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PubMed1998

Transdifferentiation of chick embryonic retinal pigment epithelial cells to lentoid structure in suspension culture.

To test transdifferentiation of retinal pigment epithelial (RPE) cells in suspension culture, chick embryonic RPE sheets and dissociated RPE cells were cultured for two months in a non-adherent dish for suspension culture. RPE cells, isolated as a sheet, aggregated immediately and remained the same size with their differentiated characteristics for two months. The presence of basic fibroblast growth factor (bFGF) at concentrations of 10 ng/ml or higher induced the formation of a spherical lentoid structure which was positive for crystallin and bFGF receptor. In contrast, dissociated RPE cells did reaggregate but did not develop the lentoid structure even in the presence of bFGF. The transdifferentiation of RPE cells to the lentoid structure in this study was in contrast to their transdifferentiation to the retina, as reported in a previous study.

Animals↗
PubMed2002

Gastrin stimulates beta-cell neogenesis and increases islet mass from transdifferentiated but not from normal exocrine pancreas tissue.

It is still unclear which factors regulate pancreatic regeneration and beta-cell neogenesis and which precursor cells are involved. We evaluated the role of intravenously infused gastrin in regenerating pancreas of duct-ligated rats. The ligation of exocrine ducts draining the splenic half of the pancreas resulted in acinoductal transdifferentiation within the ligated part but not in the unligated part. We found that infusion of gastrin from day 7 to 10 postligation resulted in a doubling of the beta-cell mass in the ligated part as measured by morphometry. This increase in insulin-expressing cells was not associated with increased proliferation, hypertrophy, or reduced cell death of the beta-cells. Furthermore, we found an increased percentage of single, extra-insular beta-cells and small beta-cell clusters induced by gastrin infusion. These changes occurred only in the ligated part of the pancreas, where transdifferentiation of the exocrine acinar cells to ductlike cells (metaplasia) had occurred, and was not found in the normal unaffected pancreatic tissue. In conclusion, we demonstrate that administration of gastrin stimulates beta-cell neogenesis and expansion of the beta-cell mass from transdifferentiated exocrine pancreas.

Animals↗
PubMed2000

Myocyte transdifferentiation: a possible pathogenetic mechanism for arrhythmogenic right ventricular cardiomyopathy.

Adipose substitution of ventricular myocardium is characteristic of arrhythmogenic right ventricular cardiomyopathy, but is also found in other heart conditions. It is thought to be a consequence of myocyte loss due to myocarditis or other noxious stimuli. We describe a unique case of cardiomyopathy with a morphologic pattern suggestive of transdifferentiation from myocytes to mature adipocytes. Gross, histologic, and ultrastructural examination were performed on the heart of a female transplant patient with a clinical diagnosis of familial dilated cardiomyopathy. Gross examination showed fibroadipose substitution of the left ventricle and adipose replacement of the right. Histology, immunohistochemistry, and ultrastructure were highly suggestive of transdifferentiation from cardiac muscle to adipose tissue. Myocyte transdifferentiation could represent an alternative pathogenetic pathway to the myocyte-loss and adipose-replacement mechanism in arrhythmogenic right ventricular cardiomyopathy, or it could be the basis of a new type of familial cardiomyopathy.

Adipocytes↗
PubMed1999

Transdifferentiation of prostate cancer cells to a neuroendocrine cell phenotype in vitro and in vivo.

