Biomedical subjects

W I De Boer

Publications and source records attributed to W I De Boer.

6 recordsLinked to original sources

PubMed2002

Cytokines and therapy in COPD: a promising combination?

COPD is a major health problem, with patients showing a progressively declining, largely irreversible, change in lung function. This is associated with chronic airways inflammation and structural remodeling, including loss of alveolar walls, and goblet cell metaplasia with mucus hypersecretion. Inflammatory cells may contribute to the airway remodeling via secretion of proteases, fibrotic or mitogenic growth factors, and cytokines. In turn, airway remodeling may contribute to the clinical symptoms of COPD. Currently available therapies are directed to improvement of clinical symptoms and reduction of the airways inflammation. The commonly used glucocorticosteroids are expected to reduce the inflammation by acting on kinases or transcription factors necessary for expression of pro-inflammatory cytokines or chemokines. However, several long-term and short-term studies showed that glucocorticosteroids are rather ineffective in improving lung function and reducing the airway inflammation in patients with COPD. New therapeutic strategies may reduce the inflammation and alleviate the clinical symptoms of COPD. Tumor necrosis factor-alpha, interleukin-8, and monocyte chemoattractant protein-1 are important chemotactic proteins for macrophages and neutrophils, the predominant inflammatory cells associated with COPD. As lung levels of these cytokines are higher in COPD compared to non-COPD patients, they may represent targets for novel therapies.

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PubMed2001

Image analysis and quantification in lung tissue.

On 9-10 September 1999, an international workshop on image analysis and quantification in lung tissue was held at the Leiden University Medical Center, Leiden, The Netherlands. Participants with expertise in pulmonary and/or pathology research discussed the validity and applicability of techniques used for quantitative examination of inflammatory cell patterns and gene expression in bronchial or parenchymal tissue in studies focusing on asthma and chronic obstructive pulmonary disease (COPD). Differences in techniques for tissue sampling and processing, immunohistochemistry, cell counting and densitometry are hampering the comparison of data between various laboratories. The main goals of the workshop were to make an inventory of the techniques that are currently available for each of these aspects, and in particular to address the validity and unresolved problems of using digital image analysis (DIA) as opposed to manual scoring methods for cell counting and assessment of gene and protein expression. Obviously, tissue sampling and handling, fixation and (immunohistochemical) staining, and microscope settings, are having a large impact on any quantitative analysis. In addition, careful choices will have to be made of the commercially available optical and recording systems as well as the application software in order to optimize quantitative DIA. Finally, it appears to be of equal importance to reach consensus on which histological areas are to be analysed. The current proceedings highlight recent advances and state of the art knowledge on digital image analysis for lung tissue, and summarize the established issues and remaining questions raised during the course of the workshop.

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PubMed1997

Expression and functions of EGF, FGF and TGFbeta-growth-factor family members and their receptors in invasive human transitional-cell-carcinoma cells.

Studies on epidermal-growth-factor-like-, fibroblast- and transforming growth factors suggested their implication in tumorigenesis involving effects on tumour-cell proliferation and migration. In human transitional-cell carcinomas (TCC), enhanced expression of TGF alpha and EGF receptors correlated with an aggressive phenotype. However, little is known about functions of these growth factors in invasive TCCs. In this study, we performed protein- and RNA-expression studies on a set of growth factors and their receptors on the newly established invasive human TCC cell line designated 1207. The data were correlated with functional proliferation and migration studies. Similar expression patterns of many cellular markers, growth factors and their receptors were noted both in the original TCC tissue and in its derivative cell line, indicating the relevance of this cell line to the investigation of growth factor functions on TCC cells. The proliferation induction by EGF, TGF alpha, amphiregulin, heregulin alpha, FGF-1 and FGF-7 correlated with the presence of EGF receptors, c-erbB4 and FGFR2 (IIIb), respectively. Amphiregulin and heregulin alpha induced the most proliferation. In conformity with the low expression of TGF beta receptors I and II, TGF beta1, barely inhibited proliferation, while TGF alpha induced invasion of 1207 cells into Matrigel. These data support the notion that notably EGF-like proteins mediate TCC growth and invasion through autocrine pathways which can be reinforced by loss of TGF beta1 regulation.

