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R De Vos

Publications and source records attributed to R De Vos.

At least 37 records · Page 2Linked to original sources
PubMed1999

Multi-layered periodontal pocket epithelium reconstituted in vitro: histology and cytokeratin profiles.

BACKGROUND: In order to study inter-individual differences in bacterial adhesion/invasion of periodontal tissues, an in vitro model for culturing multi-layered pocket epithelium without feeder layers or stromal equivalents (including the evaluation of their cytokeratin profiles) was developed. METHODS: Pocket epithelium was collected and grown until confluent in Falcon flasks using keratinocyte-serum free medium (KSFM), without a feeder layer. In the second passage, oral keratinocytes were re-grown in a 2 compartment system using either a clear polyester (transwell-clear [TCL]) or a collagen (transwell-col [TCO]) membrane as culture surface. After the first week, the calcium concentration was raised to 1.2 mM and in half the wells, the KSFM was supplemented with 10% fetal calf serum (FCS). Histology and immunohistochemistry were performed after 1, 2, and 3 weeks of additional growth. RESULTS: In general, all conditions resulted in a structured epithelium consisting of 3 to 5 layers, but important differences were observed between the membrane types and between the media. CK4 was rarely and only lightly expressed while CK18 and 19 (characteristic of junctional epithelium) were very strongly expressed in the older (2 and 3 weeks) cultures. CK13 and 14 (characteristic of any stratifiable epithelial cell) also tended to increase over time; CK13 seemed to be stronger in KSFM with FCS while the contrary was true for CK14. The multi-layer created by the combination TCL/KSFM + 10% FCS resembled a junctional epithelium most, while that grown on TCO without FCS mimicked the sulcular epithelium. CONCLUSIONS: It seems possible to create a histiotypic culture resembling either periodontal pocket or junctional epithelium without the use of stromal equivalents or feeder layers which make this approach more cumbersome. This multi-layered culture offers a model to investigate the permeability of pocket epithelium and the adhesion and penetration of bacteria under well-defined environmental conditions.

Animals↗
PubMed1998

Primary rat lacrimal cells undergo acinar-like morphogenesis on reconstituted basement membrane and express secretory component under androgen stimulation.

Single cells or small cell clusters, isolated from the rat lacrimal gland, were incubated on reconstituted basement membrane (matrigel) in a well-defined serum-free medium. During the first days of culture, cells reassociated and reorganized in structures resembling acini. These multicellular structures, maintained in culture for 2 weeks, consisted of well-polarized cuboidal cells surrounding a central lumen and exhibiting apically located microvilli. Myoepithelial cells were observed at the periphery of the acinar structures. Both in the native lacrimal and in the cultured aggregates, epithelial cells displayed strong immunoreactivity for cytokeratin 8, while myoepithelial cells were immunoreactive for vimentin and alpha-smooth muscle isoactin. These data indicate that the cultured aggregates closely mimic the in vivo architecture of lacrimal glands both by morphology and immunohistochemistry. We further demonstrated the presence of an intact androgen receptor and the ability of the cultured aggregates to respond to androgens with increased secretion of the secretory component. Comparable androgen responses were observed in lacrimal gland cultures of 5-week-old male and female rats. In conclusion, we report a morphologically and functionally differentiated culture system of primary rat lacrimal cells, in which androgen-regulated gene expression was observed. This culture model provides a unique experimental paradigm for studying the effects of hormones, cytokines, and growth factors on the morphogenesis, growth, and functional differentiation of lacrimal glands.

Actins↗
PubMed1998

Heparan sulphate proteoglycan expression in human primary liver tumours.

