Showing papers on "Transdifferentiation published in 1993"
TL;DR: It is demonstrated that new islet cells are formed continuously from duct cells, underscore the lymphokine's ability to initiate a complex 'transdifferentiation' pathway, providing a window for understanding lineage interrelationships within a terminally differentiated structure.
Abstract: We have identified a model system for the study of pancreatic islet development and regeneration in transgenic mice bearing the interferon-gamma (IFN-g) gene expressed in the pancreatic islets. Previous studies showed that the locally produced IFN-g causes lymphocyte infiltration and islet cell destruction. Here we demonstrate that new islet cells are formed continuously from duct cells as evidenced by (1) the dramatic proliferation of duct cells, (2) the appearance of primitive cells and (3) their subsequent differentiation to endocrine cells. The IFN-g induced islet neogenesis is similar to embryonic islet morphogenesis and offers a model system for studying factors modulating islet development. Additionally, the duct cells occasionally transdifferentiate to gastrointestinal-like cell types and hepatocytes. These results underscore the lymphokine9s ability to initiate a complex ‘transdifferentiation’ pathway, providing a window for understanding lineage interrelationships within a terminally differentiated structure.
349 citations
Journal Article•
TL;DR: The relationship between the corneal-limbal epithelial cells and conjunctival epithelia was analyzed by comparing their growth and differentiation properties in an identical cell culture environment, and fornix cells were found to have a much greater proliferative potential than bulbar and palpebral cells.
Abstract: Purpose The anterior surface of the eye is covered by several physically contiguous but histologically distinguishable epithelial overlying the cornea, limbus, bulbar conjunctiva, fornix conjunctiva, and palpebral conjunctiva. It is important to determine whether the different phenotypes of these epithelia are the result of intrinsic divergence, extrinsic modulation, or a combination of both. Based on keratin expression and cell kinetic criteria, the authors previously suggested that corneal epithelial stem cells may actually reside in the limbal basal layer. Methods In this article, the relationship between the corneal-limbal epithelial cells and conjunctival epithelial cells was analyzed by comparing their growth and differentiation properties in an identical cell culture environment. Results Using Dispase instead of trypsin to dissociate the cells, the authors were able to grow all five rabbit ocular surface epithelia in the presence of 3T3 feeder cells. They found that corneal and limbal cells synthesize identical keratins, including large amounts of the K3 and K12 markers of corneal-type differentiation. By contrast, all three conjunctival epithelia shared another keratin pattern, with large amounts of simple epithelial keratins but only minute amounts of K3/K12 keratins. Conclusions This observation, coupled with previous findings that the "transdifferentiation" of conjunctival epithelial cells to corneal epithelium appears to be both incomplete and reversible, provides strong evidence that (1) the limbal-corneal epithelial cells form a lineage distinct from the conjunctival lineage and (2) conjunctival transdifferentiation actually represents a process of environmental modulation. In addition, of the three types of conjunctival epithelial cells, fornix cells were found to have a much greater proliferative potential than bulbar and palpebral cells. This observation, coupled with recent finding that fornix is enriched in slow-cycling (label-retaining) cells, raises the possibility that conjunctival epithelial stem cells may preferentially reside in the fornix.
222 citations
TL;DR: Results obtained identify TGFβ and TNFα as mediators stimulating key events in liver fibrogenesis (i.e. FSC proliferation, FSC transdifferentiation into MFBIC, and fibronectin synthesis).
Abstract: Transforming growth factor-β (TGFβ1) and tumor necrosis factor alpha (TNFα) stimulate the trans-differentiation of fat-storing cells (FSC) in the rat liver into highly active and “synthetic” myofibroblast-like cells (MFBIC). This activation has been documented by differential-interference contrast and light microscopy using morphologic criteria (a reduction in the number and size of fat droplets, cell flattening and the development of long cytoplasmic extensions), by the loss of retinyl-palmitate (measured by HPLC) and by the enhanced expression of iso-α smooth muscle actin (demonstrated by immunofluorescence microscopy). Furthermore, while cell growth measured by the cell count and DNA content is slightly inhibited by TGFβ1 (0.81 of the control), the combination of TGFβ1 with TNFα stimulates cell proliferation to 1.44 times of the control. In addition the combination of TGFβ and TNFα potentiated the stimulatory effect on fibronectin synthesis (TGFβ alone: 1.4 times control; TNFα alone: 2.2 times control; TGFβ plus TNFα: 4.7 times control). The total protein synthesis was not altered by TGFβ or TNFα. In summary the results obtained identify TGFβ and TNFα as mediators stimulating key events in liver fibrogenesis (i.e. FSC proliferation, FSC transdifferentiation into MFBIC, and fibronectin synthesis).