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PubMed1994

An in vitro model of urothelial regeneration: effects of growth factors and extracellular matrix proteins.

Although the cellular turnover of resting urothelium is very low, its regenerative capacity is known to be outstanding. In organotypic mouse urothelial cultures closely mimicking the differentiation and multilayering of normal urothelium, we examined the cell biological mechanisms underlying urothelial regeneration and the specific role of growth factors and several extracellular matrix (ECM) components. Exposure to epidermal growth factor (EGF) and acidic fibroblast growth factor (aFGF) and culture on laminin resulted in enhanced expansion of the urothelium. Microscopy and assessment of proliferative activity revealed that enhanced urothelial expansion due to EGF could be attributed to increased proliferative activity and an increase in cell numbers, whereas aFGF-stimulated expansion must be considered the consequence of increased cellularity and migration. Laminin-enhanced urothelial expansion was shown to be the result of spreading of the entire urothelial organotypic culture. This was associated with a considerable decrease in the number of cell layers. A synergistic effect of growth factors and laminin was not found. This organotypic urothelial cell culture model seems to be very useful in studying strategies to improve urothelial regeneration.

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PubMed1994

Multiparameter analysis of primary epithelial cultures grown on cyclopore membranes.

The use of porous membranes as culture support for epithelial cells has previously been shown to cause functional differentiation of these cells mimicking an in vivo condition, in contrast to culture on plastic. The different materials of which the membranes are made also have different properties, such as transparency, rigidity, and retention of molecules. Cyclopore membranes (polyethylene terephtalate) are permeable, transparent, rigid, and have low protein retention. In this study we examined the applicability of assessing multiple parameters on a single culture of primary epithelial cells on a Cyclopore membrane. Cultures of transitional epithelial cells on these membranes differentiate into an organoid-like epithelium. We were able to perform morphometric analysis during and after cell culture and to quantitate proliferation and differentiation by double immunoenzymatic staining. On these cultures, quantitative radiochemical analysis could also be achieved, retaining the morphology and the immunohistochemical staining. Cross-sections of paraffin-embedded and plastic-embedded cultures were analyzed qualitatively by light and transmission electron microscopy, respectively. Finally, cytokeratins in these cultures could also be visualized by immunofluorescence analysis. This suitability for simultaneous assessment of both qualitative and quantitative parameters on a single cell culture grown on a Cyclopore membrane reduces the need of biological materials and may lead to better insight into physiological processes.

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PubMed1993

Characterization of mouse urothelial cell lines in different phases of transitional-cell carcinogenesis.

Altered cellular responsiveness to growth factors is one of the factors involved in carcinogenesis. In order to study the role of growth factors in transitional-cell carcinogenesis, we established 3 urothelial cell lines from normal mouse urothelium, designated g/G, NUC-5 and NUC-I. These cell lines were studied by light and transmission electron microscopy, karyotyping, grafting in syngeneic mice, growth-factor response in vitro under serum-free conditions, and EGF receptor expression. In the presence of insulin or insulin-like growth factors I and II, proliferation of the non-tumorigenic DNA-tetraploid g/G and DNA aneuploid NUC-5 cells is stimulated by EGF, TGF alpha, bFGF and aFGF. This stimulation can be abolished in g/G but not in NUC-5 cells by simultaneous addition of TGF beta. Proliferation of g/G and NUC-5 cells can also be stimulated by PDGF-AA. The spindle-cell-like NUC-I cells are DNA aneuploid and tumorigenic in syngeneic mice; they express low levels of EGF receptors and their autonomous proliferation is only affected by insulin or insulin-like growth factors. Each of these cell lines seems to reflect a different phase in transitional-cell carcinogenesis: g/G cells have gained immortality, have become tetraploid, but are non-tumorigenic and growth-factor-dependent. NUC-5 cells have become aneuploid, have a growth-factor responsiveness different from that of normal epithelial cells, but are still non-tumorigenic. NUC-I cells are aneuploid, tumorigenic, and growth-factor-independent. These urothelial cell lines provide a suitable tool for further studies in transitional-cell carcinogenesis.

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