Developmental aspects of secondary palate formation

Research on development of the secondary palate has, in the past, dealt primarily with morphological aspects of shelf elevation and fusion. The many factors thought to be involved in palatal elevation, such as fetal neuromuscular activity and growth of the cranial base and mandible, as well as production of extracellular matrix and contractile elements in the palate, are mostly based on gross, light microscopic, morphometric or histochemical observations. Recently, more biochemical procedures have been utilized to describe palatal shelf elevation. Although these studies strongly suggest that palatal extracellular matrix plays a major role in shelf movement, interpretation of these data remains difficult owing to the complexity of tissue interactions involved in craniofacial development. Shelf elevation does not appear to involve a single motive factor, but rather a coordinated interaction of all of the abovementioned developmental events. Further analysis of mechanisms of shelf elevation requires development of new, and refinement of existing, in vitro procedures. A system that enables one to examine shelf elevation in vitro would allow more meaningful analysis of the relative importance of the various components in shelf movement. Much more is known about fusion of the palatal shelves, owing in large part to in vitro studies. Fusion of the apposing shelves, both in vivo and in vitro, is dependent upon adhesion and cell death of the midline epithelial cells. Adhesion between apposing epithelial surfaces appears to involve epithelial cell surface macromolecules. Further analysis of palatal epithelial adhesion should be directed towards characterization of those cell surface components responsible for this adhesive interaction. Midline epithelial cells cease DNA synthesis 24–36 h before shelf elevation and contact, become active in the synthesis of cell surface glycoproteins, and subsequently manifest morphological signs of necrosis. Death of the midline epithelial cells is thought to involve a programmed, lysosomal-mediated autolysis. Information regarding the appearance, distribution and quantitation of epithelial hydrolytic enzymes is needed. The control mechanisms which regulate adhesiveness and cell death in the palatal epithelium are not fully understood. Although palatal epithelial-mesenchymal recombination experiments have demonstrated a close relationship between the underlying mesenchyme and the differentiating epithelium, the molecular mechanism of interaction remains unclear. Recently cyclic nucleotides have been implicated as possible mediators of palatal epithelial differentiation. The developing secondary palate therefore offers a system whereby one can probe a variety of developmental phenomena. Cellular adhesion, programmed cell death and epithelial- mesenchymal interactions are all amenable to both morphological as well as bio- chemical analysis. Although research in the field of secondary palate development has been extensive, there still remain many provocative questions relating to normal development of this structure.

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Thyroid Hormone Induces Apoptosis in Primary Cell Cultures of Tadpole Intestine: Cell Type Specificity and Effects of Extracellular Matrix

The Journal of Cell Biology ◽

10.1083/jcb.139.6.1533 ◽

1997 ◽

Vol 139 (6) ◽

pp. 1533-1543 ◽

Cited By ~ 51

Author(s):

Yuan Su ◽

Yufang Shi ◽

Melissa A. Stolow ◽

Yun-Bo Shi

Keyword(s):

Extracellular Matrix ◽

Cell Death ◽

Thyroid Hormone ◽

Epithelial Cells ◽

Mammalian Cell ◽

Cell Types ◽

Specific Gene ◽

Causative Role ◽

Cell Type Specificity

Thyroid hormone (T3 or 3,5,3′-triiodothyronine) plays a causative role during amphibian metamorphosis. To investigate how T3 induces some cells to die and others to proliferate and differentiate during this process, we have chosen the model system of intestinal remodeling, which involves apoptotic degeneration of larval epithelial cells and proliferation and differentiation of other cells, such as the fibroblasts and adult epithelial cells, to form the adult intestine. We have established in vitro culture conditions for intestinal epithelial cells and fibroblasts. With this system, we show that T3 can enhance the proliferation of both cell types. However, T3 also concurrently induces larval epithelial apoptosis, which can be inhibited by the extracellular matrix (ECM). Our studies with known inhibitors of mammalian cell death reveal both similarities and differences between amphibian and mammalian cell death. These, together with gene expression analysis, reveal that T3 appears to simultaneously induce different pathways that lead to specific gene regulation, proliferation, and apoptotic degeneration of the epithelial cells. Thus, our data provide an important molecular and cellular basis for the differential responses of different cell types to the endogenous T3 during metamorphosis and support a role of ECM during frog metamorphosis.

