Stable ciliary activity in human nasal epithelial cells grown in a perfusion system

Skin irritation and inhalation toxicity of biocides evaluated with reconstructed human epidermis and airway models

Biocides are widely used in household products. Humans are exposed to biocides through dermal, inhalational, and oral routes. However, information on the dermal and inhalational toxicity of biocides is limited. We evaluated the effects of biocides on the skin and airways using the reconstructed human epidermis model KeraSkin™ and the airway model SoluAirway™. We determined the irritancy of 11 commonly used biocides (1,2-benzisothiazol-3(2H)-one [BIT], 2-phenoxyethanol [PE], zinc pyrithione, 2-bromo-2-nitropropane-1,3-diol, 3-iodoprop-2-ynyl N-butylcarbamate [IPBC], 2-octyl-1,2-thiazol-3-one, 2,2-dibromo-2-cyanoacetamide, 4-chloro-3-methylphenol [CC], 2-phenylphenol, deltamethrin, and 4,5-dichloro-2-octyl-1,2-thiazol-3-one) in the KeraSkin™ and SoluAirway™ by viability and histological examinations. BIT and CC were found to cause skin irritation at the approved concentrations or at the concentration close to approved limit while the others were non-irritants within the approved concentration. These results were confirmed via histology, wherein skin irritants induced erosion, vacuolation, and necrosis of the tissue. In the SoluAirway™, most of the biocides decreased cell viability even within the approved limits, except for PE, IPBC, and deltamethrin, suggesting that the airway may be more vulnerable to biocides than the skin. Taken together, our result indicates that some biocides can induce toxicity in skin and airway. Further studies on the dermal and inhalational toxicity of biocides are warranted.

Leveraging 3D Model Systems to Understand Viral Interactions with the Respiratory Mucosa

Respiratory viruses remain a significant cause of morbidity and mortality in the human population, underscoring the importance of ongoing basic research into virus-host interactions. However, many critical aspects of infection are difficult, if not impossible, to probe using standard cell lines, 2D culture formats, or even animal models. In vitro systems such as airway epithelial cultures at air-liquid interface, organoids, or 'on-chip' technologies allow interrogation in human cells and recapitulate emergent properties of the airway epithelium-the primary target for respiratory virus infection. While some of these models have been used for over thirty years, ongoing advancements in both culture techniques and analytical tools continue to provide new opportunities to investigate airway epithelial biology and viral infection phenotypes in both normal and diseased host backgrounds. Here we review these models and their application to studying respiratory viruses. Furthermore, given the ability of these systems to recapitulate the extracellular microenvironment, we evaluate their potential to serve as a platform for studies specifically addressing viral interactions at the mucosal surface and detail techniques that can be employed to expand our understanding.

Bridging the gap between traditional cell cultures and bioreactors applied in regenerative medicine: practical experiences with the MINUSHEET perfusion culture system

To meet specific requirements of developing tissues urgently needed in tissue engineering, biomaterial research and drug toxicity testing, a versatile perfusion culture system was developed. First an individual biomaterial is selected and then mounted in a MINUSHEET(®) tissue carrier. After sterilization the assembly is transferred by fine forceps to a 24 well culture plate for seeding cells or mounting tissue on it. To support spatial (3D) development a carrier can be placed in various types of perfusion culture containers. In the basic version a constant flow of culture medium provides contained tissue with always fresh nutrition and respiratory gas. For example, epithelia can be transferred to a gradient container, where they are exposed to different fluids at the luminal and basal side. To observe development of tissue under the microscope, in a different type of container a transparent lid and base are integrated. Finally, stem/progenitor cells are incubated in a container filled by an artificial interstitium to support spatial development. In the past years the described system was applied in numerous own and external investigations. To present an actual overview of resulting experimental data, the present paper was written.

Comparison of human nasal epithelial cells grown as explant outgrowth cultures or dissociated tissue cultures in vitro

The purpose of this study was to compare cell growth characteristics, ciliated cell differentiation, and function of human nasal epithelial cells established as explant outgrowth cultures or dissociated tissue cultures. Human nasal mucosa of the uncinate process was obtained by endoscopy and epithelial cell cultures were established by explant outgrowth or dissociated tissue culture methods. Epithelial cell growth characteristics were observed by inverted phase contrast microscopy. Ciliated cell differentiation was detected by β-tubulin IVand ZO-1 immunocytochemistry. Basal and ATP-stimulated ciliary beat frequency (CBF) was measured using a highspeed digital microscopic imaging system. Both the explant and dissociated tissue cultures established as monolayers with tight junctions and differentiated cell composition, with both types of cultures comprising ciliated and non-ciliated epithelial cells. Fibroblasts were also frequently found in explant cultures but rarely seen in dissociated tissue cultures. In both culture systems, the highest ciliated cell density appeared at 7th-10th culture day and declined with time, with the lifespan of ciliated cells ranging from 14 to 21 days. Overall, 10% of the cells in explant cultures and 20% of the cells in the dissociated tissue cultures were ciliated. These two cultures demonstrated similar ciliary beat frequency values at baseline (7.78 ± 1.99 Hz and 7.91 ± 2.52 Hz, respectively) and reacted equivalently following stimulation with 100 μM ATP. The results of this study indicate that both the explant outgrowth and dissociated tissue culture techniques are suitable for growing well-differentiated nasal ciliated and non-ciliated cells, which have growth characteristics and ciliary activity similar to those of nasal epithelial cells in vivo.

Supportive development of functional tissues for biomedical research using the MINUSHEET® perfusion system

Functional tissues generated under in vitro conditions are urgently needed in biomedical research. However, the engineering of tissues is rather difficult, since their development is influenced by numerous parameters. In consequence, a versatile culture system was developed to respond the unmet needs.

