Secretory differentiation and cell type identification of a human fetal bronchial epithelial cell line (HFBE)

Immunohistochemical Detection of Carcinoembryonic Antigen (CEA) in non-neoplastic Lung Disease

Carcinoembryonic antigen (CEA), though typically associated with malignant epithelial neoplasms, is known to be present at elevated levels even in the serum of normal individuals and of patients suffering from interstitial diseases of the lung. Few reports have addressed the question of the possible source of CEA immunoreactivity within the lung parenchyma. Two patients with elevated CEA serum levels were studied by immunohistochemistry on open lung biopsy specimens. Two different antibodies (one absorbed with non-specific cross-reacting antigen, NCA) were used. The results show that bronchiolar cells and type II pneumocytes are focally positive with both antibodies; the immunoreaction is preserved even after absorption with NCA. In agreement with experimental data on CEA synthesis in fetal bronchial cell lines, these findings indicate that interstitial lung disorders may induce abnormal CEA-like substance expression. In these cases, where no epithelial neoplasms subsequently develop, the cutoff level for CEA in serum should be raised. Bronchiolar and alveolar cells appear primarily responsible for CEA-like substance production.

Novel approaches for studying pulmonary toxicity in vitro

The in vitro study of adverse cellular effects induced by inhaled pollutants poses a special problem due to the difficulties of exposing cultured cells of the respiratory tract directly to test atmospheres that can include complex gaseous and particulate mixtures. In general, there is no widely accepted in vitro exposure system. However, in vitro methods offer the unique possibility for use of human cells, developed and validated cell culture and exposure device (CULTEX(1)) using the principle of the air/liquid exposure technique. Cells of the respiratory tract are grown on porous membranes in transwell inserts. After removal of the medium, the cells can be treated on their superficial surfaces with the test atmosphere, and at the same time they are supplied with nutrients through the membrane below. In comparison with other experimental approaches, the goal of our studies is to analyze the biological effects of test atmospheres under environmental conditions, i.e. without humidifying the atmosphere or adding additional CO(2). The system used is small and flexible enough independent of a cultivation chamber and thus offers the opportunity for onsite study of indoor and outdoor atmospheres in the field. The efficacy of the exposure device has already been demonstrated in the analysis of dose-dependent cytotoxic and genotoxic effects of exposure of epithelial lung cells to complex mixtures such as native diesel exhaust and side-stream smoke.

A method for the in vitro exposure of human cells to environmental and complex gaseous mixtures: application to various types of atmosphere

The application of in vitro methods to the analysis of the effects of airborne materials is still limited, because there are no generally accepted concepts and technologies for efficiently exposing adherent growing cells to test atmospheres, especially those comprising complex mixtures of gaseous and particulate phases. The introduction of in vitro research into the field of inhalation toxicology offers a unique possibility for using human cells and tissues for pre-screening studies, thus reducing the necessity for animal experiments, and cutting the numbers of animals used in toxicological testing. We therefore developed a novel experimental concept that uses an exposure device based on the cell cultivation system CULTEX (Patent No. DE 198011763; PCT/EP99/00295). This allowed us to investigate environmental atmospheres, which were chemically and physically unmodified, in an in vitro system, by exposing the target cells directly at the air/liquid interface. The exposure device itself is small and flexible enough to be connected to a variety of aerosol-generating systems without the need for an incubator, as it fulfils all the requirements for maintaining cell viability over a defined period. The general applicability and the sensitivity of this in vitro approach for testing various generated atmospheres under the same cell-exposure conditions were demonstrated by studying dose-dependent cytotoxic effects in human lung epithelial cells exposed to air contaminated with single gases or complex mixtures, such as diesel exhaust fumes and side-stream cigarette smoke.