PURPOSE: To better understand the source of neuroendocrine cells associated with human prostate cancer progression, we studied the ability of a cultured prostate cancer cell line, LNCaP, to transdifferentiate into neuroendocrine-like cells in vitro and in vivo. MATERIALS AND METHODS: Cyclic AMP concentrations were measured in extracts of LNCaP cells cultured in the presence of normal or hormone-deficient medium (containing charcoal-stripped serum) with the use of an immunoassay. Quantitative RT-PCR procedures were used to determine whether hormone depletion affects TGF-beta2 mRNA expression. Western blotting procedures (for neuron specific enolase [NSE]) were used to determine whether TGF-beta2 supplementation or antibody neutralization might affect the ability of cultured LNCaP cells to transdifferentiate to neuroendocrine-like cells. Finally, tumors formed from LNCaP cells xenografted into male nude mice were evaluated for the presence of neuroendocrine cells (prior and subsequent to castration of the host mouse) using an immunohistochemical stain for chromogranin A. RESULTS: LNCaP cells cultured in a hormone-deficient medium have a mean 9-fold increase in cyclic AMP (p = 0.02) and a significant decline in the expression of TGF-beta2 mRNA when compared with cells grown in normal medium. Supplementation or depletion of TGF-beta2 did not affect the neuroendocrine conversion of LNCaP cells as assessed by NSE expression patterns. LNCaP tumors growing in castrated male nude mice were found to have significantly increased numbers of chromogranin A positive neuroendocrine cells (46/high powered field) when compared with tumors growing in intact male mice (3/high powered field) (p = 0.0038). CONCLUSIONS: Exposure of LNCaP cells to a hormone deficient medium drastically increased cyclic AMP production and this may identify the biochemical pathway through which hormone depletion induces a neuroendocrine conversion of prostate cancer cells. Hormone depletion also reduced TGF-beta2 mRNA expression and this finding was consistent with our inability to demonstrate any effect of TGF-beta2 on neuroendocrine conversion in vitro. Finally, our demonstration of increased neuroendocrine cells found in LNCaP tumors growing in castrated immunodeficient mice suggests that the neuroendocrine cells associated with advanced human prostate tumors in vivo, arise from prostate cancer cells through the transdifferentiation process.

Animals↗
PubMed2002

TGF-beta2-induced matrix modification and cell transdifferentiation in the human lens capsular bag.

PURPOSE: To study the role of TGF-beta2 in posterior capsule opacification (PCO) and to determine whether CAT-152 (lerdelimumab), a fully human monoclonal antibody that neutralizes the effect of TGF-beta2, can also provide therapeutic benefit for PCO. METHODS: In vitro capsular bags were prepared from human donor eyes and maintained in a 5% CO(2) atmosphere at 35 degrees C. To investigate expression of active TGF-beta2, capsular bags were incubated in serum-free EMEM for 2, 28, or more than 100 days and analyzed by ELISA (n > or = 4 at each time point). To study underlying mechanisms, match-pair experiments were also performed, so that the medium was supplemented with 0, 1 or 10 ng/mL TGF-beta2 with or without 10 microg/mL CAT-152 (n = 4 in all cases). On-going observations were by phase-contrast microscopy. In addition, donor material from patients who had undergone cataract surgery was analyzed. Cellular architecture was examined by fluorescence cytochemistry. Expression of matrix metalloproteinase (MMP)-2 and -9 was assessed by gelatin zymography. RESULTS: Analysis of capsular bags from donor eyes that had received an intraocular lens (IOL) revealed the presence of endogenous active TGF-beta2, matrix wrinkling, and expression of transdifferentiation markers alphaSMA and fibronectin. When cultured in vitro, donor bags also showed sustained release of MMP-2 and -9. Culture of capsular bags prepared in vitro from whole lenses showed that TGF-beta2 (1-10 ng/mL) stimulated transdifferentiation and contraction of the capsular bag, resulting in light scatter. TGF-beta2 also induced sustained release of MMP-2 and -9. Active TGF-beta2 was detected in these cultures. The human monoclonal anti-TGF-beta2 antibody CAT-152 (10 microg/mL) effectively inhibited all TGF-beta2-induced effects. CONCLUSIONS: Addition of TGF-beta2 accelerates transdifferentiation and contraction of the capsular bag, resulting in light scatter. CAT-152 inhibited all the effects of TGF-beta2 that were examined and therefore has the potential to suppress development of PCO and provide potential therapeutic benefit to cataract patients.

Actins↗
PubMed2003

Evidence for transdifferentiation of human bone marrow-derived stem cells: recent progress and controversies.

