Human normal bronchial epithelial cells: a novel in vitro cell model for toxicity evaluation

Antimicrobials: An update on new strategies to diversify treatment for bacterial infections

Ninety-five years after Fleming's discovery of penicillin, a bounty of antibiotic compounds have been discovered, modified, or synthesised. Diversification of target sites, improved stability and altered activity spectra have enabled continued antibiotic efficacy, but overwhelming reliance and misuse has fuelled the global spread of antimicrobial resistance (AMR). An estimated 1.27 million deaths were attributable to antibiotic resistant bacteria in 2019, representing a major threat to modern medicine. Although antibiotics remain at the heart of strategies for treatment and control of bacterial diseases, the threat of AMR has reached catastrophic proportions urgently calling for fresh innovation. The last decade has been peppered with ground-breaking developments in genome sequencing, high throughput screening technologies and machine learning. These advances have opened new doors for bioprospecting for novel antimicrobials. They have also enabled more thorough exploration of complex and polymicrobial infections and interactions with the healthy microbiome. Using models of infection that more closely resemble the infection state in vivo, we are now beginning to measure the impacts of antimicrobial therapy on host/microbiota/pathogen interactions. However new approaches are needed for developing and standardising appropriate methods to measure efficacy of novel antimicrobial combinations in these contexts. A battery of promising new antimicrobials is now in various stages of development including co-administered inhibitors, phages, nanoparticles, immunotherapy, anti-biofilm and anti-virulence agents. These novel therapeutics need multidisciplinary collaboration and new ways of thinking to bring them into large scale clinical use.

Morphologically and karyotypically atypical cells of 'normal' human bronchial epithelial cell line (Beas-2B)

Beas-2B is an adenovirus 12-SV40-transfected cell line of "normal" human bronchial epithelial cells. This cell line was able to replace normal human bronchial epithelial cells, which are currently unavailable, and served as a model for related studies in numerous toxicology and cancer transformation experiments. In any experiment involving toxins or carcinogens, the basic morphology of Beas-2B should be well characterized prior to exposure, but this has never been properly reported. In this study, atypical cells of the Beas-2B cell line in early passage culture were observed using light and electron microscopy, and the cells were further investigated for abnormal karyotypes by flow cytometry. This Beas-2B cell line could be morphologically categorized into two cell types, A and B. Type A contains a large nucleus and abundant cytoplasm (type A > 95%) and type B contains a small nucleus with dense and scarce cytoplasm (type B < 5%). Both atypical cell types had atypical and multilobed/multinucleated cells, including a high percentage (>30%) of mitotic figures, and were Ki-67 positive (100%). Karyotyping also revealed that 40.4% of the cells had atypical karyotyped chromosomes. In light of these findings, this cell line is no longer a "normal" cell, and experiments performed using this cell line can be questioned for non-default results. Experimenters should consider this error in future experiments.

Cellular heterogeneity in the 16HBE14o- airway epithelial line impacts biological readouts

The airway epithelial cell line, 16HBE14o- , is an important cell model for studying airway disease. 16HBE14o- cells were originally generated from primary human bronchial epithelial cells by SV40-mediated immortalization, a process that is associated with genomic instability through long-term culture. Here, we explore the heterogeneity of these cells, with respect to expression of the cystic fibrosis transmembrane conductance regulator (CFTR) transcript and protein. We isolate clones of 16HBE14o- with stably higher and lower levels of CFTR in comparison to bulk 16HBE14o- , designated CFTRhigh and CFTRlow . Detailed characterization of the CFTR locus in these clones by ATAC-seq and 4C-seq showed open chromatin profiles and higher order chromatin structure that correlate with CFTR expression levels. Transcriptomic profiling of CFTRhigh and CFTRlow cells showed that the CFTRhigh cells had an elevated inflammatory/innate immune response phenotype. These results encourage caution in interpreting functional data from clonal lines of 16HBE14o- cells, generated after genomic or other manipulations.