In vitro genotoxicity assay of sidestream smoke using a human bronchial epithelial cell line

Genotoxic effects of air contaminants, such as gaseous or particulate compounds, have been difficult to investigate due to inefficient methods for exposing cell cultures directly to these substances. New cultivation and exposure techniques enable treatment of epithelial cells with sample atmospheres with subsequent in vitro assays, as demonstrated by a new system called CULTEX (CULTEX: patent No. DE 19801763; PCT/EP99/00295), which uses a transwell membrane technique for direct exposure of complex mixtures, for example sidestream cigarette smoke, at the air/liquid interface. The sensitivity and susceptibility of human bronchial epithelial cells to this complex mixture have already been shown for cytotoxic endpoints. In this study, genotoxic effects of sidestream cigarette smoke at different concentrations were assessed using the alkaline comet assay. HFBE 21 cells were exposed for 1 h to clean air, nitrogen dioxide or sidestream smoke. Exposure of the cells to sidestream cigarette smoke induced DNA strand breaks in a dose-dependent manner. The combination of gas phase exposure and the comet assay provides a realistic and efficient model for sensitive detection of DNA strand breaks induced by airborne and inhalable compounds.

Exposure of human lung cells to native diesel motor exhaust--development of an optimized in vitro test strategy

To investigate the effects of native diesel motor exhaust on human lung cells in vitro, a new experimental concept was developed using an exposure device on the base of the cell cultivation system CULTEX (Patent No. DE19801763.PCT/EP99/00295) to handle the cells during a 1-h exposure period independent of an incubator and next to an engine test rig. The final experimental set-up allows the investigation of native (chemically and physically unmodified) diesel exhaust using short distances for the transportation of the gas to the target cells. The analysis of several atmospheric compounds as well as the particle concentration of the exhaust was performed by online monitoring in parallel. To validate the complete system we concentrated on the measurement of two distinct viability parameters after exposure to air and undiluted, diluted and filtered diesel motor exhaust generated under different engine operating conditions. Cell viability was not influenced by the exposure to clean air, whereas dose-dependent cytotoxicity was found contingent on the dosage of exhaust. Additionally, the quality of exhaust, represented by two engine operating conditions (idling, higher load), also showed well-distinguishable cytotoxicity. In summary, the experimental set-up allows research on biological effects of native engine emissions using short exposure times.

In vitro exposure of isolated cells to native gaseous compounds--development and validation of an optimized system for human lung cells

An exposure system for adherent growing cells to native gaseous compounds was developed using air/liquid culture techniques on the basis of the Cultex system'. In contrast to other exposure systems the reproducible testing of native environmentally relevant gases without changing their physical or chemical properties including heating, CO2- content and humidity is possible. Specially designed systems for medium flow and gas support guarantee the nutrification and humidification as well as the direct gas contact of the exposed cells which are cultivated on microporous membranes (0.4 microm pore size). The system works independently of a cell culture incubator offering the possibility to analyze any relevant gas mixture directly under indoor or outdoor conditions. Several experimental approaches were carried out to characterize the properties of the system. In exploratory experiments without cells, the reproducibility and quality of the gas/membrane contact could be demonstrated. Exposures of human lung fibroblasts (Lk004 cells) and human lung epithelial cells (HFBE-21 cells) to synthetic air, ozone (202 ppb, 510 ppb) and nitrogen dioxide (75 ppb to 1,200 ppb) established that cells could be treated for 120 minutes without significant loss of cellular viability. At the same time, the experiments confirmed that such exposure times are long enough to detect biological effects of environmentally relevant gas mixtures. The analysis of viability (viable cell number, tetrazoliumsalt cleavage) and intracellular end-points (oxidized/reduced glutathione, ATP/ADP) showed that both gases induced relevant cellular changes. In summary, the efficiency and practicability of this newly developed exposure system for adherent human lung cells could be clearly demonstrated.

A method for in vitro analysis of the biological activity of complex mixtures such as sidestream cigarette smoke

Studies of the cytotoxicity of air contaminants such as gaseous or particulate compounds and complex mixtures have traditionally used in animal experiments because of the difficulties in exposing cell cultures directly to these substances. New cultivation and exposure techniques enhance the efficiency of in vitro methods, as demonstrated by a new system called CULTEX* which uses a transwell membrane technique for direct exposure of complex mixtures like sidestream cigarette smoke at the air/liquid interface. The factors influencing the susceptibility of human bronchial epithelial cells (e.g. gas flow rate or duration of exposure) were studied and the cells were finally exposed for one hour to clean air or different concentrations of sidestream smoke. The biological parameters estimated were number of cells, metabolic activity and glutathione concentration. After exposure of the cells to sidestream cigarette smoke, dose-dependent effects were measured. Thus, the introduction of these cultivation and exposure techniques offers new testing strategies for the toxicological evaluation of a broad range of airborne and inhalable compounds.