Heparan sulphate proteoglycans (HSPGs) play important biological roles in cell-matrix adhesion processes and are essential regulators of growth factor actions (e.g., as co-receptor for hepatocyte growth factor). Since in liver carcinogenesis, interactions between cells, the matrix, and growth factors play a major role, the aim of this study was to investigate whether the distribution pattern of HSPGs is altered in human primary liver tumours. Twenty-two primary liver tumours and five normal liver biopsies were studied, using specific monoclonal antibodies against syndecans-1, -2, -3, and -4; glypican; perlecan; and heparan sulphate chains. Cholangiocarcinomas as well as hepatocellular carcinomas showed an altered immunoreactivity pattern of the different HSPGs in comparison with normal liver parenchyma, probably reflecting the growth regulatory roles of HSPGs. Intracellular positivity for integral membrane HSPGs syndecan-1 and especially syndecan-4 was a constant finding in most tumours, suggesting increased synthesis or internalization of these HSPGs. Syndecan-3 and perlecan expression in tumours was found in an expected distribution pattern. The strong reactivity for syndecan-3 and perlecan in tumoral stromal vessels might suggest a role for these HSPGs in tumoral angiogenesis. In addition, perlecan probably exerts its known growth factor reservoir function also in the stroma of primary liver tumours.

Bile Duct Neoplasms↗
PubMed1998

Hepatic OV-6 expression in human liver disease and rat experiments: evidence for hepatic progenitor cells in man.

BACKGROUND/AIMS/METHODS: Since in rat experiments, activation of progenitor cells is seen in conditions associated with hepatocyte injury or inhibited replication, we compared the activation and fate of human putative progenitor cells in regenerating liver versus chronic cholestatic disease, using immunohistochemistry, rat oval cell marker OV6 and a panel of bile ductular cell markers. We compared the results with different rat models: the choline-deficient acetylaminofluorene (CDAAF)- and alpha-naphthylisothiocyanate (ANIT)-model, using immunohistochemistry and electron microscopy. RESULTS: In very early stages of human liver regeneration, putative progenitor cells in the vicinity of portal tracts were immunoreactive for OV6, CK7, CK19 and chrom-A. In later stages of regeneration and in chronic cholestasis, reactive bile ductules (immunoreactive for OV6, CK7, CK19, chrom-A, NCAM) and intermediate hepatocyte-like cells (immunoreactive for OV6, CK7, chrom-A), became apparent, suggesting bidirectional differentiation of the putative progenitor cells. In regenerating human liver, intermediate hepatocyte-like cells became more numerous with time and extended far into the lobule. In advanced cholestasis, intermediate hepatocyte-like cells were less numerous and formed periportal rosettes and small clusters. In the CDAAF rat model (associated with inhibited hepatocyte replication), but not in the ANIT model, gradual differentiation of oval cells into hepatocytes was seen after stopping the diet. CONCLUSIONS: Our results in human liver suggest that reactive ductules and intermediate hepatocyte-like cells originate at least partly from activation and differentiation of "progenitor cells". In regeneration after submassive necrosis, in analogy with what is seen in rat models, differentiation towards hepatocytes is more pronounced than in chronic cholestasis.

Animals↗
PubMed1998

Primary liver tumour of intermediate (hepatocyte-bile duct cell) phenotype: a progenitor cell tumour?

A 57-year-old female patient presented with painless obstructive jaundice and mild mesogastric pain; she was in good general condition on admission. Abdominal ultrasonography revealed diffuse tumoral invasion of the liver, suggesting diffuse metastases. A liver biopsy showed a tumour with a trabecular growth pattern, composed of uniform relatively small cells, very suggestive of an endocrine carcinoma. Additional immunohistochemical stains, however, did not show any endocrine differentiation, but showed positivity for both hepatocyte-type cytokeratins (cytokeratin 8 and 18) and bile duct-type cytokeratins (cytokeratin 7 and 19). In addition, parathyroid hormone-related peptide, shown to be a good marker for cholangiocarcinoma, was immunoreactive. Electron microscopy revealed tumour cells with an intermediate phenotype: the cells clearly showed hepatocyte features on one hand and bile duct cell features on the other hand. Nine days after admission, the patient died due to liver failure and hepatic encephalopathy. Autopsy excluded another primary tumour site. Overall, this tumour was a primary liver tumour with an intermediate phenotype and with a very rapid clinical course. The intermediate (between hepatocyte and bile duct cell) phenotype suggests an immature progenitor cell origin, which is concordant with a rapid clinical course. This type of tumour has not been described previously and provides additional evidence for the existence of progenitor cells in human liver.