Adult bone marrow-derived stem cells have traditionally been known as tissue-specific stem cells capable of producing blood cells. This concept is being challenged by a series of recent discoveries. It has been demonstrated that there are heterogeneous stem cell populations in adult bone marrow compartment. Under appropriate experimental conditions, a certain type of bone marrow stem cells appears to differentiate (or transdifferentiate) into a variety of non-haemopoietic cells of ectodermal, mesodermal and endodermal origins (such as myocytes, neural cells and hepatocytes). The plasticity, that is, the ability to regenerate cells belonging to different organs and tissues of adult (postnatal) stem cells, has raised the therapeutic possibility of using these stem cells for tissue repair and regeneration. Presently, definitive evidence for plasticity or transdifferentiation of bone marrow stem cells is lacking. Despite controversies concerning the plasticity of bone marrow-derived stem cells, early clinical trials are being conducted in patients suffering from myocardial infarct, arthritic and neurological diseases using autologous bone marrow stem cells. This review summarises recent progresses and controversies in transdifferentiation of adult bone marrow-derived stem cells to non-haemopoietic tissues.

Adult↗
PubMed2003

Further evidence of hepatic transdifferentiation in hepatoid adenocarcinomas of the stomach: quantitative analysis of mRNA for albumin and hepatocyte nuclear factor-4alpha.

AIMS: To assess the production of a liver-specific protein, albumin, and of a master transcriptional factor, hepatocyte nuclear factor (HNF)-4alpha, in hepatoid adenocarcinoma tissue. METHODS: Standard and quantitative RT-PCR, using five cases of hepatoid and three cases of non-hepatoid gastric adenocarcinoma. RESULTS: Hepatoid adenocarcinomas expressed similarly large amounts of albumin mRNA as those expressed in hepatocellular carcinoma and normal liver tissues. The observed amounts were several hundred times more than those in non-hepatoid adenocarcinoma and normal stomach tissues. HNF-4alpha mRNA was expressed in all stomach samples examined, and the levels of expression did not quantitatively differ between hepatoid and non-hepatoid adenocarcinomas of the stomach. CONCLUSIONS: These results provide further support of a relationship between hepatic transdifferentiation in hepatoid adenocarcinomas and albumin mRNA expression. Furthermore, transdifferentiation to the hepatocytic phenotype in hepatoid adenocarcinoma tissue was not directly associated with HNF-4alpha expression, thus suggesting that transdifferentiation proceeds by a complicated mechanism.

Adenocarcinoma↗
PubMed2003

[Interleukin-1beta-induced transdifferentiation of renal proximal tubular cells is mediated by p38 mitogen-activated protein kinase phosphorylation].

OBJECTIVE: To investigate the role of p38MAPK signaling pathway in interleukin (IL)-1beta induced transdifferentiation and its functional influences in human renal proximal tubular cell line HK-2 cells. METHODS: Human renal proximal tubular cells, cell line HK-2, were cultured and then co-incubated with IL-1beta (10 ng/ml) for 24 hours. The expression and distribution of cytokeratin and alpha-smooth muscle actin (SMA), markers of transdifferentiation of renal proximal tubular cells, were detected by immunofluorescence staining and confocal microscopy. Western blot technique was used to detect the expression of alpha-SMA 2, 4, 6, 12, 24, and 48 hours after IL-1beta stimulation. The morphology of cells was monitored from the 1st to the 5th day. Expression of alpha-SMA, phosphorylation of p38MAPK was assayed by western blot. Specific p38MAPK inhibitor SB203580 was added into the culture of HK-2 cells, 24 hours later IL-1beta was added for 24 hours Cell-cell adhesion and migration assay were performed. Inverted microscopy was used to examine the morphology of cells after stimulation of IL-1beta for 24 hours. Western blot technique was used to detected total and phosphorylated p38MAPK after stimulation of IL-1beta for 2, 5, 15, 30, 60 and 120 min. RESULTS: The phosphorylation of p38MAPK was increased after treatment of IL-1beta, and reached the level of 1.7 times the basic level 5 - 30 minutes after stimulation (P < 0.05). Almost no expression of alpha-SMA was shown in the control group. Two hours after IL-1beta stimulation, the expression of alpha-SMA was increased a little followed by an up-regulated expression of alpha-SMA 6 to 48 hours after the stimulation. The expression of alpha-SMA was down-regulated by 40% in the SB203580 group in comparison with that in the control (P < 0.01) and by 50% in comparison with that in the IL-1beta group (P < 0.001). The cell number was not significantly different between the IL-1beta group and control group (P > 0.05). A decreased expression of cytokeratin and disordered distribution of alpha-SMA were shown in the cells 24 hours after stimulation of IL-1beta. The morphology of cells remained unchanged 1 to 5 days after IL-1beta stimulation. The cell-cell adhesion was almost identical in the groups with IL-1beta and/or SB203580 no in comparison with that in the control group (P > 0.05). The migration ability of HK-2 cells was 2.2 times that in the control group in the IL-1beta group (P < 0.05) and decreased by 35% in the SB203580 group (P < 0.01). SB203580 uppercased the IL-1beta-induced expression of alpha-SMA and the enhancement of cell migration ability were suppressed by 51% (P < 0.05). CONCLUSION: IL-1beta induces transdifferentiation of renal proximal tubular cells characterized by alpha-SMA expression and enhanced ability of cell migration. These effects are mediated, at least in part, through the activation of p38 MAPK signaling pathway.

