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At least 613 records · Page 34Linked to original sources
PubMed2002

Neural cell differentiation from retinal pigment epithelial cells of the newt: an organ culture model for the urodele retinal regeneration.

Transdifferentiation from retinal pigment epithelium (RPE) to neural retina (NR) was studied under a new culture system as an experimental model for newt retinal regeneration. Adult newt RPEs were organ cultured with surrounding connective tissues, such as the choroid and sclera, on a filter membrane. Around day 7 in vitro, lightly pigmented "neuron-like cells" with neuritic processes were found migrating out from the explant onto the filter membrane. Their number gradually increased day by day. BrdU-labeling study showed that RPE cells initiated to proliferate under the culture condition on day 4 in vitro, temporally correlating to the time course of retinal regeneration in vivo. Histological observations of cultured explants showed that proliferating RPE cells did not form the stratified structure typically observed in the NR but they rather migrated out from the explants. Neuronal differentiation was examined by immunohistochemical detection of various neuron-specific proteins; HPC-1 (syntaxin), GABA, serotonin, rhodopsin, and acetylated tubulin. Immunoreactive cells for these proteins always possessed fine and long neurite-like processes. Numerous lightly pigmented cells with neuron-like morphology showed HPC-1 immunoreactivity. Fibroblast growth factor-2 (FGF-2), known as a potent factor for the transdifferentiation of ocular tissues in various vertebrates, substantially increased the numbers of both neuron-like cells and HPC-1-like immunoreactive cells in a dose-dependent manner. These results indicate that our culture method ensures neural differentiation of newt RPE cells in vitro and provides, for the first time, a suitable in vitro experimental model system for studying tissue-intrinsic factors responsible for newt retinal regeneration.

Animals↗
PubMed2006

Genetic analysis of neuroendocrine tumor cells in prostatic carcinoma.

BACKGROUND: Neuroendocrine differentiated tumor cells can be found in the majority of prostatic adenocarcinomas. During antiandrogen or androgen-withdrawal therapy the neuroendocrine differentiation is often increased but its prognostic value is discussed controversially. The origin of neuroendocrine tumor cells is under discussion. While double staining experiments suggest a non-neoplastic pluripotent stem cell, in vitro studies demonstrate a transdifferentiation of exocrine tumor cells to a neuroendocrine phenotype. METHODS: Neuroendocrine differentiated LNCaP cells and laser captured microdissected cells of eight radical prostatectomies were allelotyped using 11 microsatellite markers from seven different loci. RESULTS: Identical allelic profiles were detected in untreated and neuroendocrine differentiated LNCaP cells for all markers confirming their clonality. Neuroendocrine and exocrine tumor cells from radical prostatectomies shared identical allelic profiles for all markers, suggesting a common origin for both cell populations. CONCLUSIONS: Our results support the concept of transdifferentiation of exocrine tumor cells to a neuroendocrine tumor cell phenotype.

Adenocarcinoma↗
PubMed2006

Genistein-induced neuroendocrine differentiation of prostate cancer cells.

BACKGROUND: Neuroendocrine (NE) cells are present in normal prostate and their number appears to be increased in advanced prostate cancer (PCA). In this study, we studied the effect of the phytoestrogen, genistein, on NE differentiation of LNCaP cells in vitro. METHODS: Neuroendocrine marker expression of LNCaP cells exposed to genistein was measured by immunohistochemistry, Western blot, and real-time PCR methods. Western blot analysis was used to study cell cycle and signaling pathways induced by genistein treatment. RESULTS: Six days after continuous genistein treatment, the majority of genistein-surviving cancer cells underwent transdifferentiation into a NE-like phenotype overexpressing the NE markers chromogranin A, synaptophysin, serotonin, and beta-III tubulin. This NE differentiation process was associated with upregulation of the cell cycle modulators p21, p27, and p53, and activation of the MAPK and STAT3 pathways. CONCLUSION: Our data indicate that genistein evokes not only apoptosis but also NE transdifferentiation of PCA cells.

Antineoplastic Agents↗
PubMed2001

Integrin and talin in the jellyfish Podocoryne carnea.