Treating intrauterine adhesion using conditionally reprogrammed physiological endometrial epithelial cells

Background

There is unmet need for effective therapies of intrauterine adhesions (IUAs) that are common cause of menstrual disturbance and infertility, since current clinical procedures do not improve prognosis for patients with moderate to severe IUA, with a recurrence rate of 23–50%. Stem cell-based therapy has emerged as a therapeutic option with unsolved issues for IUA patients in the past few years. Primary endometrial epithelial cells for cell therapy are largely hampered with the extremely limited proliferation capacity of uterine epithelial cells. This study was to evaluate whether IUA is curable with conditionally reprogrammed (CR) endometrial epithelial cells.

Methods

Mouse endometrial epithelial cells (MEECs) were isolated from C57BL female mice, and long-term cultures of MEECs were established and maintained with conditional reprogramming (CR) method. DNA damage response analysis, soft agar assay, and matrigel 3D culture were carried out to determine the normal biological characteristics of CR-MEECs. The tissue-specific differentiation potential of MEECs was analyzed with air–liquid interface (ALI) 3D culture, hematoxylin and eosin (H&E) staining, Masson’s trichrome and DAB staining, immunofluorescence assay. IUA mice were constructed and transplanted with CR-MEECs. Repair and mechanisms of MEECs transplantation in IUA mice were measured with qRT-PCR, Masson’s trichrome, and DAB staining.

Results

We first successfully established long-term cultures of MEECs using CR approach. CR-MEECs maintained a rapid and stable proliferation in this co-culture system. Our data confirmed that CR-MEECs retained normal biological characteristics and endometrium tissue-specific differentiation potential. CR-MEECs also expressed estrogen and progesterone receptors and maintained the exquisite sensitivity to sex hormones in vitro. Most importantly, allogeneic transplantation of CR-MEECs successfully repaired the injured endometrium and significantly improved the pregnancy rate of IUA mice.

Conclusions

Conditionally reprogrammed physiological endometrial epithelial cells provide a novel strategy in IUA clinics in a personalized or generalized manner and also serve as a physiological model to explore biology of endometrial epithelial cells and mechanisms of IUA.

Chromium [Cr(VI)] Exposure Causes Cytotoxicity of Human Bronchial Epithelial Cells (16-HBE) and Proteomic Alterations

Hexavalent chromium [Cr(VI)] is a common industrial pollutant, and exposure may cause toxic effects in multiple organ systems and carcinogenesis, including lung cancer. However, the toxic effect of Cr(VI) on the respiratory system is poorly understood. In the present study, it was demonstrated that Cr(VI) exposure significantly decreased the viability of human bronchial epithelial cells (16-HBE) in a dose-dependent manner. Flow cytometry demonstrated that Cr(VI) enhanced the transition of 16-HBE cells from G₁ to S phase and arrested S-phase progression. Reverse transcription-quantitative polymerase chain reaction analysis revealed a significant alteration in the expression of apoptosis-associated genes in Cr(VI)-treated 16-HBE cells. In addition, using two-dimensional fluorescence differential gel electrophoresis with mass spectrometry, 15 differentially expressed proteins (1 upregulated and 14 downregulated) were identified in 16-HBE cells with Cr(VI) treatment compared with controls. Functional classification revealed that these differentially expressed proteins were involved in apoptosis, cytoskeletal structure, and energy metabolism. In conclusion, these data suggested that Cr(VI) caused toxic effects in bronchial epithelial cells and the mechanisms may involve the abnormal expression of apoptosis-associated proteins, cytoskeletal proteins, and energy metabolism-associated proteins.