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Preliminary characterization of cell surface-extracellular matrix linkage complexes in cultured retinal pigmented epithelial cells

Experimental Cell Research ◽

10.1016/0014-4827(87)90270-9 ◽

1987 ◽

Vol 171 (1) ◽

pp. 259-264 ◽

Cited By ~ 9

Author(s):

Kursad Turksen ◽

Michal Opas ◽

Vitauts I. Kalnins

Keyword(s):

Extracellular Matrix ◽

Epithelial Cells ◽

Cell Surface ◽

Preliminary Characterization ◽

Retinal Pigmented Epithelial Cells

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Helicobacter pylori Induces Gastric Epithelial Cell Apoptosis in Association with Increased Fas Receptor Expression

Infection and Immunity ◽

10.1128/iai.67.8.4237-4242.1999 ◽

1999 ◽

Vol 67 (8) ◽

pp. 4237-4242 ◽

Cited By ~ 106

Author(s):

Nicola L. Jones ◽

Andrew S. Day ◽

Hilary A. Jennings ◽

Philip M. Sherman

Keyword(s):

Cell Death ◽

Helicobacter Pylori ◽

Epithelial Cells ◽

Receptor Expression ◽

Gastric Epithelial Cells ◽

Ags Cells ◽

Fas Receptor ◽

Epithelial Cell Apoptosis ◽

H Pylori

ABSTRACT The mechanisms involved in mediating the enhanced gastric epithelial cell apoptosis observed during infection withHelicobacter pylori in vivo are unknown. To determine whether H. pylori directly induces apoptosis of gastric epithelial cells in vitro and to define the role of the Fas-Fas ligand signal transduction cascade, human gastric epithelial cells were infected with H. pylori for up to 72 h under microaerophilic conditions. As assessed by both transmission electron microscopy and fluorescence microscopy, incubation with acagA-positive, cagE-positive, VacA-positive clinical H. pylori isolate stimulated an increase in apoptosis compared to the apoptosis of untreated AGS cells (16.0% ± 2.8% versus 5.9% ± 1.4%, P < 0.05) after 72 h. In contrast, apoptosis was not detected following infection withcagA-negative, cagE-negative, VacA-negative clinical isolates or a Campylobacter jejuni strain. In addition to stimulating apoptosis, infection with H. pylorienhanced Fas receptor expression in AGS cells to a degree comparable to that of treatment with a positive control, gamma interferon (12.5 ng/ml) (148% ± 24% and 167% ± 24% of control, respectively). The enhanced Fas receptor expression was associated with increased sensitivity to Fas-mediated cell death. Ligation of the Fas receptor with an agonistic monoclonal antibody resulted in an increase in apoptosis compared to the apoptosis of cells infected with the bacterium alone (38.5% ± 7.1% versus 16.0% ± 2.8%,P < 0.05). Incubation with neutralizing anti-Fas antibody did not prevent apoptosis of H. pylori-infected cells. Taken together, these findings demonstrate that the gastric pathogen H. pylori stimulates apoptosis of gastric epithelial cells in vitro in association with the enhanced expression of the Fas receptor. These data indicate a role for Fas-mediated signaling in the programmed cell death that occurs in response toH. pylori infection.

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Stimulation of corneal differentiation by interaction between cell surface and extracellular matrix. I. Morphometric analysis of transfilter "induction".

The Journal of Cell Biology ◽

10.1083/jcb.66.2.275 ◽

1975 ◽

Vol 66 (2) ◽

pp. 275-291 ◽

Cited By ~ 71

Author(s):

L Meier ◽

E D Hay

Keyword(s):