We have isolated an integrin-beta and -alpha subunit from Podocoryne carnea (Cnidaria, Hydrozoa) and studied their expression in the life-cycle and during cell migration, in vitro transdifferentiation and regeneration. Comparison of the integrin expression pattern with a Podocoryne talin homologue by RT-PCR demonstrates that all three genes are maternal messages and continuously expressed in the life-cycle, in medusa development and in all medusae tissues. In situ hybridisation experiments confirm co-expression of both integrin subunits in the different life-stages. Integrin expression was furthermore studied in isolated striated muscle induced to transdifferentiate to new cell types, or grafted on ECM where the muscle adheres and migrates. Integrin expression was maintained continuously throughout both processes. These results suggest that in Podocoryne carnea processes such as cell migration and differentiation are not controlled by up- or downregulation of alternative integrin subunits, but by a single integrin heterodimer which activates different downstream signalling cascades.

Amino Acid Sequence↗
PubMed1994

Responses to cAMP depend on stage of neuronal differentiation of NGF-treated adrenal chromaffin cells.

The nerve growth factor (NGF)-dependent transdifferentiation of adrenal chromaffin cells into sympathetic neurons occurs in two sequential phases: The first phase, in which cells extend neurites and increase proliferation, is mimicked by phorbol myristate acetate (PMA), an activator of protein kinase C. Analogs of cAMP, and forskolin, an activator of adenylate cyclase, antagonize the early effects of both NGF and PMA. The second phase of transdifferentiation, in which cells withdraw from the mitotic cycle and express a true neuronal phenotype, occurs after about 2 weeks of exposure to NGF and is neither mimicked by PMA alone nor antagonized by cAMP. Rather, cAMP promotes the neuronal phenotype of cells previously exposed to NGF or PMA. Thus NGF appears to activate different second messenger systems depending on the stage of differentiation of its target cells.

Animals↗
PubMed1995

The matured eye of Xenopus laevis tadpoles produces factors that elicit a lens-forming response in embryonic ectoderm.

Previous studies have indicated that the outer cornea can undergo transdifferentiation to form a lens in the tadpole larva of Xenopus laevis following removal of the original lens. This transformation appears to require an interaction with the neural retina. In the present study, we carried out a series of experiments to determine if the matured tadpole eye can also elicit lens formation in embryonic ectoderm. Labeled embryonic ectoderm was removed from the presumptive lens-forming region, or from the belly region (ventral ectoderm), at various stages of development (stages 11-19, gastrula to neural tube stages) and implanted into the eye cavity (posterior chamber) of advanced stage 52-55 tadpoles. After 3 days, we examined the tadpoles and their implanted tissues for lens cell formation using lens-specific antibodies. Implanted presumptive lens ectoderm differentiated lens cells in a large number of cases. The percentage of cases forming lens cells and the extent of morphological differentiation increased with increasing age of the implanted tissue. Implanted ventral ectoderm also formed lens cells, although at a reduced frequency and with limited morphological differentiation. These results indicate that the environment of the matured tadpole eye cavity stimulates lens cell formation in both presumptive lens and nonlens ectoderm. The development of the implanted tissues was compared to that found in previous studies where these tissues were cultured as explants or transplanted to lens-forming regions during early development and subjected to various periods of embryonic lens induction. Together, these findings suggest that the process of embryonic lens formation is related to that involved in transdifferentiation of the tadpole cornea during "lens regeneration." However, the inductive effect of the matured tadpole eye is qualitatively different from that of the early period of embryonic lens induction and, while more intense, may be more closely related to that which takes place via the optic vesicle during the later phase of embryonic lens induction.

Animals↗
PubMed2000

Hydra metalloproteinase 1: a secreted astacin metalloproteinase whose apical axis expression is differentially regulated during head regeneration.

