Maximizing the relevance and reproducibility of A549 cell culture using FBS-free media

In vitroinflammatory and cytotoxic responses of human alveolar cells to amorphous silica nanoparticles exposure

Silicon dioxide nanoparticles (SiO2NPs) are widely used to manufacture products for human consumption. However, their large-scale use in many fields poses risks to industrial workers. In this study, we investigated the cytotoxic and inflammatory potential of SiO2NPs in the human cell line A549, representing the human alveolar epithelium. The NPs were characterized using energy-dispersive x-ray spectroscopy coupled with scanning electron microscopy, x-ray diffraction, transmission electron microscopy, dispersion, and dynamic light scattering. The effects on A549 cells were monitored by cell adhesion and proliferation using electrical impedance, as well as cell viability, apoptosis, necrosis, and secretion of multiple inflammatory mediators. SiO2NPs did not alter the adhesion and proliferation of A549 cells but led to cell death by apoptosis at the highest concentrations tested. SiO2NP impacted the secretion of pro-inflammatory (tumor necrosis factor-α, interleukin (IL)-8, monocyte chemoattractant protein-1, eotaxin, regulated upon activation, normal T cell expressed and secreted, vascular growth factor, granulocyte-macrophage colony-stimulating factor, and granulocyte-colony stimulating factor) and anti-inflammatory (IL-1ra and IL-10) mediators. These results indicate that, even with little impact on cell viability, SiO2NPs can represent a silent danger, owing to their influence on inflammatory mediator secretion and unbalanced local homeostasis.

Humanising nanotoxicology: replacement of animal-derived products in the application of integrated approaches to testing and assessment of nanomaterial inhalation hazard

Over the past decade, the development of nanomaterials (NMs) has surged, highlighting their potential benefits across multiple industries. However, concerns regarding human and environmental exposure remain significant. Traditional in vivo models for safety assessments are increasingly viewed as unfeasible and unethical due to the diverse forms and biological effects of NMs. This has prompted the design of Novel Approach Methods (NAMs) to streamline risk assessment and predict human hazards without relying on animal testing. A critical aspect of advancing NAMs is the urgent need to replace animal-derived products in assay protocols. Incorporating human or synthetic alternatives can significantly reduce the ethical burden of animal use while enhancing the relevance of toxicity testing. This study evaluates the impact of removing animal-derived products from standard acellular and in vitro assays recommended in a published Integrated Approaches to Testing and Assessment (IATA) for inhaled NMs. We specifically assessed the effects of replacing fetal bovine serum with human platelet lysate in acellular reactivity tests and in vitro toxicity testing using a panel of well-characterized NMs. Significant differences in acellular NM reactivity and dramatic changes in A549 cell growth rates and responses to NMs were observed under different media conditions. Our findings demonstrate that variations in experimental setup can fundamentally impact NM hazard assessment, influencing the interpretation of results within specific assays and across tiered testing strategies. Further investigation is needed to support a shift toward more ethical toxicity testing that does not rely on animal-derived materials.

Extracellular Vesicle-based Delivery of Paclitaxel to Lung Cancer Cells: Uptake, Anticancer Effects, Autophagy and Mitophagy Pathways

BACKGROUND

Due to their unique properties, extracellular vesicles (EVs) are promising nanocarriers for exogenous drug delivery.

AIM

We prepared a drug delivery system based on large EVs (LEVs) containing paclitaxel (PTX) (LEVs-PTX) to investigate anticancer effects on lung cancer cells with a focus on autophagy.

METHODS

LEVs-PTX were isolated from lung cancer cells by ultracentrifugation and characterized using different techniques. Rhodamine B dye (Rh B) was used to label LEVs-PTX for cell tracking. MTT assay was performed to investigate the cellular toxicity of PTX and LEVs-PTX for 24 h and 48 h. The uptake of LEVs-PTX was monitored by immunofluorescence microscopy in breast and lung cancer cells. A colorimetric assay was performed to evaluate apoptosis, while Western blotting assays were used to investigate autophagy proteins. Real-time PCR was used to measure mitophagy genes.

RESULTS

Characterization techniques showed that LEVs were isolated and loaded with PTX. Rh B labeled LEVs, which was confirmed by a fluorescence spectrophotometer. Immunofluorescence microscopy showed that the lung and breast cancer cells had captured LEVs. Cell viability was decreased in LEVs-PTX cells which coincided with an increase in caspase-3 activity in LEVs-PTX cells. The Beclin-1 protein level and LC3 II/I ratio decreased, while the P62 protein level was increased in LEVs-PTX cells. The mitophagy genes such as Pink-1 and Parkin were upregulated in LEVs-PTX cells.