Exposure Effects Beyond the Epithelial Barrier: Transepithelial Induction of Oxidative Stress by Diesel Exhaust Particulates in Lung Fibroblasts in an Organotypic Human Airway Model

In vitro bronchial epithelial monoculture models have been pivotal in defining the adverse effects of inhaled toxicant exposures; however, they are only representative of one cellular compartment and may not accurately reflect the effects of exposures on other cell types. Lung fibroblasts exist immediately beneath the bronchial epithelial barrier and play a central role in lung structure and function, as well as disease development and progression. We tested the hypothesis that in vitro exposure of a human bronchial epithelial cell barrier to the model oxidant diesel exhaust particulates caused transepithelial oxidative stress in the underlying lung fibroblasts using a human bronchial epithelial cell and lung fibroblast coculture model. We observed that diesel exhaust particulates caused transepithelial oxidative stress in underlying lung fibroblasts as indicated by intracellular accumulation of the reactive oxygen species hydrogen peroxide, oxidation of the cellular antioxidant glutathione, activation of NRF2, and induction of oxidative stress-responsive genes. Further, targeted antioxidant treatment of lung fibroblasts partially mitigated the oxidative stress response gene expression in adjacent human bronchial epithelial cells during diesel exhaust particulate exposure. This indicates that exposure-induced oxidative stress in the airway extends beyond the bronchial epithelial barrier and that lung fibroblasts are both a target and a mediator of the adverse effects of inhaled chemical exposures despite being separated from the inhaled material by an epithelial barrier. These findings illustrate the value of coculture models and suggest that transepithelial exposure effects should be considered in inhalation toxicology research and testing.

Epithelial barrier function properties of the 16HBE14o- human bronchial epithelial cell culture model

The human bronchial epithelial cell line, 16HBE14o- (16HBE), is widely used as a model for respiratory epithelial diseases and barrier function. During differentiation, transepithelial electrical resistance (TER) increased to approximately 800 Ohms × cm², while ¹⁴C-d-mannitol flux rates (J_m) simultaneously decreased. Tight junctions (TJs) were shown by diffusion potential studies to be anion-selective with P_C1/P_Na = 1.9. Transepithelial leakiness could be induced by the phorbol ester, protein kinase C (PKC) activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), and the proinflammatory cytokine, tumor necrosis factor-α (TNF-α). Basal barrier function could not be improved by the micronutrients, zinc, or quercetin. Of methodological significance, TER was observed to be more variable and to spontaneously, significantly decrease after initial barrier formation, whereas J_m did not significantly fluctuate or increase. Unlike the strong inverse relationship between TER and J_m during differentiation, differentiated cell layers manifested no relationship between TER and J_m. There was also much greater variability for TER values compared with J_m. Investigating the dependence of 16HBE TER on transcellular ion conductance, inhibition of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) chloride channel with GlyH-101 produced a large decrease in short-circuit current (I_sc) and a slight increase in TER, but no significant change in J_m. A strong temperature dependence was observed not only for I_sc, but also for TER. In summary, research utilizing 16HBE as a model in airway barrier function studies needs to be aware of the complexity of TER as a parameter of barrier function given the influence of CFTR-dependent transcellular conductance on TER.

From Submerged Cultures to 3D Cell Culture Models: Evolution of Nasal Epithelial Cells in Asthma Research and Virus Infection

Understanding the response to viral infection in the context of respiratory diseases is of significant importance. Recently, there has been more focus on the role of the nasal epithelium in disease modeling. Here, we provide an overview of different submerged, organotypic 3D and spheroid cell culture models of nasal epithelial cells, which were used to study asthma and allergy with a special focus on virus infection. In detail, this review summarizes the importance, benefits, and disadvantages of patient-derived cell culture models of nasal- and bronchial epithelial cells, including a comparison of these cell culture models and a discussion on why investigators should consider using nasal epithelial cells in their research. Exposure experiments, simple virus transduction analyses as well as genetic studies can be performed in these models, which may provide first insights into the complexity of molecular signatures and may open new doors for drug discovery and biomarker research.