126 citations
TL;DR: It is found that cultured neural crest-derived cells from embryonic quail peripheral nerves gave rise to melanocytes following treatment with basic fibroblast growth factor (bFGF) or 12-O-tetradecanoyl phorbol-13-acetate (TPA) and that bFGF acts via an intracrine mechanism.
Abstract: We previously found that cultured neural crest-derived cells from embryonic quail peripheral nerves, which consist mostly of Schwann cell precursors, gave rise to melanocytes following treatment with basic fibroblast growth factor (bFGF) or 12-O-tetradecanoyl phorbol-13-acetate (TPA). Here, we show that antisense deoxyoligonucleotides targeted against two regions of the bFGF mRNA transcript blocked this TPA-induced transdifferentiation of Schwann cell precursors. Neither sense nor scrambled antisense control oligonucleotides had any effect in this regard. TPA increased bFGF protein expression in cell lysates but not in conditioned media from these cultures, and this expression was localized to the nucleus and cytoplasm. Furthermore, bFGF-neutralizing antibodies and inositol-hexakisphosphate (InsP6) both inhibited pigmentation caused by exogenous bFGF, but had no affect on TPA-induced melanogenesis, suggesting that bFGF is not released by these cells. These data indicate that bFGF is necessary for the TPA-induced transdifferentiation of Schwann cell precursors into melanocytes and that bFGF acts via an intracrine mechanism.
120 citations
TL;DR: It is raised the distinct possibility that variations in the local production of FGFs and their receptors in the eye during development may, in part, regulate the pathway of differentiation of RPE and neural retina precursors.
Abstract: Publisher Summary This chapter discusses the events of retinal development and the results of early studies on retinal regeneration in vivo . It describes the distribution and biological actions of various growth factors present in ocular tissues. Recent investigations in the chicken embryo that demonstrated for the first time that fibroblast growth factors (FGFs) can induce retinal regeneration in vivo in vertebrates is presented. The possible role of FGFs in retinal-cell differentiation is also discussed. In nearly all adult vertebrates, separation of the retinal pigment epithelium (RPE) and neural retina typically leads to degeneration of the retina and subsequent loss of vision if not surgically corrected. Transdifferentiation is defined as an alteration of the state of differentiation of cells that have already been, at least partially, specialized or programmed in a given direction under normal conditions in situ . In a number of vertebrate species, transdifferentiation of the RPE into neural retina has been demonstrated in situ during retinal regeneration, as well as in transplantation experiments and under tissue-culture conditions.
78 citations
TL;DR: Results indicated that lens transdifferentiation from PECs proceeds through a multipotent (or at least bipotent) intermediate cell state in which the c-myc gene is activated, but neither PEC- nor lens-specific genes are expressed.
Abstract: Retinal pigmented epithelial cells (PECs) of chicken embryos extensively and almost synchronously transdifferentiate into lens cells in medium containing phenylthiourea and testicular hyaluronidase, passing through the bipotent dedifferentiated state. We have isolated genes that are expressed specifically by either pigment or lens cells and analyzed their expression in the transdifferentiation process. The expression of some proto-oncogenes was also studied. In the dedifferentiation process, expression of the c-myc gene was enhanced and the transcription of PEC-specific genes (MMP115, pP344) was completely repressed. However, transcription of lens-specific genes (alpha-, beta- and delta-crystallins genes) remained silent in dedifferentiated pigment cells. Activation of len- or PEC-specific genes occurred only in conditions permissive for lens or PEC differentiation, respectively. These results indicated that lens transdifferentiation from PECs proceeds through a multipotent (or at least bipotent) intermediate cell state in which the c-myc gene is activated, but neither PEC- nor lens-specific genes are expressed.
66 citations
TL;DR: It is suggested that basic FGF must play a major role in enhancing transdifferentiation of pigmented epithelial cells to lens cells.