Actins↗
PubMed2004

[Relationship between epithelial-immunologic cells transdifferentiation and pseudoepitheliomatous granuloma lesion].

OBJECTIVE: Inappropriate treatment at early stage of wound could result in the formation of pseudoepitheliomatous granuloma (PEG). The correlation of abnormal transdifferentiation of epithelial cells to immunologic cells and the occurrence of PEG lesion was investigated. METHODS: Morphological change of epithelial tissue was observed with histopathology in 11 specimens of PEG lesions and 6 specimens of normal skins from PEG edge (PEG-N) from 11 patients with damaged skin. The expression characteristics and distribution of pan-cytokeratin (CKp), IV type collagen, laminin (LM), epithelial cadherin (E-Cad), beta-catenin (beta-Cat), focal adhesion kinase (FAK), stem cell factor (SCF) and its receptor-c-Kit, proliferating cell nuclear antigen(PCNA), and cluster of differentiation-14 (CD14), CD68 and mast cell tryptase (MCT) in PEG were detected with the immunohistochemical and the indirect immunofluorescent double-staining. RESULTS: In comparison with PEG-N, epithelial tissue take on squamous metaplasia, and stroma was infiltrated with intensive microvessels and inflammatory cells in the PEG lesion. Poor epithelial basal layer constitution, basal polarization, and migration of basal cells to stroma could be observed. In the ultrastructure, the loose intercellular junction of basal cells and the increased nucleus/cytoplasm ratio and intercellular space could be observed, neonatal monocytoid cells and macrophages and mast cells as a exuviate-like manner brooded from cytoplasm of original epithelial cells and basement membrane. protein expression of CKp and E-Cad by basal cells was significantly decreased, and the IV type collagen and LM protein could not be found in basement membrane of identical locus. By contrast, the immunoreactivity of beta-Cat and FAK was apparently increased. In addition, CD14(+) monocytes, CD68(+) macrophages, MCT(+) mast cells and CD68(+)/MCT(+) cells with various size, and these cells of stronger immuno-staining of SCF, c-Kit and PCNA antigen could be found in epithelial tissue and stroma. CONCLUSION: Epithelial cells in PEG related to wound are characteristized by transdifferentiation of epithelial cells to immunologic cells, wich may be associated with local infectious and inflammatory reaction, ultimately resulting in enhancement the ratio of beta-Cat/E-Cad signal and activation SCF-c-Kit signal pathway. The phenomena of transdifferentiation epithelial cells in the PEG lesion will help to recognize of the neoplatic immune and trauma repair mechanism.

Adolescent↗
PubMed2004

[Effect of BMP-7 on the transdifferentiation of cultured human tubular epithelial cell induced by TGF-beta1].