Retinoic acid improves baseline barrier function and attenuates TNF-α-induced barrier leak in human bronchial epithelial cell culture model, 16HBE 14o

Retinoic acid (RA) has been shown to improve epithelial and endothelial barrier function and development and even suppress damage inflicted by inflammation on these barriers through regulating immune cell activity. This paper thus sought to determine whether RA could improve baseline barrier function and attenuate TNF-α-induced barrier leak in the human bronchial epithelial cell culture model, 16HBE14o- (16HBE). We show for the first time that RA increases baseline barrier function of these cell layers indicated by an 89% increase in transepithelial electrical resistance (TER) and 22% decrease in ¹⁴C-mannitol flux. A simultaneous, RA-induced 70% increase in claudin-4 attests to RA affecting the tight junctional (TJ) complex itself. RA was also effective in alleviating TNF-α-induced 16HBE barrier leak, attenuating 60% of the TNF-α-induced leak to ¹⁴C-mannitol and 80% of the leak to ¹⁴C-inulin. Interleukin-6-induced barrier leak was also reduced by RA. Treatment of 16HBE cell layers with TNF-α resulted in dramatic decrease in immunostaining for occludin and claudin-4, as well as a downward “band-shift” in occludin Western immunoblots. The presence of RA partially reversed TNF-α’s effects on these select TJ proteins. Lastly, RA completely abrogated the TNF-α-induced increase in ERK-1,2 phosphorylation without significantly decreasing the TNF-driven increase in total ERK-1,2. This study suggests RA could be effective as a prophylactic agent in minimizing airway barrier leak and as a therapeutic in preventing leak triggered by inflammatory cascades. Given the growing literature suggesting a “cytokine storm” may be related to COVID-19 morbidity, RA may be a useful adjuvant for use with anti-viral therapies.

Conditional cell reprogramming for modeling host-virus interactions and human viral diseases

Conventional cancer and transformed cell lines are widely used in cancer biology and other fields within biology. These cells usually have abnormalities from the original tumor itself, but may also develop abnormalities due to genetic manipulation, or genetic and epigenetic changes during long-term passages. Primary cultures may maintain lineage functions as the original tissue types, yet they have a very limited life span or population doubling time because of the nature of cellular senescence. Primary cultures usually have very low yields, and the high variability from any original tissue specimens, largely limiting their applications in research. Animal models are often used for studies of virus infections, disease modeling, development of antiviral drugs, and vaccines. Human viruses often need a series of passages in vivo to adapt to the host environment because of variable receptors on the cell surface and may have intracellular restrictions from the cell types or host species. Here, we describe a long-term cell culture system, conditionally reprogrammed cells (CRCs), and its applications in modeling human viral diseases and drug discovery. Using feeder layer coculture in presence of Y-27632 (conditional reprogramming, CR), CRCs can be obtained and rapidly propagated from surgical specimens, core or needle biopsies, and other minimally invasive or noninvasive specimens, for example, nasal cavity brushing. CRCs preserve their lineage functions and provide biologically relevant and physiological conditions, which are suitable for studies of viral entry and replication, innate immune responses of host cells, and discovery of antiviral drugs. In this review, we summarize the applications of CR technology in modeling host-virus interactions and human viral diseases including severe acute respiratory syndrome coronavirus-2 and coronavirus disease-2019, and antiviral discovery.

Coupled CRC 2D and ALI 3D Cultures Express Receptors of Emerging Viruses and Are More Suitable for the Study of Viral Infections Compared to Conventional Cell Lines