Abstract: In vitro transdifferentiation of retinal pigmented epithelial cells of the chick embryo into lens cells can be markedly enhanced by culture in the presence of testicular hyaluronidase and phenylthiourea. Since the commercial preparations of hyaluronidase that had previously been used were very crude, a search for the actual effective molecule(s) enhancing lens transdifferentiation was conducted. First, we purified the enzyme and tested the effect of the purified hyaluronidase. Highly purified hyaluronidase itself did not enhance lens transdifferentiation. The crude hyaluronidase was then separated according to affinity with heparin, considering the possibility that the fibroblast growth factor (FGF) is contained in the crude hyaluronidase. Transdifferentiation-enhancing activity was detected in the fraction which was bound to heparin and eluted with 2 M NaCl, where no hyaluronate-degrading activity existed. Analysis of the fraction by SDS-PAGE revealed the existence of an 18 kDa protein whose NH2-terminal sequence was identical to that of basic FGF. The basic FGF derived from bovine brain also enhanced lens transdifferentiation of pigmented epithelial cells. These findings suggest that basic FGF must play a major role in enhancing transdifferentiation of pigmented epithelial cells to lens cells.
61 citations
36 citations
TL;DR: It is concluded that mechanochemical interactions between the muscle cells and their substrate are responsible for both activation and inhibition of DNA replication and transdifferentiation.
30 citations
TL;DR: Evidence that RPE cells from adults can transdifferentiate into neurons under the influence of a specific oncogene is provided, the first report on transdifferentiation of adult human pigment epithelium into a neuronal cell type.
Abstract: The identification of homologs to viral oncogenes in normal cells coupled with development of techniques for DNA transfer into cells offers a powerful approach to dissect the processes associated with differentiation-specific oncogenes. We have derived cell lines by transfection of viral DNAs and proto-oncogenes into primary retinal pigment epithelial (RPE) cells. Establishment of cell lines was successfully achieved with the SV40 large T-antigen gene activated form of Harvey (H)-ras proto-oncogene, c-myc, and adenovirus E1A. The cell lines derived using the H-ras oncogene appeared to contain cells with a neuronal phenotype. This feature was not observed in cell lines established with the other oncogenes. Characteristically, H-ras-transfected cells all exhibited features associated with neurons around 10–14 passages. The transdifferentiated cells were biochemically characterized and found to express neuronal markers, such as neurofilament protein and neuron-specific enolases. The specific neurona...
22 citations
TL;DR: The development of the adult endocrine pancreas was followed throughout metamorphosis in the sea lamprey using electron microscopy and immunocytochemistry and it was discovered that the caudal Pancreas develops from the larval extrahepatic common bile duct through the process of transdifferentiation.
Abstract: The development of the adult endocrine pancreas was followed throughout metamorphosis in the sea lamprey using electron microscopy and immunocytochemistry. It was discovered that the caudal pancreas develops from the larval extrahepatic common bile duct through the process of transdifferentiation (dedifferentiation/redifferentiation). Early in metamorphosis the bile duct epithelial cells possess large vacuoles, resembling autophagic vacuoles, containing recognizable cell material. There is a loss of the large bundles of intermediate filaments characteristic of the larval bile duct epithelium. These same cells are then seen to contain granules immunoreactive for insulin. Pancreatic islets develop within the base of the bile duct epithelium from these transdifferentiated cells and migrate into the surrounding connective tissue to form the caudal pancreas. The cranial pancreas was found to develop from the epithelia lining the developing adult diverticulum and anterior intestine in a similar fashion as those in the larva. The second cell type to appear in either portion of the developing pancreas is similar to the third cell type of the adult: cells immunoreactive for somatostatin do not appear until late in metamorphosis in either region. © 1993 Wiley-Liss Inc.
TL;DR: It has been clarified that the silver gene partially suppresses melanin synthesis in the eyes as well as in the feather follicles, suggesting that the transdifferentiation of RPE into a neural retina would occur following partial suppression of melan in the B I B RPE cells.
Abstract: Homozygotes for silver plumage gene (BIB) of Japanese quail have an abnormal retina, i.e. there is a circular pigment lacking area on the center of retina, therefore, the pigmented part takes a doughnut or ring shape and the character is called a ring retina for convenience sake. This abnormality was studied light-microscopically in comparison with the wild-type (+/ +) and silver heterozygote (Bl +). Transdifferentiation from retinal pigment epithelium (RPE) into neural retina was found to occur at the pigment lacking abnormal area of BIB retina. The abnormality was first observed as a partial thickening at the fundus of RPE in 5-day embryos. It gave rise to the structure of neural retina at about 7-days of incubation and hence, double layer retinas were formed at the fundus. Both original and transdifferentiated neural retinas began to degenerate at about 10 days of incubation. In both B I B and BI + retinas, melanin synthesis was retarded and melanin granules were less abundant as compared with the +/ + retina. In addition, no melanin granules were observed in the choroid of BIB and BI + embryos. Thus, it has been clarified that the silver gene partially suppresses melanin synthesis in the eyes as well as in the feather follicles. These observations suggest that the transdifferentiation of RPE into a neural retina would occur following partial suppression of melanin synthesis in the B I B RPE cells.