The newly emerging astacin metalloproteinase family comprises multiple members with diverse functions. Most recently, the development-related functions have been attributed to both (1) proteolytic cleavage and subsequent release of active TGF-beta-like growth factors from latent inhibitory complexes and (2) modification of extracellular matrix (ECM) assembly and composition. We previously identified and purified hydra metalloproteinase 1 (HMP-1), a developmentally important astacin proteinase that functions in head regeneration and transdifferentiation of tentacle battery cells (L. Yan et al., 1995, Development 121, 1591-1602). In the present study, further cloning revealed that HMP-1 is produced as a secreted zymogen with a conserved hydrophobic signal sequence and a putative propeptide. The processed HMP-1 is composed of a characteristic astacin proteinase domain and a unique Cys-rich C-terminus. With this simple domain structure, HMP-1 represents an ancestral astacin proteinase. Consistent with its role in head regeneration, HMP-1 mRNA is expressed at highest levels by endodermal cells at the apical pole of the body column just inferior to the base of tentacles, the region of active cell differentiation or transdifferentiation. A modified immunocytochemical procedure demonstrated that HMP-1 protein can be localized not only to ECM of tentacles as we previously reported, but also to endodermal cells of the body column in a pattern similar to its mRNA distribution. The localization of HMP-1 protein in tentacles was confirmed using an enzymatic approach. A translocation of HMP-1 protein from cells in the body column to the extracellular milieu in tentacles further suggests that HMP-1 is a secreted protein. HMP-1 expression undergoes extensive regulation at the transcriptional level both temporally and spatially during head regeneration. The involvement of HMP-1 in this morphogenetic process is further supported by the blockage of head regeneration with localized antisense treatment. Taken together, these results suggest that HMP-1 is a secreted astacin metalloproteinase that has an important role in regulating hydra head morphogenesis potentially through its differential expression along the body axis.

Amino Acid Sequence↗
PubMed2003

Pancreatic cancer - a continuing challenge in oncology.

Pancreatic cancer is still one of the major health problems because of its rising incidence and the modest therapeutic results. The paper surveys the statistical data, the risk factors, the preneoplastic ductal lesions, the hormonal sensitivity, the possible transdifferentiation in the endocrine and exocrine parts and the possibilities for chemoprevention. Hungary is peculiar among the European countries because during the last 50 years the incidence of pancreatic cancer has displayed a 15-fold increase. Apart from smoking, additional risk factors seem to be important, and recently a puzzling association between Helicobacter pylori seropositivity and pancreatic cancer was found. First-degree relatives of patients with pancreatic cancer are also at increased risk of this tumor. The term pancreatic intraepithelial neoplasia (PanIN) seems yet to be established, but the dynamics of these lesions needs to be further elucidated. Several lines of firmly established data indicate the hormonal sensitivity of this tumor, but still an unexplained discrepancy exists between the experimental and the clinical results. In addition to the somatostatin analogs, anti-gastrin vaccine is being tested. The mixed exocrine-endocrine tumors might suggest a real possibility of transdifferentiation between different compartments of the pancreas. Finally, the paper outlines the available data about the possibility of chemoprevention, including the role of cyclooxygenase inhibitors.

Hungary↗
PubMed2006

Ectopic expression of neurogenin 3 in neonatal pig pancreatic precursor cells induces (trans)differentiation to functional alpha cells.

AIMS/HYPOTHESIS: Neurogenin 3 (NEUROG3), a basic helix-loop-helix transcription factor that is needed for endocrine cell development in the embryonic pancreas, has been shown to induce transdifferentiation of duct cells from adult pancreas towards a neuro-endocrine phenotype. Our study explored the endocrine transdifferentiation potential of NEUROG3 in neonatal pancreatic precursor cells. MATERIALS AND METHODS: A replication-deficient adenovirus expressing Neurog3 and green fluorescent protein (GFP) (Ad-NEUROG3) was used to infect neonatal pig pancreatic cell preparations enriched for endocrine islet and cytokeratin-positive precursor cells. GFP-positive cells were sorted using flow cytometry on days 3 and 8 after infection and characterised at the transcript and protein level. For in vivo experiments, the total population of Ad-NEUROG3-infected pancreatic cells was transplanted, then later removed for determination of graft hormone content and immunohistochemistry. RESULTS: Among the GFP-positive cells, the fraction of precursor cells decreased by more than 85% at day 8 after infection, while the fraction of glucagon-positive cells increased 2.5-fold and the beta cell number remained the same. Transplantation of the Ad-NEUROG3-infected pancreatic cell preparation failed to reverse streptozotocin-induced hyperglycaemia, while non-infected cells and a control cell preparation infected with replication-deficient adenovirus expressing only GFP were able to do so. At day 109 after transplantation, kidneys grafted with Ad-NEUROG3-infected pancreatic cells contained significantly decreased insulin and increased glucagon levels. Abundant glucagon-immunopositive cells were seen in Ad-NEUROG3-infected grafts, which were virtually devoid of proliferating insulin-positive cells. CONCLUSIONS/INTERPRETATION: In summary, adenoviral delivery of NEUROG3 to pancreatic precursor cells from neonatal pig pancreas promotes alpha cell differentiation in vitro and in vivo.