Infections of emerging and reemerging viruses (SARS-CoVs, influenza H1N1, etc.) largely and globally affect human health. Animal models often fail to reflect a physiological status because of species tropism of virus infection. Conventional cell lines are usually genetically and phenotypically different from primary cells. Developing an in vitro physiological model to study the infection of emerging viruses will facilitate our understanding of virus-host cell interactions, thereby benefiting antiviral drug discovery. In the current work, we first established normal airway epithelial cells (upper and lower airway track) in 2D and 3D culture systems using conditional reprogramming (CR) and air-liquid interface (ALI) techniques. These long-term cultures maintained differentiation potential. More importantly, these cells express two types of influenza virus receptors, α2-6-Gal- and α2-3-Gal-linked sialic acids, and angiotensin-converting enzyme 2 (ACE2), a receptor for SARS-CoVs as well. These cells were permissive to the infection of pandemic influenza H1N1 (H1N1pdm). In contrast, the lung cancer cell line A549 and immortalized airway epithelial cells (16HBE) were not susceptible to H1N1 infection. A virus-induced cytopathic effect (CPE) on 2D CRC cultures developed in a time-dependent manner. The pathological effects were also readily observed spreading from the apical layer to the basal layer of the 3D ALI culture. This integrated 2D CRC and 3D ALI cultures provide a physiological and personalized in vitro model to study the infection of emerging viruses. This novel model can be used for studying virus biology and host response to viral infection and for antiviral drug discovery.

Transient receptor potential canonical 1 channel mediates the mechanical stress‑induced epithelial‑mesenchymal transition of human bronchial epithelial (16HBE) cells

Airway remodeling is a central event in the pathology of chronic obstructive pulmonary disease (COPD) that leads to airway narrowing and subsequently, to increased mechanical pressure. High mechanical pressure can exacerbate airway remodeling. Thus, a treatment regimen aimed at disrupting this high‑pressure airway remodeling vicious cycle may improve the prognosis of patients with COPD. Recent studies have demonstrated that mechanical stress induces lung epithelial‑mesenchymal transition (EMT), which is commonly present in airway epithelial cells of patients with COPD. As TRPC1 functions as a mechanosensitive channel that mediates non‑selective cation entry in response to increased membrane stretch, the present study investigated the role of TRPC1 in the occurrence of EMT induced by mechanical stress. In the present study, the expression of TRPC1 in the bronchial epithelium was examined in vivo by immunohistochemistry. In vitro, human bronchial epithelial (16HBE) cells were subjected to mechanical stretching for up to 48 h, and TRPC1 expression was then examined by RT‑qPCR and western blot analysis. In addition, TRPC1 receptor function was assessed by Ca2+ imaging and siRNA transfection. EMT was identified using immunofluorescence, western blot analysis and RT‑qPCR. It was found that TRPC1 expression was upregulated in patients with COPD and in 16HBE cells subjected to mechanical stretch. The mechanical stress‑induced activation of TRPC1 in 16HBE cells increased the intracellular calcium concentration and subsequently decreased the expression of cytokeratin 8 and E‑cadherin, and increased the expression of α‑smooth muscle actin, indicating the occurrence of EMT. On the whole, the findings of the present study demonstrate that TRPC1 plays a key role in the occurrence of EMT in human lung epithelial cells in response to mechanical stretch; thus, this protein may serve as a novel therapeutic target for progressive airway remodeling in COPD.

Long Term Culture of Human Kidney Proximal Tubule Epithelial Cells Maintains Lineage Functions and Serves as an Ex vivo Model for Coronavirus Associated Kidney Injury

The mechanism of how SARS-CoV-2 causes severe multi-organ failure is largely unknown. Acute kidney injury (AKI) is one of the frequent organ damage in severe COVID-19 patients. Previous studies have shown that human renal tubule cells could be the potential host cells targeted by SARS-CoV-2. Traditional cancer cell lines or immortalized cell lines are genetically and phenotypically different from host cells. Animal models are widely used, but often fail to reflect a physiological and pathogenic status because of species tropisms. There is an unmet need for normal human epithelial cells for disease modeling. In this study, we successfully established long term cultures of normal human kidney proximal tubule epithelial cells (KPTECs) in 2D and 3D culture systems using conditional reprogramming (CR) and organoids techniques. These cells had the ability to differentiate and repair DNA damage, and showed no transforming property. Importantly, the CR KPTECs maintained lineage function with expression of specific transporters (SLC34A3 and cubilin). They also expressed angiotensin-converting enzyme 2 (ACE2), a receptor for SARS-CoV and SARS-CoV-2. In contrast, cancer cell line did not express endogenous SLC34A3, cubilin and ACE2. Very interestingly, ACE2 expression was around twofold higher in 3D organoids culture compared to that in 2D CR culture condition. Pseudovirion assays demonstrated that SARS-CoV spike (S) protein was able to enter CR cells with luciferase reporter. This integrated 2D CR and 3D organoid cultures provide a physiological ex vivo model to study kidney functions, innate immune response of kidney cells to viruses, and a novel platform for drug discovery and safety evaluation.