Bile Ducts↗
PubMed1998

Human CTLA-4 is expressed in situ on T lymphocytes in germinal centers, in cutaneous graft-versus-host disease, and in Hodgkin's disease.

Cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4, CD152) is a molecule expressed on in vitro activated T cells. CTLA-4 shares important sequence homology with CD28 and binds to the same ligands, CD80 (B7-1) and CD86 (B7-2). CTLA-4 probably functions as a negative regulator of T lymphocyte activation in the mouse, although this remains to be proven for human T lymphocytes. We have developed new monoclonal antibodies against human CTLA-4 and have investigated the in situ expression of CTLA-4 in a wide variety of normal and pathological human tissues expressing CD80 and CD86. As revealed in this study, CTLA-4 is expressed on thymocytes in thymic medulla, on a subset of CD4+ T lymphocytes in germinal centers of follicular hyperplasia, on T cells, mainly CD8+, infiltrating skin affected by graft-versus-host disease, and on T cells, mainly CD4+, infiltrating Hodgkin's disease lesions. In immunoelectron microscopy, CTLA-4 was found on the plasma membrane as well as in the hyaloplasm and cytoplasmic vesicles, in agreement with its pattern of expression on in vitro activated T cells. Interestingly, no or at most scarce expression of CTLA-4 was found in granulomatous lymph nodes, T-cell-mediated inflammatory diseases, or non-Hodgkin's lymphomas, regardless of their expression of CD80 or CD86. Thus, expression of CTLA-4 appears to be induced in selective pathological conditions in vivo. The pathways leading to selective induction of CTLA-4 and its role in the pathophysiology of these conditions need to be further investigated.

Abatacept↗
PubMed1997

Elevation of the serum bilirubin diconjugate fraction provides an early marker for cholestasis in the rat.

AIMS/METHODS: During cholestasis, components normally excreted into bile, e.g. bilirubin, accumulate in liver cells and biliary passages. In order to assess the conjugation of bilirubin retained in the hepatocyte during cholestasis, we analyzed the pattern of bilirubin pigments in rat serum and bile, using reversed phase alkaline methanolysis-HPLC. Cholestasis was induced by bile flow interruption for 1 to 2 h. RESULTS: One hour after initiation of cholestasis, the serum concentration of total bilirubin rose 2-fold due to increases in bilirubin di- (BDC) and monoconjugate (BMC), while unconjugated bilirubin (UCB) decreased by 33%. As a result, the BDC/BMC ratio increased to 1.67+/-0.20 vs 0.60+/-0.10 in controls (p<0.01) and the BMC/UCB ratio to 1.0+/-0.2 vs 0.1+/-0.1 (p<0.01). After relief of biliary obstruction, biliary output rose to 8.0+/-0.5 vs 5.5+/-0.3 micromol x min(-1) x kg (p<0.01), and the biliary BDC/BMC ratio to 4.0+/-0.3 vs 1.5+/-0.2 (p<0.01). In contrast, the biliary BMC/UCB ratio remained unchanged throughout. Increasing the duration of obstruction to 2 h led to a further increase in the serum BMC/UCB ratio to 2.2+/-0.3 (p<0.01), but not in the BDC/BMC ratio. Serum aminotransferase activity and the concentration of total bile acids increased 3- and 100-fold above their respective control values. Alkaline phosphatase activity remained unaltered, and electron microscopical features of cholestasis became apparent only after 2 h of biliary obstruction. CONCLUSIONS: We suggest that one of the initial events of cholestasis is a more efficient conjugation of bilirubin retained in the hepatocyte. This results in a shift of the equilibrium among bilirubin pigments towards BDC, the end-product of conjugation. Such a shift provides an early marker for cholestasis.