Adenoviridae↗
PubMed2005

Transplantation of human umbilical vein endothelial cells improves left ventricular function in a rat model of myocardial infarction.

INTRODUCTION: Although cell-based therapy after myocardial infarction (MI) may be beneficial in improving cardiac dysfunction, the underlying mechanisms remain to be clarified. Since human umbilical vein endothelial cells (HUVEC) harbor the potential for transdifferentiation, we studied the functional effects of HUVEC transplantation in a rat model of MI. METHODS AND RESULTS: HUVEC labeled with BrdU or medium alone were injected into the infarcted area and its margin 4 weeks after ligation of the left coronary artery in cyclosporine-treated rats. BrdU(+) signals could be detected in the area of MI at two weeks and two months after injection only in hearts transplanted with HUVEC. While no signs of transdifferentiation into cardiomyocytes were evident, staining for the rat macrophage marker ED-1, adjacent to or colocalized with BrdU(+) signals, revealed an in.ltration with macrophages and implied the phagocytosis of injected HUVEC. In the vicinity of BrdU(+) signals, the density of CD31(+) microvessels was significantly increased in HUVEC-transplanted as compared to medium-treated hearts after two months. HUVEC transplantation led to improved contractility as assessed by echocardiography and to higher coronary flow rates as well as to improved response to volume strain and catecholamine stress in Langendorff perfused hearts. CONCLUSIONS: After MI, transplanted HUVEC persist in the host myocardium and trigger an infiltration with macrophages. The ensuing increase in neovascularization and improvement in global left ventricular function may be attributable to the associated inflammatory response.

Animals↗
PubMed2003

Analysis of the TP53 gene in laser-microdissected glioblastoma vasculature.

Malignant transformation of human gliomas is accompanied by extensive proliferation of stromal blood vessels. Recent data suggest mesenchymal transdifferentiation of neoplastic cells in various human cancers, including colon and breast cancer as well as gliosarcoma. In this study, we have analyzed proliferating stromal blood vessels in glioblastoma multiforme for the presence of mutations in the tumor suppressor gene TP53. Using tissue arrays derived from glioblastoma specimens, cases with significant immunohistochemical p53 accumulation were selected for molecular genetic detection of TP53 mutations in exons 5 to 8. None of the tumors included in this series displayed properties of gliosarcoma. Proliferating glomeruloid stromal vessels were isolated by laser microdissection from paraffin sections. In six cases, single-strand conformation polymorphism analysis for mutations of the TP53 gene in stromal blood vessels compared with adjacent tumor cells and subsequent DNA sequencing of the resulting DNA fragments were carried out. Glioblastoma cells of these cases exhibited TP53 mutations in exons 5, 7 and 8. None of these tumors showed TP53 mutations in microdissected samples from glomeruloid vessels. The absence of TP53 mutations in vascular stromal components of glioblastoma multiforme supports the hypothesis that microvascular proliferations originate from the tumor stroma and are not derived from transdifferentiated glioblastoma cells.

Cell Differentiation↗
PubMed2005

Independent differentiation of mammotropes and somatotropes in the chicken embryonic pituitary gland. Analysis by cell distribution and attempt to detect somatomammotropes.

It has been reported that mammotropes in a rodent pituitary gland are derived from somatotropes via somatomammotropes (SMTs), cells that produce both growth hormone (GH) and prolactin (Prl). However, no studies have been done on the transdifferentiation of somatotropes in the chicken pituitary gland. In this study, in order to determine the origin of mammotropes, we studied detail property of appearance of chicken somatotropes, mammotropes and pit-1 cells and then evaluated the existence of SMTs in the chicken embryonic pituitary gland. Immunohistochemical analysis revealed that GH-immunopositive (GH-ip) cells appeared on embryonic day (E) 14 and were mainly distributed in the caudal lobe, while Prl-immunopositive (Prl-ip) cells appeared in the cephalic lobe of the pituitary gland on E16. In situ hybridization (ISH) and RT-PCR analysis showed that expression of GH and Prl mRNA starts at E12 in the caudal lobe and at E14 in the cephalic lobe respectively. Pit-1 mRNA was first detected on E5 by RT-PCR, and pit-1 mRNA-expressing cells were found in the cephalic lobe on E8. Then with the ontogeny of the chicken, these cells spread into both lobes. Using a double staining method with ISH and immunohistochemistry, we could not detect the existence of SMTs in the chicken embryonic pituitary gland even in the marginal region of either lobe. These results suggest that chicken somatotropes and mammotropes independently appear in different lobes of pituitary gland and that transdifferentiation from somatotropes to mammotropes is not the central route for differentiation of mammotropes in the embryonic chicken pituitary gland.