TL;DR: The finding of reduced viral replication in terminally differentiated neuronal cells has important implications for understanding the mechanism by which neurotropic viruses are able to establish a long-term persistent infection in the central nervous system in the absence of severe pathological changes.
Abstract: We have investigated the replication of lymphocytic choriomeningitis virus (LCMV) before and after the nerve growth factor (NGF)-induced transdifferentiation of PC12 cells from the chromaffin to the neuron-like phenotype. Untreated and NGF-treated cells were equally susceptible to LCMV infection; however, the viral yield was found to be 1,000-fold lower in NGF-differentiated PC12 cells. The reduced viral yield correlated with restricted LCMV replication and transcription within the infected cell, which was not caused by the lack of cell proliferation in the NGF-treated cells but rather was related to the induction or changes in expression levels of specific gene product(s) associated with the cell commitment to a neuronal phenotype. The return to the chromaffin phenotype after withdrawal of NGF restored normal LCMV yields as well as levels of viral replication and transcription. The finding of reduced viral replication in terminally differentiated neuronal cells has important implications for understanding the mechanism by which neurotropic viruses, such as LCMV, are able to establish a long-term persistent infection in the central nervous system in the absence of severe pathological changes.
Journal Article•
TL;DR: It was shown that the appearance and accumulation of NF-200 take place soon after NR removal, are topologically associated with the areas of RPE and iris conversion, and depend on cell dedifferentiation rate.
Abstract: The presence of the neuronal intermediate filament protein NF-200 in trans-differentiating cells of the retinal pigment epithelium (RPE) and in cells of undifferentiated neural retina (NR) rudiment during eye regeneration in the newt was determined using immunohistochemical methods. It was shown that the appearance and accumulation of NF-200 take place soon after NR removal, are topologically associated with the areas of RPE and iris conversion, and depend on cell dedifferentiation rate. NF-200 distribution in intact and regenerated NR coincides with that described earlier in birds and mammals. Mechanisms controlling transdifferentiation of RPE cells into NR cells are discussed.
TL;DR: This work demonstrates that this molecule has both the ability to attract lymphocytes in vivo as well as to suppress the anti-islet immune response, and this molecule could be relevant for therapeutic intervention in IDDM.
Abstract: We have produced and studied several transgenic models of insulin dependent diabetes mellitus (IDDM). For understanding the etiology of IDDM, we have investigated the consequences of expression of host defense molecules in the pancreatic islets. IFN-γ is produced in response to infection and has immune-stimulatory and proliferative activities. To investigate the potential role of IFN-γ in inflammatory autoimmune diseases, transgenic mice expressing IFN-γ in pancreatic beta cells were created. These mice suffer from islet cell loss following the appearance of increasing numbers of lymphocytes within and surrounding the islets. We have studied the islet destruction in these mice and have demonstrated that it is mediated by inflammatory cells. Interestingly a proliferative/regenerative response opposes the lymphocyte destruction. We have recently been characterizing this proliferative axis in the transgenic pancreas. We have acquired evidence that it is initiated by duct cell proliferation and with the appearance of more primitive neuroendocrine progenitor cells along the apical regions of the ducts. The regenerative process in the ins-IFN-γ transgenic mice appears similar to the events that occur during embryonic islet cell development. These studies underscore the lymphokine's ability to initiate a complex “transdifferentiation” pathway within a terminally differentiated structure. Another fascinating molecule with potential relevance for treatment of IDDM is the cytokine IL-10. This molecule appears to have immuno-inhibitory effects that include the suppression of antigen presentation by macrophages. We have recently investigated the effects of the cytokine IL-10 on the pancreatic islets. These efforts were designed to test whether the expression of IL-10 could allow the creation of neutral islet tissue for allografting. Our work demonstrates that this molecule has both the ability to attract lymphocytes in vivo as well as to suppress the anti-islet immune response. We have utilized several experimental protocols to study the in vivo effects of this molecule. The results of these studies argue that this cytokine could be relevant for therapeutic intervention in IDDM. Our methodologies should clarify the potentially pathogenic capabilities of host defense molecules when expressed in vivo. Additional IDDM models, produced by ourselves as well as our colleagues will be discussed.