Extracellular Matrix ◽

Electron Microscope ◽

Cell Surface ◽

Pore Size ◽

Collagen Synthesis ◽

Lens Capsule ◽

Physical Contact ◽

Corneal Epithelial ◽

Cell Processes

The present study was undertaken to determine whether or not physical contact with the substratum is essential for the stimulatory effect of extracellular matrix (ECM) on corneal epithelial collagen synthesis. Previous studies showed that collagenous substrata stimulate isolated epithelia to produce three times as much collagen as they produce on noncollagenous substrate; killed collagenous substrata (e.g., lens capsule) are just as effective as living substrata (e.g., living lens) in promoting the production of new corneal stroma in vitro. In the experiments to be reported here, corneal epithelia were placed on one side of Nucleopore filters of different pore sizes and killed lens capsule on the other, with the expectation that contact of the reacting cells with the lens ECM should be limited by the number and size of the cell processes that can tranverse the pores. Transfilter cultures were grown for 24 h in [3H]proline-containing median and incorporation of isotope into hot trichloroacetic acid-soluble protein was used to measure corneal epithelial collagen production. Epithelial collagen synthesis increases directly as the size of the pores in the interposed filter increases and decreases as the thickness of the filter layer increases. Cell processes within Nucleopore filters were identified with the transmission electron microscope with difficulty; with the scanning electron microscope, however, the processes could easily be seen emerging from the undersurface of even 0.1-mum pore size filters. Morphometric techniques were used to show that cell surface area thus exposed to the underlying ECM is linearly correlated with enhancement of collagen synthesis. Epithelial cell processes did not pass through ultrathin (25-mum thick) 0.45-mum pore size Millipore filters nor did "induction" occur across them. The results are discussed in relation to current theories of embryonic tissue interaction.

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The influence of the epithelium on palate shelf reorientation

Development ◽

10.1242/dev.88.1.265 ◽

1985 ◽

Vol 88 (1) ◽

pp. 265-279

Author(s):

Robert F. Bulleit ◽

Ernest F. Zimmerman

Keyword(s):

Extracellular Matrix ◽

Wound Healing ◽

Basement Membrane ◽

Soft Palate ◽

Hard Palate ◽

Significant Inhibition ◽

Oral Epithelium ◽

Secondary Palate ◽

Intrinsic Forces

The intrinsic forces necessary for directing the reorientation of the secondary palate appear to reside in the anterior two thirds of the palate or presumptive hard palate. The hard palate could reorient regardless of whether it was intact or separated from the posterior third or presumptive soft palate. The soft palate could only reorient if the palate shelves are left intact. These intrinsic forces, within the hard palate, may be mediated by the mesenchymal cells, their extracellular matrix, or the epithelium surrounding the shelves. This latter possibly was tested by removing the epithelium, from either the presumptive oral or nasal surface followed by measurement of reorientation in vitro. Only after removal of the oral epithelium was a significant inhibition in reorientation observed. The treatment used to remove the epithelium, EDTA and scraping, was shown to remove 41 % of the oral epithelium leaving the majority of the basement membrane intact. The observed inhibition of reorientation did not appear to be a consequence of wound healing. Creation of wounds twice the area that was observed after treatment with EDTA and scraping inhibited reorientation minimally. These results suggest that the epithelium and particularly the anterior oral epithelium plays a major role in the reorientation of the murine secondary palate.

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Dynamic extracellular matrix stiffening induces a phenotypic transformation and a migratory shift in epithelial cells

Integrative Biology ◽

10.1093/intbio/zyaa012 ◽

2020 ◽

Vol 12 (6) ◽

pp. 161-174

Author(s):

Shane C Allen ◽

Jessica A Widman ◽

Anisha Datta ◽

Laura J Suggs

Keyword(s):

Extracellular Matrix ◽

Epithelial Cells ◽

Epithelial To Mesenchymal Transition ◽

Soft Tissue Tumors ◽

Tumor Formation ◽

Matrix Stiffness ◽

Mesenchymal Transition ◽

Cell Clusters

Abstract Soft tissue tumors, including breast cancer, become stiffer throughout disease progression. This increase in stiffness has been shown to correlate to malignant phenotype and epithelial-to-mesenchymal transition (EMT) in vitro. Unlike current models, utilizing static increases in matrix stiffness, our group has previously created a system that allows for dynamic stiffening of an alginate–matrigel composite hydrogel to mirror the native dynamic process. Here, we utilize this system to evaluate the role of matrix stiffness on EMT and metastasis both in vitro and in vivo. Epithelial cells were seen to lose normal morphology and become protrusive and migratory after stiffening. This shift corresponded to a loss of epithelial markers and gain of mesenchymal markers in both the cell clusters and migrated cells. Furthermore, stiffening in a murine model reduced tumor burden and increased migratory behavior prior to tumor formation. Inhibition of FAK and PI3K in vitro abrogated the morphologic and migratory transformation of epithelial cell clusters. This work demonstrates the key role extracellular matrix stiffening has in tumor progression through integrin signaling and, in particular, its ability to drive EMT-related changes and metastasis.