OBJECTIVE: To observe the effect of bone morphogenetic protein-7 (BMP-7) on the transdifferentiation of cultured human tubular epithelial cell (HKC) induced by TGF-beta1 and to elucidate its possible mechanism. METHODS: The cultured HKC cells were divided into 5 groups: serum-free group (negative control); single TGF-beta1 treated group (positive control); single BMP-7 treated group; combined TGF-beta1 and BMP-7 treated group; and BMP-7 pre-treated group. Expression of keratin of HKC cells was assessed by indirect enzyme immunohistochemistry (IEI), expression of alpha-smooth muscle actin (alpha-SMA) and E-cadherin by immunohistological method, percentage of alpha-SMA positive HKC cells by flow cytometry, and mRNA expression of alpha-SMA, TGF-beta1, and TGF-beta type II receptor by reverse transcription PCR. RESULTS: The expression of alpha-SMA and the percentage of alpha-SMA positive HKC cells markedly increased after having been treated by TGF-beta1 while the expression of E-cadherin and keratin decreased. In the group pre-treated with BMP-7 (50 ng/ml) and then added with TGF-beta1 (8 ng/ml), expression of alpha-SMA was significantly lower than in the positive control group, while expression of E-cadherin and keratin significantly higher than in the positive control group. Measurement of the percentage of alpha-SMA positive HKC found significant deference between the combined TGF-beta1 and BMP-7 treated group and the positive control group (9.7% vs 19.8%; 5.8% vs 19.8%; P < 0.05). Significant difference existed between the BMP-7 (50 ng/ml) pre-treated group and the positive control group (8.7% vs 19.8%, P < 0.05). mRNA expression of alpha-SMA was measured by RT-PCR and the results showed that it significantly decreased in the group treated or pre-treated with BMP-7 (50 ng/ml) (15% and 12% of the results in the positive control group, respectively). The mRNA expression levels of both TGF-beta1 and its type II receptor significantly decreased (28% and 19%; 47% and 36%, compared with the positive control group, respectively). CONCLUSION: Transdifferentiation of cultured renal epithelial cell induced by TGF-beta1 can be inhibittd by certain levels of BMP-7, cultured together with TGF-beta1 or pretreated. BMP-7 can prevent and inhibit the mRNA expression of TGF-beta1 and its type II receptor, which may be an important mechanism by which BMP-7 inhibit the transdifferentiation of renal tubular epithelial cell.

Actins↗
PubMed2004

[Effect of total saponins of Panax notoginseng on transdifferentiation of rats' tubular epithelial cell induced by IL-1alpha].

OBJECTIVE: To study whether total saponins of Panax notoginseng (PNS) can prevent renal interstitial fibrosis occurrence through blocking the IL-1alpha induced tubular epithelial cell and decrease the secretion of extracellular matrix (ECM). METHODS: Normal rats' tubular epithelial cells NRK52E were cultured in vitro, their morphological changes were observed by inverted phase contrast microscope and scanning electron microscope. Flow cytometry technique and immuno-histochemical method was used to detect the expression of alpha-smooth muscle actin (alpha-SMA), and ELISA was used to quantitatively detect the fibronectin (FN) in the supernatant RESULTS: IL-1alpha could induce the transdifferentiation of tubular epithelial myofibroblast, showing hypertrophy of cells elongated and fusiform-shaped, with significantly enhanced expression of alpha-SMA and increased secretion of FN (P<0.05). After adding PNS of different concentrations, the morphology of cells restored close to normal tubular epithelial cells, with the increase of alpha-SMA expression and FN secretion significantly inhibited (P<0.05) in dose-dependent manner (P<0.05). But addition of different dosages of PNS alone showed no effect on tubular cells. CONCLUSION: IL-1alpha could induce the transdifferentiation of tubular epithelial myofibroblast, promote the deposition of ECM component FN. PNS could inhibit IL-1alpha induced the transdifferentiation of NRK52E and secretion of ECM, therefore, PNS could be taken as a new drug for prevention and treatment of renal interstitial fibrosis and terminal stage of renal diseases.

Actins↗
PubMed2004

[Effects of hepatectomized rat serum on the transdifferentiation of adult rat bone marrow cells into hepatocyte-like cells].

OBJECTIVES: To study the effects of hepatectomized rat serum and hepatocyte growth factor (HGF) on the transdifferentiation of adult rat bone marrow stem cells (ABMSCs) into hepatic parenchymal cells. METHODS: The serum was collected from the rats 24 hours after being subjected to subtotal hepatectomy. ABMSCs were collected and cultured in DMEM/F12 (1:1) containing the hepaetectomized rat serum or HGF. The differentiated hepatocyte-like cells were labeled with CM-DiI and administrated by tail vein injection into the isogeneic rats. The cultured and injected cells were both identified by immunocytochemistry and cultured cells were assayed using RT-PCR and Western blot. RESULTS: Hepatectomized rat serum and HGF were demonstrated to have the effect of inducing transdifferentiation of ABMSCs into hepatocyte-like cells in vitro. The differentiated cells expressed albumin mRNA and albumin after 7 days++'s co-incubation. Albumin-expressing and CM-DiI positive hepatocyte-like cells were characterized in livers and spleens of the rats injected with the cultivated cells. CONCLUSION: ABMSCs could transdifferentiate into hepatic parenchymal cells by hepatectomized rat serum or HGF.