Optimal adhesion for cells in this system is reached by the selection of individual biomaterials. To protect cells during handling and culture, the biomaterial is mounted onto a MINUSHEET® tissue carrier. While adherence of cells takes place in the static environment of a 24 well culture plate, generation of tissues is accomplished in one of several available perfusion culture containers. In the basic version a continuous flow of always fresh culture medium is provided to the developing tissue. In a gradient perfusion culture container epithelia are exposed to different fluids at the luminal and basal sides. Another special container with a transparent lid and base enables microscopic visualization of ongoing tissue development. A further container exhibits a flexible silicone lid to apply force onto the developing tissue thereby mimicking mechanical load that is required for developing connective and muscular tissue. Finally, stem/progenitor cells are kept at the interface of an artificial polyester interstitium within a perfusion culture container offering for example an optimal environment for the spatial development of renal tubules.

The system presented here was evaluated by various research groups. As a result a variety of publications including most interesting applications were published. In the present paper these data were reviewed and analyzed. All of the results point out that the cell biological profile of engineered tissues can be strongly improved, when the introduced perfusion culture technique is applied in combination with specific biomaterials supporting primary adhesion of cells.

Stability and structure of protein-lipoamino acid colloidal particles: toward nasal delivery of pharmaceutically active proteins

To circumvent the painful intravenous injection of proteins in the treatment of children with growth deficiency, anemia, and calcium insufficiency, we investigated the stability and structure of protein-lipoamino acid complexes that could be nasally sprayed. Preparations that ensure a colloidal and structural stability of recombinant human growth hormone (rhGH), recombinant human erythropoietin (rhEPO), and salmon calcitonin (sCT) mixed with lauroyl proline (LP) were established. Protein structure was controlled by circular dichroism, and very small sizes of ca. 5 nm were determined by dynamic light scattering. The colloidal preparations could be sprayed with a droplet size of 20-30 μm. The molecular structure of aggregates was investigated by all-atom molecular dynamics. Whereas a lauroyl proline capping of globular proteins rhGH and rhEPO with preservation of their active structure was observed, a mixed micelle of sCT and lipoamino acids was formed. In the latter, aggregated LP constitutes the inner core and the surface is covered with calcitonins that acquire a marked α-helix character. Hydrophobic/philic interaction balance between proteins and LP drives the particles' stability. Passage through nasal cells grown at confluence was markedly increased by the colloidal preparations and could reach a 20 times increase in the case of EPO. Biological implications of such colloidal preparations are discussed in terms of furtiveness.

An improved primary human nasal cell culture for the simultaneous determination of transepithelial transport and ciliary beat frequency

Objectives

The aim was to establish a preclinical in-vitro system of the nasal mucosa for the simultaneous evaluation of nasal absorption and effects on ciliary activity.

Methods

Human nasal epithelial cells were grown in collagen-coated transport inserts with transparent polyethylene terephthalate membranes (3 μm). Transepithelial transport and ciliary beat frequency values were measured every 15 min for 1 h.

Key findings

The apparent permeability coefficients (Papp) for atenolol (mainly paracellular transport) and propranolol (transcellular transport) amounted to 0.1 ± 0.1 and 23.7 ± 0.6 × 10−6 cm/s, respectively, illustrating that the system can be used to discriminate between high permeability and low permeability compounds. Transport of talinolol (substrate for the P-glycoprotein efflux carrier) did not reveal polarity (0.3 ± 0.2 and 0.2 ± 0.1 × 10−6 cm/s for absorptive and secretory transport, respectively) and was not affected by verapamil (10 μm), suggesting the absence of P-glycoprotein in the nasal cell culture. No significant effects of atenolol, propranolol and talinolol on ciliary beat frequency were observed (98 ± 20% of the control condition after 60 min). Chlorocresol significantly decreased the ciliary activity but this decrease was not accompanied by effects on the transepithelial transport of atenolol, propranolol and talinolol.

Conclusions

A new system was developed which offers possibilities as a fast screening tool for studying the potential of compounds for nasal drug administration, since permeability and a possible cilio-toxic effect can be assessed simultaneously.

High-speed digital imaging method for ciliary beat frequency measurement

The aim of this study was to develop a high-speed digital imaging system and related software for ciliary beat frequency (CFB) analysis in order to establish an automated and reliable method that is observer independent and faster compared to the conventional computerized microscope photometry method. Using primary human nasal epithelial cell cultures, the CBF was recorded with a computerized microscope photometry system and a high-speed digital imaging system. To obtain a wide range of frequencies, glycocholate (0.5%) and chlorocresol (0.005%) were used as ciliostimulatory and cilio-inhibitory reference compounds, respectively. The mean values in hertz (+/- s.d.) obtained with the photometry and high-speed digital imaging systems were: controls 8.2 +/- 0.9 and 7.9 +/- 1.1; chlorocresol 5.0 +/- 0.9 and 5.1 +/- 1.1; glycocholate 9.8 +/- 1.0 and 9.7 +/- 0.8. A similar increase (by 20 and 24%) and decrease (by 38 and 35%) in CBF was determined by the two methods after glycocholate and chlorocresol treatment, respectively. The mean difference between the photometry and high-speed digital imaging methods was 0.2 +/- 0.6 Hz, and the Bland-Altman limits of agreement were from -1.0 to +1.4 Hz, suggesting that the results obtained by these two methods could be used interchangeably. These results show the reliability of the high-speed digital imaging system and the software developed for in-vitro CBF measurements. The advantages of the system include: (i) fast data acquisition and calculation, (ii) whole field automated CBF analysis and (iii) reduction in selection bias.