Conditionally Reprogrammed Human Normal Airway Epithelial Cells at ALI: A Physiological Model for Emerging Viruses

Cancer cell lines have been used widely in cancer biology, and as biological or functional cell systems in many biomedical research fields. These cells are usually defective for many normal activities or functions due to significant genetic and epigenetic changes. Normal primary cell yields and viability from any original tissue specimens are usually relatively low or highly variable. These normal cells cease after a few passages or population doublings due to very limited proliferative capacity. Animal models (ferret, mouse, etc.) are often used to study virus-host interaction. However, viruses usually need to be adapted to the animals by several passages due to tropism restrictions including viral receptors and intracellular restrictions. Here we summarize applications of conditionally reprogrammed cells (CRCs), long-term cultures of normal airway epithelial cells from human nose to lung generated by conditional cell reprogramming (CR) technology, as an ex vivo model in studies of emerging viruses. CR allows to robustly propagate cells from non-invasive or minimally invasive specimens, for example, nasal or endobronchial brushing. This process is rapid (2 days) and conditional. The CRCs maintain their differentiation potential and lineage functions, and have been used for studies of adenovirus, rhinovirus, respiratory syncytial virus, influenza viruses, parvovirus, and SARS-CoV. The CRCs can be easily used for air-liquid interface (ALI) polarized 3D cultures, and these coupled CRC/ALI cultures mimic physiological conditions and are suitable for studies of viral entry including receptor binding and internalization, innate immune responses, viral replications, and drug discovery as an ex vivo model for emerging viruses.

TRPC6-dependent Ca2+ signaling mediates airway inflammation in response to oxidative stress via ERK pathway

Ozone (O₃) plays an extremely important role in airway inflammation by generating reactive oxygen species (ROS) including hydrogen peroxide, then promoting redox actions and causing oxidative stress. Evidences indicate that TRPC6 (canonical transient receptor potential channel 6) is a redox-regulated Ca²⁺ permeable nonselective cation channel, but its role in the setting of oxidative stress-related airway inflammation remains unknown. Here, we found that both TRPC6^-/- mice and mice pretreated with SAR7334, a potent TRPC6 inhibitor, were protected from O₃-induced airway inflammatory responses. In vitro, both knockdown of TRPC6 expression with shRNA and TRPC6 blockage markedly attenuated the release of cytokines IL-6 and IL-8 induced by O₃ or H₂O₂ in 16HBE cells (human bronchial epithelial cell line). Treatment with O₃ or H₂O₂ enhanced TRPC6 protein expression in vivo and vitro. We also observed that TRPC6-dependent increase of intracellular Ca²⁺ concentration ([Ca²⁺]_i) was triggered by H₂O₂, which consisted of the release from intracellular calcium store and the influx of extracellular Ca²⁺ and could be further strengthened by 6-h O₃ exposure in both 16HBE cells and HBEpiCs (primary human bronchial epithelial cells). Moreover, we confirmed that the activation of MAPK signals (ERK1/2, p38, JNK) was required for the inflammatory response induced by O₃ or H₂O₂ while only the phosphorylation of ERK pathway was diminished in the TRPC6-knockdown situation. These results demonstrate that oxidative stress regulates TRPC6-mediated Ca²⁺ cascade, which leads to the activation of ERK pathway and inflammation and could become a potential target to treat oxidative stress-associated airway inflammatory diseases.