Alkaline Phosphatase↗
PubMed1997

Neuromuscular choristoma (hamartoma) with smooth and striated muscle component: case report with immunohistochemical and ultrastructural analysis.

Benign peripheral nerve tumors with a mesenchymal component are rare and are represented principally by the neuromuscular choristoma. We describe an 11-month-old male infant who presented with a mass arising from the left brachial plexus. The lesion was bound firmly to the involved nerves and consisted histologically and ultrastructurally of bundles of well-differentiated smooth muscle cells intermingled with striated muscle fibers and unmyelinated nerve fibers. In the 13 previously published cases of neuromuscular choristoma, no smooth muscle component was observed. This unique peripheral nerve choristoma with not only striated but also smooth muscle closely resembled neuromuscular choristoma and was considered a variant of it.

Brachial Plexus↗
PubMed1997

Primary osteorhabdomyosarcoma (malignant mesenchymoma) of bone: a case report and review of the literature.

Primary malignant mesenchymoma of bone is a rare neoplasm consisting of two or more unrelated malignant mesenchymal components other than fibrosarcoma or malignant fibrous histiocytoma. The literature reports fewer than 15 cases, most of which were composed of osteosarcoma and liposarcoma. We report an exceedingly rare case of primary malignant mesenchymoma of bone composed of osteosarcoma and rhabdomyosarcoma (osteorhabdomyosarcoma), arising in the right proximal tibia of a 21-year-old woman. We review the literature and compare primary malignant mesenchymoma of bone with dedifferentiated chondrosarcoma and conventional intramedullary osteosarcoma.

Adult↗
PubMed1996

Ichthyosis-characteristic appearance-mental retardation syndrome with distinct histological skin abnormalities.

In this report, we describe a 2.5-year-old severely mentally retarded boy with peculiar appearance and generalized ichthyosis, born to consanguineous Turkish parents. The histological finding in the skin biopsy of unusually large oval keratohyalin granules in the granular cells is unique, and hitherto has not been reported in other ichthyosis-mental retardation syndromes.

Abnormalities, Multiple↗
PubMed1996

The t(1;12)(p36;q13) in a renal oncocytoma.

A new chromosome rearrangement, t(1;12)(p36;q13), is added to the cytogenetic changes found in renal oncocytomas. The breakpoint in 12q is cytogenetically different from those of the MAR region, and molecularly HMGIC located in 12q15 on the basis of 3' RACE experiments does not seem to be directly involved.

Adenoma, Oxyphilic↗
PubMed1996

Small, freshly arrived histiocytes in cutaneous and mucosal herpetic lesions.

We report on the predominance of a special type of small histiocyte in the inflammatory infiltrate accompanying herpetic bullae. These histiocytes, which have previously been taken to be neutrophils, are freshly arrived cells with a hitherto unknown function. Until now, they have been found only in Sweet's syndrome and erythema nodosum where they form Miesscher's radial granulomas. Similar small histiocytes were found in half of those herpetic lesions with intact bullae, and in over two-thirds of ulcerated lesions in which these cells formed a palisade in the fibrinoid material covering the floor of the ulcerated vesicles. Small histiocytes, admixed with neutrophils, were in close proximity to virally infected keratinocytes. Immunohistochemical analysis confirmed their histiocytic nature. With the exception of ecthyma contagiosum (orf), similar small histiocytes were not found in other viral infections or in nonspecific ulcers of the skin. In cases of herpetic folliculitis, small histiocytes showed massive epidermotropism towards hair follicle epithelium. We conclude that cutaneous and oral herpetic infections represent yet another disease in which small, freshly arrived histiocytes occur. They may be involved in antigen presentation, or in killing of infected keratinocytes.

Antigens, CD↗
PubMed1996

'Undifferentiated progenitor cells' in focal nodular hyperplasia of the liver.