CONCLUSION

The data show that LEVs-PTX induced apoptosis, which inhibited the autophagy pathway and increased mitophagy markers, suggesting damage to cell organelles through intracellular delivery of PTX.

Two- and Three-Dimensional Culture Systems: Respiratory In Vitro Tissue Models for Chemical Screening and Risk-Based Decision Making

Risk of lung damage from inhaled chemicals or substances has long been assessed using animal models. However, New Approach Methodologies (NAMs) that replace, reduce, and/or refine the use of animals in safety testing such as 2D and 3D cultures are increasingly being used to understand human-relevant toxicity responses and for the assessment of hazard identification. Here we review 2D and 3D lung models in terms of their application for inhalation toxicity assessment. We highlight a key case study for the Organization for Economic Cooperation and Development (OECD), in which a 3D model was used to assess human toxicity and replace the requirement for a 90-day inhalation toxicity study in rats. Finally, we consider the regulatory guidelines for the application of NAMs and potential use of different lung models for aerosol toxicity studies depending on the regulatory requirement/context of use.

Role of Lipopolysaccharides in the Inflammation and Pyroptosis of Alveolar Epithelial Cells in Acute Lung Injury and Acute Respiratory Distress Syndrome

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) represent a spectrum of common critical respiratory conditions characterized by damage and death of alveolar epithelial cells (AECs). Pyroptosis is a form of programmed cell death with inflammatory characteristics, and activation of pyroptosis markers has been observed in AECs of patients with ALI/ARDS. Lipopolysaccharides (LPS) possess strong pro-inflammatory effects and are a crucial pathological factor leading to ALI in patients and animals. In LPS-induced ALI models, AECs undergo pyroptosis. However, physiologically and pathologically relevant concentrations of LPS lead to minor effects on AEC cell viability and minimal induction of cytokine release in vitro and do not induce classical pyroptosis. Nevertheless, LPS can enter the cytoplasm directly and induce non-classical pyroptosis in AECs when assisted by extracellular vesicles from bacteria, HMGB1, and pathogens. In this review, we have explored the effects of LPS on AECs concerning inflammation, cell viability, and pyroptosis, analyzing key factors that influence LPS actions. Notably, we highlight the intricate response of AECs to LPS within the framework of ALI and ARDS, emphasizing the variable induction of pyroptosis. Despite the minimal effects of LPS on AEC viability and cytokine release in vitro, LPS can induce non-classical pyroptosis under specific conditions, presenting potential pathways for therapeutic intervention. Collectively, understanding these mechanisms is crucial for the development of targeted treatments that mitigate the inflammatory responses in ALI/ARDS, thereby enhancing patient outcomes in these severe respiratory conditions.

A novel chemically defined medium for the biotechnological and biomedical exploitation of the cell factory Leishmania tarentolae

The development of media for cell culture is a major issue in the biopharmaceutical industry, for the production of therapeutics, immune-modulating molecules and protein antigens. Chemically defined media offer several advantages, as they are free of animal-derived components and guarantee high purity and a consistency in their composition. Microorganisms of the genus Leishmania represent a promising cellular platform for production of recombinant proteins, but their maintenance requires supplements of animal origin, such as hemin and fetal bovine serum. In the present study, three chemically defined media were assayed for culturing Leishmania tarentolae, using both a wild-type strain and a strain engineered to produce a viral antigen. Among the three media, Schneider's Drosophila Medium supplemented with Horseradish Peroxidase proved to be effective for the maintenance of L. tarentolae promastigotes, also allowing the heterologous protein production by the engineered strain. Finally, the engineered strain was maintained in culture up to the 12th week without antibiotic, revealing its capability to produce the recombinant protein in the absence of selective pressure.