Animals↗
PubMed2005

[In vitro transdifferentiation of adult human retinal pigment epithelium cells to neuro-like cells induced by blocking VEGF expression].

OBJECTIVE: To investigate the effects of blocking VEGF expression on the retinal pigment epithelium (RPE) in vitro. METHODS: RPE was transfected with plasmid encoding anti-sense of VEGF by lipofectin. RPE clones with stable expression of anti-sense of VEGF were screened by neomycin (G418). The changes of RPE and the level of VEGF secreted by RPE were observed by immunofluorescence immunohistochemical staining, Elisa and inverted-microscope. RESULTS: Transdifferentiation of cultured adult human retinal pigment epithelium cells to neurons was induced by blocking VEGF expression. The transdifferentiation was a direct phenotypic change from RPE cell to neurons without cell differentiation. The transdifferentiated neurons showed up-regulated expression of VEGF receptor 2 (Flk-1) and expressed several markers of retinal ganglion cell, including Thy1.1 and neurofilament. CONCLUSION: Blocking of VEGF expression and up-regulation of Flk-1 can induce transdifferetiation of adult human retinal pigment epithelium cells into ganglion cells.

Adult↗
PubMed2005

[Effects of hepatocyte growth factor on TGF-beta1 triggered tubular epithelial-myofibroblast transdifferentiation by CTGF in vitro].

OBJECTIVE: To observe the effects of hepatocyte growth factor (HGF) on TGF-beta1 triggered tubular epithelial-myofibroblast transdifferentiation (TEMT) and on the expression of connective tissue growth factor (CTGF). METHODS: The morphology of transdifferentiate tubular cells was observed using phase-contrast microscopy and scanning electron microscopy. alpha-SMA was assessed by immunohistochemistry and semiquantified by mean intergrated opitical density (IOD). The level of fibronectin (FN) in the culture supernatant was measured by ELISA. CTGF mRNA expression was examined by RT-PCR. RESULTS: The TGF-beta1-induced TEMT characterized by expression of alpha-SMA was shown by immunohistochemistry. TGF-beta1 was also shown to stimulate the secretion of FN in cultured supernatant and the CTGF mRNA expression of NRK52E cells. There was no statistically significant difference between HGF-treated groups and control group in the result of alpha-SMA immunostaining and the level of FN, except that CTGF mRNA expression was slightly increased in the HGF-treated groups. The addition of HGF inhibited the TGF-beta1-induced TEMT, the secretion of FN, and the CTGF expression of NRK52E cells, there was a significant correlation between the expression of CTGF and the expression of alpha-SMA. CONCLUSION: HGF could block TEMT and FN secretion triggered by TGF-beta1, which implies that HGF could participate in renal interstitial fibrosis as a negative regulator. The negative regulation of transdifferentiation of HGF may be partially achieved by attenuation of CTGF expression.

Animals↗
PubMed1989

[Gene expression during lens transdifferentiation from pigmented epithelial cells].

Pigmented epithelial cells of chicken and human dedifferentiate in the medium containing phenylthiourea and testicular hyaluronidase, and then trans-differentiate into lens cells in vitro. To understand the molecular mechanisms of transdifferentiation, gene expression during lens transdifferentiation was analyzed. As the first step, pigment cell and lens specific genes were isolated and expression of these gene was analyzed by Northern blotting . These results clearly shown that lens transdifferentiation proceeds via neutral cell state in which both pigment and lens specific genes are repressed. Oncogene expression was also analyzed. An elevated expression of the c-myc gene was observed during dedifferentiation process. It is expected that elevated expression of c-myc gene might prevent the cells from entering the G0 phase and thus lead to dedifferentiated state.