Animals↗
PubMed1998

Expression and function of a retinoic acid receptor in budding ascidians.

Retinoic acid is thought to induce transdifferentiation of multipotent epithelial stem cells in the developing buds of the ascidian Polyandrocarpa misakiensis. We isolated a cDNA clone from this species, named PmRAR, encoding a retinoic acid receptor (RAR) homologue. PmRAR clusters with other RARs on phylogenetic trees constructed by three different methods. Within the cluster, PmRAR is on a separate branch from all the subtypes of RARs, suggesting that RAR subtypes arose in the ancestral vertebrates after divergence of vertebrates and urochordates. The embryos of another ascidian species Ciona intestinalis were co-electroporated with a mixture of a PmRAR expression vector and a lacZ reporter plasmid containing vertebrate-type retinoic acid response elements. The expression of lacZ depended on the presence of both retinoic acid and PmRAR, suggesting that PmRAR is a functional receptor. PmRAR mRNA is expressed in the epidermis and mesenchyme cells of the Polyandrocarpa developing bud. The mRNA is not detectable in the mesenchyme cells in the adult body wall, but its expression can be induced by retinoic acid in vitro. These results suggest that the PmRAR is a mediator of retinoic acid signalling in transdifferentiation during asexual reproduction of protochordates.

Amino Acid Sequence↗
PubMed2006

Fibronectin and laminin induce expression of islet cell markers in hepatic oval cells in culture.

Hepatic oval cells (OC) are considered to be facultative liver stem cells and, because they may undergo differentiation into a variety of cell lineages, they might have the potential to be used in cellular therapy. Signals delivered by extracellular matrix (ECM) proteins take part in cellular differentiation in cooperation with signals from growth factors; indeed, some ECM proteins, such as laminin (LAM) and fibronectin (FN), have been shown to contribute to beta-cell differentiation and islet development, respectively. Since no previous studies have investigated the effect of ECM proteins on the expression of islet cell markers by cultured OC, the purpose of the present study was to evaluate whether FN and LAM modulate the expression of genes related to the endocrine pancreas in these liver cells. OC proliferation was induced in Wistar rats by prolonged treatment with 2-acetoaminofluorene/allyl alcohol and confirmed by reverse transcription/polymerase chain reaction and hepatic immunocytochemical and histopathological analyses. OC isolation was performed by Ficoll gradient and magnetic-activated cell sorting. OC were cultured for 1 and 2 months under several conditions with specific growth factors, over a FN or LAM substrate or in high glucose, nicotinamide and fetal calf serum. OC cultured on FN substrate expressed Pdx-1, Pax-6, insulin 2 and glucagon. LAM also induced the expression of Pdx-1, insulin 1 and insulin 2, glucagon, somatostatin and GLUT-2. Our results suggest that these ECM proteins can be used in protocols of OC transdifferentiation aimed at reducing the period necessary for complete transdifferentiation.

2-Acetylaminofluorene↗
PubMed2005

Differential expression of a V-type ATPase C subunit gene, Atp6v1c2, during culture of rat lung type II pneumocytes.