Protective role of fetal bovine serum on PLHC-1 spheroids exposed to a mixture of plastic additives: A lipidomic perspective

The use of fetal bovine serum (FBS) in cell culture is being questioned for scientific and ethical reasons, prompting the exploration of alternative approaches. Nevertheless, the influence of FBS on cell functioning, especially in fish cells, has not been comprehensively examined. This study aims to evaluate the impact of FBS on the lipidome of PLHC-1 spheroids and investigate cellular and molecular responses to plastic additives in the presence/absence of FBS. Lipidomic analyses were conducted on PLHC-1 cell spheroids using liquid chromatography coupled with a high-resolution quadrupole time-of-flight mass spectrometer (HRMS-QToF). The removal of FBS from the culture medium for 24 h significantly changed the lipid profile of spheroids, resulting in a depletion of cholesterol esters (CEs), phosphatidylcholines (PCs) and lyso-phosphatidylcholines (LPCs), while ceramides and certain glycerophospholipids slightly increased. Additionally, the exclusion of FBS from the medium led to increased cytotoxicity caused by a mixture of plastic additives and increased lipidomic alterations, including an elevation of ceramides. This study emphasizes the protective role of serum components in fish liver spheroids against a mixture of plastic additives and underscores the importance of considering exposure conditions when studying metabolomic and lipidomic responses to toxicants.

Biochemical and functional characterization of heat-inactivated coelomic fluid from earthworms as a potential alternative for fetal bovine serum in animal cell culture

Fetal bovine serum (FBS) plays a pivotal role in animal cell culture. Due to ethical and scientific issues, searching for an alternative, comprising the three R's (Refinement, Reduction and Replacement) gained global attention. In this context, we have identified the heat inactivated coelomic fluid (HI-CF) of the earthworm, Perionyx excavatus as a potential alternative for FBS. Briefly, we formulated HI-CF (f-HICF) containing serum free medium which can aid the growth, attachment, and proliferation of adherent cells, similar to FBS. In this study, we investigated the biochemical characterization, sterility, stability, formulation, and functional analysis of HI-CF as a supplement in culturing animal cells. Notably, vitamins, micronutrients, proteins, lipids, and trace elements are identified and compared with FBS for effective normalization of the serum free media. HI-CF is tested to be devoid of endotoxin and mycoplasma contamination thus can qualify the cell culture grade. The f-HICF serum free media was prepared, optimised, and tested with A549, HeLa, 3T3, Vero and C2C12 cell lines. Our results conclude that f-HICF is a potential alternative to FBS, in accordance with ethical concern; compliance with 3R's; lack of unintended antibody interactions; presence of macro and micronutrients; simple extraction; cost-effectiveness and availability.

Longitudinal characterization of TK6 cells sequentially adapted to animal product-free, chemically defined culture medium: considerations for genotoxicity studies

Introduction: In vitro approaches are an essential tool in screening for toxicity of new chemicals, products and therapeutics. To increase the reproducibility and human relevance of these in vitro assessments, it is advocated to remove animal-derived products such as foetal bovine serum (FBS) from the cell culture system. Currently, FBS is routinely used as a supplement in cell culture medium, but batch-to-batch variability may introduce inconsistency in inter- and intra-lab assessments. Several chemically defined serum replacements (CDSR) have been developed to provide an alternative to FBS, but not every cell line adapts easily and successfully to CDSR-supplemented medium, and the long-term effect on cell characteristics remains uncertain. Aim: The aim of this study was to adapt the TK6 cell line to animal-product free CDSR-supplemented medium and evaluate the long-term effects on cell health, growth, morphology, phenotype, and function. This included a provisional assessment to determine the suitability of the transitioned cell line for standardised genotoxicity testing using the "in vitro mammalian cell micronucleus test" (OECD TG 487). Materials and methods: Gradual adaptation and direct adaptation methodologies were compared by assessing the cell proliferation, size and viability every passage until the cells were fully adapted to animal-free CDSR. The metabolic activity and membrane integrity was assessed every 4-8 passages by PrestoBlue and CytoTox-ONE™ Homogeneous Membrane Integrity Assay respectively. A detailed morphology study by high content imaging was performed and the expression of cell surface markers (CD19 and CD20) was conducted via flow cytometry to assess the potential for phenotypic drift during longer term culture of TK6 in animal-free conditions. Finally, functionality of cells in the OECD TG 487 assay was evaluated. Results: The baseline characteristics of TK6 cells cultured in FBS-supplemented medium were established and variability among passages was used to set up acceptance criteria for CDSR adapted cells. TK6 were adapted to CDSR supplemented medium either via direct or gradual transition reducing from 10% v/v FBS to 0% v/v FBS. The cell growth rate was compromised in the direct adaptation and therefore the gradual adaptation was preferred to investigate the long-term effects of animal-free CDSR on TK6 cells. The new animal cells showed comparable (p > 0.05) viability and cell size as the parent FBS-supplemented cells, with the exception of growth rate. The new animal free cells showed a lag phase double the length of the original cells. Cell morphology (cellular and nuclear area, sphericity) and phenotype (CD19 and CD20 surface markers) were in line (p > 0.05) with the original cells. The new cells cultured in CDSR-supplemented medium performed satisfactory in a pilot OECD TG 487 assay with compounds not requiring metabolic activation. Conclusion: TK6 cells were successfully transitioned to FBS- and animal product-free medium. The new cell cultures were viable and mimicked the characteristics of FBS-cultured cells. The gradual transition methodology utilised in this study can also be applied to other cell lines of interest. Maintaining cells in CDSR-supplemented medium eliminates variability from FBS, which in turn is likely to increase the reproducibility of in vitro experiments. Furthermore, removal of animal derived products from cell culture techniques is likely to increase the human relevance of in vitro methodologies.