CULTEX--an alternative technique for cultivation and exposure of cells of the respiratory tract to airborne pollutants at the air/liquid interface

The assessment of cytotoxicity of air contaminants such as gaseous or particulate compounds and complex mixtures has traditionally involved animal experiments, due to the difficulties in exposing cell cultures directly to these substances. New cultivation and exposure techniques enhance the efficiency of in vitro studies, as demonstrated by a new experimental system called CULTEX which allows direct exposure of cells at the air/liquid interface. In this case, human bronchial epithelial cells are cultivated on porous transwell membranes in a device allowing intermittent medium supply. The medium is pumped into a special modular culture unit through the transwell membrane supporting the cells. At certain time intervals, the medium is completely removed and the cells can be maintained and exposed at the air/liquid interface until the next medium supply without loss of viability. In comparison to conventional submersed culture conditions, the cells have been grown on transwell membranes using the new pulse submersion technique. There are no deleterious effects on cell viability due to the direct exposure to airborne pollutants. Thus, the introduction of these new cultivation and exposure techniques offers new testing strategies for the toxicological evaluation of inhalable soluble and inert substances as well as complex mixtures.

Stem cells of the respiratory epithelium and their in vitro cultivation

Parenchymal (epithelial or mesenchyma) stem cells are rapidly drawing both scientific and clinical attention in solid organs like the liver, skin, intestine and abdominal mesothelium, just as has been the case in the hematopoietic system. For the stem cells of these organs various definitions, markers for identification, methods of isolation and in vitro cultivation, and lineage mechanisms have been proposed and some of them are now proven to be valid and useful. In this article attempts will be made to explore whether there are stem cells in the lower respiratory system (from the trachea to the lung periphery) and what they look like. Because of its anatomical and functional complexity the stem cell concept for the respiratory system has been developing rather slowly. Nevertheless, the data available seem to indicate that in analogy to the above mentioned organs there is only one type of epithelial stem cells throughout all sections of the lower respiratory system during fetal through adult stages. They are multipotent for cell differentiation and able to yield lineage progenitors for ciliated, goblet, basal. Clara neuroendocrine, alveolar type 1 and alveolar type 2 cells.

Effects of vitamin A on proliferation of human distal airway epithelial cells in culture

Using a serum-free culture method, we investigated the effects of vitamin A on the proliferation of human distal airway epithelial cells. Outgrowth of epithelial cells from lung tissue explants was enhanced by treatment with all-trans retinol at concentrations of 10(-8) to 10(-7) M. The colony-forming activity of cells harvested from the primary culture and replated onto Swiss 3T3 fibroblastic feeders was, in contrast, significantly reduced by 10(-7) M to 10(-5) M retinol. When the primary cells were harvested and subcultured on Primaria plates, population expansion was also inhibited by retinol at 10(-10) to 10(-6) M. We further investigated the cells to determine whether there was any difference in sensitivity to the growth-inhibitory effects of vitamin A between cells from the primary culture incubated with and without retinol. The population increase in cells harvested from the primary culture was inhibited equally in retinol-treated and non-treated cells by subsequent treatment with retinol or retinoic acid, this inhibition being dose-dependent. DNA synthetic activity was also inhibited. Interestingly, both the growth rate and the colony-forming efficiency on feeders were greater in the subculture of cells from the retinol-treated primary culture than in those non-treated. When the cells in the secondary subculture were treated with retinoic acid and replated again, they showed a greater population increase rate than those non-treated. Our results showed that human distal airway epithelial cells isolated from lung tissue were sensitive to the growth-inhibitory effect of vitamin A, but the proliferative potential in some fraction of the epithelial cell population was possibly enhanced by vitamin A treatment.