Animals↗
PubMed1988

Reversal of conjunctival transdifferentiation by topical retinoic acid.

After resurfacing a total corneal epithelial defect extending 2-3 mm beyond the limbus, conjunctival epithelium gradually loses goblet cells and transforms into a corneal-like epithelium. We examined the effect of topical retinoic acid on the reversal of transdifferentiation on nonvascularized corneas. Four months after total denudation of corneal epithelium using n-heptanol, rabbit corneas without vascularization received topical drops of 0.1% (wt/vol) all-trans retinoic acid in corn oil 3 times a day. Before treatment, the transdifferentiation was complete, as evidenced by the absence of goblet cells on the corneal surface using a topographical assay and routine histology. After treatment for 15 days, goblet cells reappeared 3 mm into the peripheral cornea, and extended in a centripetal density to 4.5 mm after 32 days. To prove that retinoic acid was not angiogenic, retinoid-bearing Elvax-40 pellets were implanted into normal corneal stroma. Taken together, these data indicate that vitamin A or retinoids may be an important factor in the modulation of conjunctival epithelial transdifferentiation.

Administration, Topical↗
PubMed1996

Transdifferentiated retinal pigment epithelial cells are immunoreactive for vascular endothelial growth factor in surgically excised age-related macular degeneration-related choroidal neovascular membranes.

PURPOSE: To determine the cellular origin and the vascular endothelial growth factor (VEGF) immunoreactivity of the nonvascular stromal cells in surgically excised age-related macular degeneration (ARMD)-associated choroidal neovascular membranes (CNVMs). METHODS: Immunohistochemical analysis was performed on frozen sections of eight surgically excised ARMD-related CNVMs. RESULTS: Cytokeratin-positive, smooth muscle actin-positive polygonal or fibroblastic (transdifferentiated RPE) cells were the principal nonvascular stromal cells detected. The polygonal cells were more commonly found in active (highly vascularized) regions and were strongly immunoreactive for VEGF. The fibroblastic cells were predominantly found in fibrotic (hypovascular) regions and were minimally immunoreactive for VEGF. CONCLUSIONS: Transdifferentiated RPE cells are the principal nonvascular stromal cells of both vascular and fibrotic ARMD-related CNVMs. Preferential localization of VEGF immunoreactivity with the cytoplasm of the polygonal transdifferentiated RPE cells in the highly vascularized regions of the surgically excised CNVMs suggests an important angiogenic role of these cells and this growth factor in the progression of ARMD-related choroidal neovascularization.

Actins↗
PubMed1996

Transdifferentiation of hepatic stellate cells (Ito cells) to myofibroblasts: a key event in hepatic fibrogenesis.

Hepatic stellate cells (HSC) are the major source of extracellular matrix components (ECM), if these precursor cells are activated in areas of necroinflammation to proliferate and to transdifferentiate from the retinoid storing to the ECM-producing phenotype termed myofibroblast (MFB). The mechanisms of HSC activation are crucial for the understanding of liver fibrogenesis. Activation is promoted by cytokines from Kupffer cells (KC) and platelets, of which TGF-beta is of great importance. It stimulates in HSC gene expression of ECM molecules but inhibits proliferation and induces phenotypic transdifferentiation. Latent TGF-beta is activated in cooperation with endothelial cells. TGF-alpha, also secreted by KC, stimulates HSC proliferation. In addition, hepatocytes (PC) enhance proliferation of HSC but ECM production is not affected. The mitogenic effect is mediated by TGF-alpha, IGF-1 and other cytokines. The paracrine signals of PC are increased by PC damage. During transdifferentiation MFB increasingly express TGF-beta and TGF-alpha, which are suspected to be involved in autocrine stimulation of MFB and paracrine activation of still untransformed HSC. A three-step cascade model of HSC activation is suggested. A preinflammatory phase initiates HSC activation by discharge of mitogenic cytokines (TGF-alpha, IGF-1) from damaged PC followed by the inflammatory phase based on cytokines (TGF-beta, etc.) from activated KC. In the postinflammatory phase MFB are stimulated by autocrine mechanisms contributing potentially to a perpetuation of the fibrogenic process even after cessation of the primary event (PC damage).

Animals↗