Focal nodular hyperplasia is a tumour like lesion, characterized by a central fibrous scar with irradiating fibrous septa that surround hyperplastic nodules and contain multiple bile ductules. The origin of the bile ductular structures is not clear. Recently, we found evidence for the existence of human counterparts of rat oval cells (potential stem cells) that have the ability of differentiating towards both bile duct cells and hepatocytes. These cells were found in regenerating human liver as well as in chronic cholestatic conditions. Because cholestatic features are seen in focal nodular hyperplasia, we initiated an immunohistochemical study on 23 surgical specimens using antibodies specific for cytokeratins 7 and 19 (bile duct type cytokeratins), OV6 (rat oval cell marker), chromogranin-A (shown to be positive in reactive bile ductules and human oval-like cells) and neural cell adhesion molecule--NCAM (shown to be positive in reactive bile ductules) to investigate whether 'undifferentiated progenitor cells' are also present in focal nodular hyperplasia. Electronmicroscopy was applied in five cases. Bile ductules invariably showed immunoreactivity for CK7 and 19, OV6, chromogranin-A and NCAM. In addition, small individual cells with an oval nucleus and a small rim of cytoplasm, in the vicinity of the septa, were immunoreactive for chromogranin-A, CK7 and 19 and OV6. These cells were hardly recognizable on routine light microscopy. Clusters of periseptal hepatocytes, seemingly in continuity with bile ductular structures, had a transitional phenotype: they stained positive for chromogranin-A, CK7 and OV6 and sometimes formed liver cell rosettes. The number of OV6-positive hepatocytes was greater than the number of chromogranin-A and CK7 positive hepatocytes. This indicates that, in human liver, OV-6 is not purely a marker of progenitor cells. Ultrastructurally, small immature cells, highly resembling rat oval cells, were recognized in the vicinity of septa. In addition, transitional cells displaying characteristics both of hepatocytes and bile duct cells were also present. These results confirm the presence of 'undifferentiated progenitor cells' in focal nodular hyperplasia and suggest that the ductular reaction in these lesions results, at least partly, from activation of these cells.

Animals↗
PubMed1996

Heparan sulfate proteoglycan expression in chronic cholestatic human liver diseases.

The mechanism of bile ductular reaction and accompanying fibrogenesis depends on interactions of ductular cells with the matrix and growth factors. Heparan sulfate proteoglycans (HSPGs) are essential cofactors in cell-matrix adhesion processes, in cell-cell recognition systems, and in receptor-growth factor interactions. We used monoclonal antibodies specific for the cell surface HSPGs (syndecans, glypican), for matrix HSPG (perlecan), and for heparan sulfate carbohydrate (HS) to investigate their immunohistochemical expression in 20 specimens with chronic cholestatic liver disease and in five normal human liver specimens. Because activated hepatic stellate cells (HSC are a major source of fibrosis in the liver, we also examined HSPG expression in primary cultures of human activated HSC using immunocytochemistry and Western blotting and for syndecan-1 also Northern blotting. In comparison with bile ductular cells of normal liver, reactive ductules in chronic cholestasis were marked by an elevated expression of syndecan-1, surrounded by an increased perlecan expression. In acinar zone 1, large stimulated macrophages and HSC, present in increased numbers, were strongly positive for syndecan-3. Cultured HSC showed a membranous staining pattern for syndecan-1, syndecan-3, and heparan sulfate, and in addition intracellular staining for syndecan-2, -3, and 4. Perlecan immunoreactivity was detected as intercellular strings. Western blotting revealed positive bands with all antibodies and Northern blotting for syndecan-1 was also positive. These results show that cultured human HSC can synthesize all four syndecans, glypican, and perlecan. These data reveal changes in the expression of syndecan-1, syndecan-3, and perlecan in human chronic cholestatic liver disease, that may be important in the deposition of matrix components and activation of growth factors that support ductular reaction and accompanying fibrogenesis.

Antibodies, Monoclonal↗
PubMed1995

Direct podocyte damage in the single nephron leads to albuminuria in vivo.

