells, the embryonic zone of neonatal rabbit kidney was fixed either with glutaraldehyde (GA) or in a combination with cupromeronic blue, ruthenium red or tannic acid. Transmission electron microscopy was then performed on exactly orientated sections. RESULTS Conventional fixation with GA illustrates that epithelial and mesenchymal stem/progenitor cells are separated by a bright but inconspicuously looking interstitial interface. In contrast, fixation of specimens in GA containing cupromeronic blue, ruthenium red or tannic acid elucidates that part of the interstitial interface exhibits a special extracellular matrix extending like woven strands between mesenchymal and epithelial stem/progenitor cells. In parallel, filigree projections from mesenchymal stem/progenitor cells cross the interstitial interface to penetrate the basal lamina of epithelial cells. Fusion of the plasma membranes cannot be observed. Instead, touching mesenchymal cell projections form a cone at the contact site with tunneling nanotubes. CONCLUSIONS The results demonstrate that the contact between mesenchymal and epithelial stem/progenitor cells does not form accidentally but physiologically and appears to belong to a suspected system involved in the exchange of morphogenetic information.
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Affiliation(s)
- Will W Minuth
- Institute for Molecular and Cellular Anatomy, University of Regensburg, Regensburg, Germany. will.minuth @ vkl.uni-regensburg.de
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