The lung alveolar epithelium consists of type I and type II pneumocytes. In vivo, the type II cell is the progenitor cell from which the type I cell originates. When freshly-isolated type II cells are cultured under conventional conditions they rapidly lose their phenotypic properties and attain characteristics of type I cells. Taking advantage of this transdifferentiation, we sought to identify genes that are differentially expressed during culture of rat type II cells. Using suppression subtractive hybridization (SSH), a vacuolar-type H+-ATPase (V-ATPase) C2 subunit gene (Atp6v1c2) was found to be enriched in freshly isolated rat type II cells compared to those cultured for 4 days. Northern blotting and reverse-transcription polymerase chain reaction (RT-PCR) confirmed the differential expression of Atp6v1c2 during in vitro culture of isolated type II cells. Expression ofAtp6v1c2 was significantly reduced early during in vitro culture: almost 90% reduction was observed after 24 h of incubation as determined by real-time PCR. In situ hybridization showed that Atp6v1c2 is expressed in both bronchiolar and alveolar lung epithelial cells, an expression pattern similar to that of surfactant protein B (SP-B). Multi-tissue Northern blotting revealed a unique tissue distribution with Atp6v1c2 expression limited to lung, kidney and testis. The presence and expression of Atp6v1c2 gene transcript isoforms, resulting from alternative splicing, were also investigated. Elucidation of differential expression of Atp6v1c2 in type II cells and further studies of its regulation may provide information useful in understanding the molecular mechanism underlying phenotypic and functional changes during transdifferentiation of alveolar epithelial cells.

Alternative Splicing↗
PubMed1989

Chromatin structure as a molecular marker of cell lineage and developmental potential in neural crest-derived chromaffin cells.

Adrenal medullary chromaffin cells have the capacity to transdifferentiate into sympathetic neurons. We show here that SCG10, a neural-specific gene that is induced during this transdifferentiation, is maintained in mature chromaffin cells in a potentially active chromatin conformation marked by two DNAase I hypersensitive sites (HSS). A low level of transcription is associated with this conformation. The HSS are also present in neurons expressing high levels of SCG10, but not in nonneuronal cells. Experiments using transgenic mice suggest that these HSS can in principle form in any cell type expressing the gene, but that a cis-repression mechanism normally prevents their assembly in nonneuronal cells. We suggest that the SCG10 HSS may represent a molecular marker of the lineage and phenotypic plasticity of chromaffin cells.

Adrenal Glands↗
PubMedDate not supplied

Ageing in the chick lens: in vitro studies.

In principle, ageing may be due to the interaction of several factors, including the accumulation of random changes both genomic and non-genomic, secondary changes in a tissue contingent upon the changing function of other tissues, and programmed non-random changes in the tissue-specific expression of various genes. The use of a single tissue comprising one cell type only, in which the major gene products are well defined, in which there is a well attested series of developmental and age-related changes in cell properties and gene expression and which can be studied and compared in vivo and in vitro, offers advantages for investigation of these questions. The vertebrate eye lens possesses these advantages. The crystallins (proteins expressed at super-abundant levels in the lens) are well characterised. The lens epithelial cells (LEC) grow readily and can differentiate into the lens fibre cells in vitro, and, finally, such terminally differentiated cells may also be derived, by a process of transdifferentiation, from neural retina cells (NRC) in vitro. Thus the effect on ageing changes of the tissue of origin may also be studied. This article reviews our previous studies on long-term changes in growth potential, differentiation capacity and crystallin expression of chick lens cells in ageing cultures, their overall similarity to events in vivo and the effect on ageing changes of genotypes affecting the growth rate. It presents new information on these genetic aspects, and on crystallin expression in long-term ageing cultures of transdifferentiated neural retina, and compares the behaviour of ageing chick lens cells with that reported for mammals.

Animals↗
PubMed1990

Stimulatory effects of retinal extract and fibroblast growth factor on lentoidogenesis in cultures of chick embryo neuroretinal cells.

A crude extract prepared from embryonic chick retina stimulates growth and particularly transdifferentiation into lens when added as a supplement to neuroretinal (NR) cultures in vitro. This effect is especially marked when using a medium (H) containing 5% horse serum, where growth factors are likely to be limiting. The level of delta-crystallin (lens marker) production in such cultures increases with the concentration of extract. Using extracts from earlier and later stages of retinal development, there is an age-dependent decline in the extent to which transdifferentiation is stimulated. However, such extracts have little effect on the activity of CAT, a neuronal marker enzyme. These effects are most probably mediated by growth factors present in the retinal extract acting upon Müller glial cells or their precursors in the NR cultures. In support of this suggestion, we show that purified fibroblast growth factor (but not epidermal growth factor) exerts similar effects on both culture growth and delta-crystallin accumulation.

Age Factors↗