Hyaluronan Graft Copolymers Bearing Fatty-Acid Residues as Self-Assembling Nanoparticles for Olanzapine Delivery

In order to evaluate the potential of a technology platform based on hyaluronan copolymers grafted with propargylated ferulate fluorophores (HA-FA-Pg) in the development of drug delivery systems, the propargyl groups of HA-FA-Pg derivatives were employed with oleic acid (OA) or stearic acid (SA) residues across a biocompatible hexa(ethylene glycol) (HEG) spacer. The designed materials (i.e., HA-FA-HEG-OA or HA-FA-HEG-SA) showed clear-cut aggregation features in an aqueous environment, as confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM), generating nanoaggregate systems. In fact, HA-FA-HEG-OA and HA-FA-HEG-SA derivatives showed the property to create self-assembled cytocompatible nanostructured aggregates in water, thanks to the simultaneous presence of hydrophilic portions in the polymeric backbone, such as hyaluronic acid, and hydrophobic portions in the side chains. Furthermore, the designed materials interact with living cells showing a high degree of cytocompatibility. The potential ability of nanosystems to load pharmacologically active molecules was assessed by the physical entrapment of olanzapine into both polymeric systems. The drug loading evaluation demonstrated that the nanoparticles are able to incorporate a good quantity of olanzapine, as well as improve drug solubility, release profile, and cytocompatibility.

Toxicological effects of ambient fine (PM2.5-0.18) and ultrafine (PM0.18) particles in healthy and diseased 3D organo-typic mucocilary-phenotype models

The knowledge of the underlying mechanisms by which particulate matter (PM) exerts its health effects is still incomplete since it may trigger various symptoms as some persons may be more susceptible than others. Detailed studies realized in more relevant in vitro models are highly needed. Healthy normal human bronchial epithelial (NHBE), asthma-diseased human bronchial epithelial (DHBE), and COPD-DHBE cells, differentiated at the air-liquid interface, were acutely or repeatedly exposed to fine (i.e., PM_2.5-0.18, also called FP) and quasi-ultrafine (i.e., PM_0.18, also called UFP) particles. Immunofluorescence labelling of pan-cytokeratin, MUC5AC, and ZO-1 confirmed their specific cell-types. Baselines of the inflammatory mediators secreted by all the cells were quite similar. Slight changes of TNFα, IL-1β, IL-6, IL-8, GM-CSF, MCP-1, and/or TGFα, and of H3K9 histone acetylation supported a higher inflammatory response of asthma- and especially COPD-DHBE cells, after exposure to FP and especially UFP. At baseline, 35 differentially expressed genes (DEG) in asthma-DHBE, and 23 DEG in COPD-DHBE, compared to NHBE cells, were reported. They were involved in biological processes implicated in the development of asthma and COPD diseases, such as cellular process (e.g., PLA2G4C, NLRP1, S100A5, MUC1), biological regulation (e.g., CCNE1), developmental process (e.g., WNT10B), and cell component organization and synthesis (e.g., KRT34, COL6A1, COL6A2). In all the FP or UFP-exposed cell models, DEG were also functionally annotated to the chemical metabolic process (e.g., CYP1A1, CYP1B1, CYP1A2) and inflammatory response (e.g., EREG). Another DEG, FGF-1, was only down-regulated in asthma and specially COPD-DHBE cells repeatedly exposed. While RAB37 could help to counteract the down-regulation of FGF-1 in asthma-DHBE cells, the deregulation of FGR, WNT7B, VIPR1, and PPARGC1A could dramatically contribute to make it worse in COPD-DHBE cells. Taken together, these data contributed to support the highest effects of UFP versus FP and highest sensitivity of asthma- and notably COPD-DHBE versus NHBE cells.