The hypothesis that detachment of podocytes leads to albuminuria was tested by studying the single nephron albuminuria in vivo after injecting a saponin solution (0.6 mg/ml) in Bowman's space of superficial glomeruli, which produces selective damage of the podocytes, in female Munich-Wistar-Frömter rats. Animals were subsequently installed under a fluorescence microscope, a purified fluoresceinated rat albumin solution was intravenously injected and the passage of the fluorescent albumin was followed through the microscope. Of the 47 glomeruli injected with the saponin solution (in 6 animals) 46 became fluorescent within seconds with the fluorescence progressing from Bowman's space into the proximal tubule and then in the rest of the tubule. In superficial non-injected and control-injected glomeruli weak fluorescence could be detected only in the glomerular tuft and the peritubular capillaries. Tubuli injected with the saponin solution remained indistinguishable from non-injected tubuli. Electron microscopic study of the saponin-injected glomeruli confirmed the selective removal of podocytes. Immunogold electron microscopy confirmed that the intact albumin molecule effectively passed the glomerular capillary wall at the site where podocyte detachment had occurred. It is concluded that selective removal of podocytes at the single nephron level leads to albuminuria in vivo, and therefore podocytes play a crucial role in regulating the permeability of the glomerular capillary wall.

Albumins↗
PubMed1995

Monosomy 22 in a malignant peripheral nerve sheath tumour of the kidney in childhood: a genetic link with other malignant paediatric renal neoplasms?

A recurrent malignant spindle cell neoplasm of the kidney, occurring in a 11-year-old girl and corresponding to a malignant peripheral nerve sheath tumour is reported. The neurogenic differentiation was substantiated by the presence of PGP 9.5 neurofilament and S-100 protein positivity and by the ultrastructural features. Cytogenetic analysis revealed monosomy of chromosome 22 in the tumour while the constitutional karyotype was normal. Primary malignant peripheral nerve sheath tumour of the kidney is extremely rare and should, on morphology, be differentiated from stromal predominant Wilms' tumour and clear cell sarcoma of kidney. Involvement of chromosome 22 has been described in a number of malignant renal tumours of childhood, such as Wilms' tumour (deletion), clear cell sarcoma (translocation), and rhabdoid tumour (deletion and translocation), thus suggesting common molecular mechanisms in pediatric malignant renal tumours.

Child↗
PubMed1995

Heparan sulfate proteoglycan expression in normal human liver.

Because increasing evidence implicates heparan sulfate proteoglycans (HSPGs) as essential cofactors in receptor-growth factor interactions, in cell-cell recognition systems, and in cell-matrix adhesion processes and yet little is known about their cellular distribution pattern and cellular sources in liver tissue, we used monoclonal antibodies specific for the core proteins of syndecan1, 2, 3, 4, glypican, and perlecan to investigate their immunohistochemical expression in normal adult human liver biopsy specimens. Syndecan1 was expressed in sinusoidal endothelial cells, whereas the endothelium of the portal tract vessels was negative. Hepatocytes showed a membranous staining pattern of the sinusoidal and intercellular domain. Bile duct epithelial cells showed basolateral membrane positivity. Immunoreactivity for syndecan2 was seen in mesenchymal cells, accentuated around bile ducts. Syndecan3 showed intense staining of hepatic arterial and portal venous endothelial cells, of mesenchymal cells, and of Ito cells. Immunohistochemistry for syndecan4 showed a granular staining pattern of hepatocytes at their bile canalicular pole. Glypican showed weak positivity in portal tract mesenchymal cells and clear positivity in nerve bundles. Perlecan was present in Disse's space, in endothelial cells, in basement membranes surrounding bile ducts and vessels, in vessel walls, and in mesenchymal cells. The highly differential expression of these HSPGs in the different cell compartments of the liver, as well as in basement membranes and in Disse's space, suggests that each of these proteoglycans has a specific function in the interplay of cells, matrix molecules, growth factors, and proteinases.

Cells, Cultured↗