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Bcl-2 overexpression in type II epithelial cells does not prevent hyperoxia-induced acute lung injury in mice

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00212.2009 ◽

2010 ◽

Vol 299 (3) ◽

pp. L312-L322 ◽

Cited By ~ 8

Author(s):

Isabelle Métrailler-Ruchonnet ◽

Alessandra Pagano ◽

Stéphanie Carnesecchi ◽

Karim Khatib ◽

Pedro Herrera ◽

...

Keyword(s):

Cell Death ◽

Epithelial Cells ◽

Lung Injury ◽

Ex Vivo ◽

Lung Damage ◽

Type Ii Cells ◽

Type Ii ◽

Lung Weight

Bcl-2 is an anti-apoptotic molecule preventing oxidative stress damage and cell death. We have previously shown that Bcl-2 is able to prevent hyperoxia-induced cell death when overexpressed in a murine fibrosarcoma cell line L929. We hypothesized that its specific overexpression in pulmonary epithelial type II cells could prevent hyperoxia-induced lung injury by protecting the epithelial side of the alveolo-capillary barrier. In the present work, we first showed that in vitro Bcl-2 can rescue murine pulmonary epithelial cells (MLE12) from oxygen-induced cell apoptosis, as shown by analysis of LDH release, annexin V/propidium staining, and caspase-3 activity. We then generated transgenic mice overexpressing specifically Bcl-2 in lung epithelial type II cells under surfactant protein C (SP-C) promoter (Tg-Bcl-2) and exposed them to hyperoxia. Bcl-2 did not hinder hyperoxia-induced mitochondria and DNA oxidative damage of type II cell in vivo. Accordingly, lung damage was identical in both Tg-Bcl-2 and littermate mice strains, as measured by lung weight, bronchoalveolar lavage, and protein content. Nevertheless, we observed a significant lower number of TUNEL-positive cells in type II cells isolated from Tg-Bcl-2 mice exposed to hyperoxia compared with cells isolated from littermate mice. In summary, these results show that although Bcl-2 overexpression is able to prevent hyperoxia-induced cell death at single cell level in vitro and ex vivo, it is not sufficient to prevent cell death of parenchymal cells and to protect the lung from acute damage in mice.

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MT1-MMP–dependent neovessel formation within the confines of the three-dimensional extracellular matrix

The Journal of Cell Biology ◽

10.1083/jcb.200405001 ◽

2004 ◽

Vol 167 (4) ◽

pp. 757-767 ◽

Cited By ~ 223

Author(s):

Tae-Hwa Chun ◽

Farideh Sabeh ◽

Ichiro Ota ◽

Hedwig Murphy ◽

Kevin T. McDonagh ◽

...

Keyword(s):

Extracellular Matrix ◽

Endothelial Cells ◽

Cell Surface ◽

Type I Collagen ◽

Ex Vivo ◽

Three Dimensional ◽

Collagenolytic Activity ◽

Type I ◽

Ex Vivo Model

During angiogenesis, endothelial cells initiate a tissue-invasive program within an interstitial matrix comprised largely of type I collagen. Extracellular matrix–degradative enzymes, including the matrix metalloproteinases (MMPs) MMP-2 and MMP-9, are thought to play key roles in angiogenesis by binding to docking sites on the cell surface after activation by plasmin- and/or membrane-type (MT) 1-MMP–dependent processes. To identify proteinases critical to neovessel formation, an ex vivo model of angiogenesis has been established wherein tissue explants from gene-targeted mice are embedded within a three-dimensional, type I collagen matrix. Unexpectedly, neither MMP-2, MMP-9, their cognate cell-surface receptors (i.e., β3 integrin and CD44), nor plasminogen are essential for collagenolytic activity, endothelial cell invasion, or neovessel formation. Instead, the membrane-anchored MMP, MT1-MMP, confers endothelial cells with the ability to express invasive and tubulogenic activity in a collagen-rich milieu, in vitro or in vivo, where it plays an indispensable role in driving neovessel formation.

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