Replacing animal-derived components in in vitro test guidelines OECD 455 and 487

The evaluation of single substances or environmental samples for their genotoxic or estrogenic potential is highly relevant for human- and environment-related risk assessment. To examine the effects on a mechanism-specific level, standardized cell-based in vitro methods are widely applied. However, these methods include animal-derived components like fetal bovine serum (FBS) or rat-derived liver homogenate fractions (S9-mixes), which are a source of variability, reduced assay reproducibility and ethical concerns. In our study, we evaluated the adaptation of the cell-based in vitro OECD test guidelines TG 487 (assessment of genotoxicity) and TG 455 (detection of estrogenic activity) to an animal-component-free methodology. Firstly, the human cell lines A549 (for OECD TG 487), ERα-CALUX® and GeneBLAzer™ ERα-UAS-bla GripTite™ (for OECD TG 455) were investigated for growth in a chemically defined medium without the addition of FBS. Secondly, the biotechnological S9-mix ewoS9R was implemented in comparison to the induced rat liver S9 to simulate in vivo metabolism capacities in both OECD test guidelines. As a model compound, Benzo[a]pyrene was used due to its increased genotoxicity and endocrine activity after metabolization. The metabolization of Benzo[a]Pyrene by S9-mixes was examined via chemical analysis. All cell lines (A549, ERα-CALUX® and GeneBLAzer™ Erα-UAS-bla GripTite™) were successfully cultivated in chemically defined media without FBS. The micronucleus assay could not be conducted in chemically defined medium due to formation of cell clusters. The methods for endocrine activity assessment could be conducted in chemically defined media or reduced FBS content, but with decreased assay sensitivity. The biotechnological ewoS9R showed potential to replace rat liver S9 in the micronucleus in FBS-medium with A549 cells and in the ERα-CALUX® assay in FBS- and chemically defined medium. Our study showed promising steps towards an animal-component free toxicity testing. After further improvements, the new methodology could lead to more reproducible and reliable results for risk assessment.

A Non-Conventional Platinum Drug against a Non-Small Cell Lung Cancer Line

A dinuclear Pt(II) complex with putrescine as bridging polyamine ligand ([Pt₂Put₂(NH₃)₄]Cl₄) was synthesized and assessed as to its potential anticancer activity against a human non-small cell lung cancer line (A549), as well as towards non-cancer cells (BEAS-2B). This effect was evaluated through in vitro cytotoxicity assays (MTT and SRB) coupled to microFTIR and microRaman spectroscopies, the former delivering information on growth-inhibiting and cytotoxic abilities while the latter provided very specific information on the metabolic impact of the metal agent (at the sub-cellular level). Regarding cancer cells, a major impact of [Pt₂Put₂(NH₃)₄]Cl₄ was evidenced on cellular proteins and lipids, as compared to DNA, particularly via the Amide I and Amide II signals. The effect of the chelate on non-malignant cells was lower than on malignant ones, evidencing a promising low toxicity towards healthy cells.

Culturing Human Lung Adenocarcinoma Cells in a Serum-Free Environment

The human lung adenocarcinoma cell line A549 is commonly used in cancer research as a model of malignant alveolar type II epithelial cells. A549 cells are frequently cultured in Ham's F12K (Kaighn's) or Dulbecco's Modified Eagle's Medium (DMEM), supplemented with glutamine and 10% fetal bovine serum (FBS). However, the use of FBS presents significant scientific concerns, such as the presence of undefined components and batch-to-batch variation leading to possible reproducibility issues in experiments and readouts. This chapter describes how to transition A549 cells to FBS-free medium and gives some insights on the further characterizations and functionality assays that would be necessary to perform for the validation of the cultured cells.