Ex vivo 2D and 3D HSV-2 infection model using human normal vaginal epithelial cells

Herpes simplex virus type 2 (HSV-2) infects human genital mucosa and establishes life-long latent infection. It is unmet need to establish a human cell-based microphysiological system for virus biology and anti-viral drug discovery. One of barriers is lacking of culture system of normal epithelial cells in vitro over decades. In this study, we established human normal vaginal epithelial cell (HNVEC) culture using co-culture system. HNVEC cells were then propagated rapidly and stably in a defined culture condition. HNVEC cells exhibited a normal diploid karyotype and formed the well-defined and polarized spheres in matrigel three-dimension (3D) culture, while malignant cells (HeLa) formed disorganized and nonpolar solid spheres. HNVEC cells had a normal cellular response to DNA damage and had no transforming property using soft agar assays. HNVEC expressed epithelial marker cytokeratin 14 (CK14) and p63, but not cytokeratin 18 (CK18). Next, we reconstructed HNVEC-derived 3D vaginal epithelium using air-liquid interface (ALI) culture. This 3D vaginal epithelium has the basal and apical layers with expression of epithelial markers as its originated human vaginal tissue. Finally, we established an HSV-2 infection model based on the reconstructed 3D vaginal epithelium. After inoculation of HSV-2 (G strain) at apical layer of the reconstructed 3D vaginal epithelium, we observed obvious pathological effects gradually spreading from the apical layer to basal layer with expression of a viral protein. Thus, we established an ex vivo 2D and 3D HSV-2 infection model that can be used for HSV-2 virology and anti-viral drug discovery.

Choose your cell model wisely: The in vitro nanoneurotoxicity of differentially coated iron oxide nanoparticles for neural cell labeling

Currently, there is a large interest in the labeling of neural stem cells (NSCs) with iron oxide nanoparticles (IONPs) to allow MRI-guided detection after transplantation in regenerative medicine. For such biomedical applications, excluding nanotoxicity is key. Nanosafety is primarily evaluated in vitro where an immortalized or cancer cell line of murine origin is often applied, which is not necessarily an ideal cell model. Previous work revealed clear neurotoxic effects of PMA-coated IONPs in distinct cell types that could potentially be applied for nanosafety studies regarding neural cell labeling. Here, we aimed to assess if DMSA-coated IONPs could be regarded as a safer alternative for this purpose and how the cell model impacted our nanosafety optimization study. Hereto, we evaluated cytotoxicity, ROS production, calcium levels, mitochondrial homeostasis and cell morphology in six related neural cell types, namely neural stem cells, an immortalized cell line and a cancer cell line from human and murine origin. The cell lines mostly showed similar responses to both IONPs, which were frequently more pronounced for the PMA-IONPs. Of note, ROS and calcium levels showed opposite trends in the human and murine NSCs, indicating the importance of the species. Indeed, the human cell models were overall more sensitive than their murine counterpart. Despite the clear cell type-specific nanotoxicity profiles, our multiparametric approach revealed that the DMSA-IONPs outperformed the PMA-IONPs in terms of biocompatibility in each cell type. However, major cell type-dependent variations in the observed effects additionally warrant the use of relevant human cell models.

STATEMENT OF SIGNIFICANCE

Inorganic nanoparticle (NP) optimization is chiefly performed in vitro. For the optimization of iron oxide (IO)NPs for neural stem cell labeling in the context of regenerative medicine human or rodent neural stem cells, immortalized or cancer cell lines are applied. However, the use of certain cell models can be questioned as they phenotypically differ from the target cell. The impact of the neural cell model on nanosafety remains relatively unexplored. Here we evaluated cell homeostasis upon exposure to PMA- and DMSA-coated IONPs. Of note, the DMSA-IONPs outperformed the PMA-IONPs in each cell type. However, distinct cell type-specific effects were witnessed, indicating that nanosafety should be evaluated in a human cell model that represents the target cell as closely as possible.