A new animal product free defined medium for 2D and 3D culturing of normal and cancer cells to study cell proliferation and migration as well as dose response to chemical treatment

High-throughput non-homogenous 3D polycaprolactone scaffold for cancer cell and cancer-associated fibroblast mini-tumors to evaluate drug treatment response

High-throughput screening (HTS) three-dimensional (3D) tumor models are a promising approach for cancer drug discovery, as they more accurately replicate in vivo cell behavior than two-dimensional (2D) models. However, assessing and comparing current 3D models for drug efficacy remains essential, given the significant influence of cellular conditions on treatment response. To develop in vivo mimicking 3D models, we evaluated two HTS 3D models established in 96-well plates with 3D polycaprolactone (PCL) scaffolds fabricated using two distinct methods, resulting in scaffolds with either homogenous or non-homogenous fiber networks. These models, based on human HeLa cervical cancer cells and cancer-associated fibroblasts (CAFs) cultured as mono- or co-cultures within the 3D scaffolds, revealed that anticancer drug paclitaxel (PTX) exhibited consistently higher inhibitory concentration 50 (IC50) in 3D (≥ 1000 nM) compared to 2D (≥ 100 nM), indicating reduced toxicity on cells cultured in 3D. Interestingly, the toxicity of PTX was significantly lower on mini-tumors in non-homogenous 3D (IC50: 600 or 1000 nM) than in homogenous 3D cultures (IC50 exceeding 1000 nM). Microscopic studies revealed that the non-homogenous scaffolds closely resemble the tumor collagen network than their homogeneous counterpart. Both 3D scaffolds offer optimal pore size, facilitating efficient cell infiltration into the depth of 58.1 ± 1.2 µm (homogenous) and 86.4 ± 9.8 µm (non-homogenous) within 3D cultures. Cells cultured in the 3D non-homogenous systems exhibited drug treatment responses closer to in vivo conditions, highlighting the role of scaffold structure and design on cellular response to drug treatment. The PCL-based 3D models provide a robust, tunable, and efficient approach for the HTS of anti-cancer drugs compared to conventional 2D systems.

Advancing humanized 3D tumor modeling using an open access xeno-free medium

Despite limitations like poor mimicry of the human cell microenvironment, contamination risks, and batch-to-batch variation, cell culture media with animal-derived components such as fetal bovine serum (FBS) have been used in vitro for decades. Moreover, a few reports have used animal-product-free media in advanced high throughput three-dimensional (3D) models that closely mimic in vivo conditions. To address these challenges, we combined a high throughput 3D model with an open access, FBS-free chemically-defined medium, Oredsson Universal Replacement (OUR) medium, to create a more realistic 3D in vitro drug screening system. To reach this goal, we report the gradual adaptation procedure of three cell lines: human HeLa cervical cancer cells, human MCF-7 breast cancer cells, and cancer-associated fibroblasts (CAFs) from FBS-supplemented medium to OUR medium, while closely monitoring cell attachment, proliferation, and morphology. Our data based on cell morphology studies with phase contrast and real-time live imaging demonstrates a successful adaptation of cells to proliferate in OUR medium showing sustained growth kinetics and maintaining population doubling time. The morphological analysis demonstrates that HeLa and MCF-7 cells displayed altered cell morphology, with a more spread-out cytoplasm and significantly lower circularity index, while CAFs remained unaffected when grown in OUR medium. 3D fiber scaffolds facilitated efficient cell distribution and ingrowth when grown in OUR medium, where cells expand and infiltrate into the depths of 3D scaffolds. Drug toxicity evaluation of the widely used anti-cancer drug paclitaxel (PTX) revealed that cells grown in 3D cultures with OUR medium showed significantly lower sensitivity to PTX, which was consistent with the FBS-supplemented medium. We believe this study opens the way and encourages the scientific community to use animal product-free cell culture medium formulations for research and toxicity testing.

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.

Increasing sustainability and reproducibility of in vitro toxicology applications: serum-free cultivation of HepG2 cells

Fetal Bovine Serum (FBS) is an important ingredient in cell culture media and the current standard for most cells in vitro. However, the use of FBS is controversial for several reasons, including ethical concerns, political, and societal pressure, as well as scientific problems due to the undefined and variable nature of FBS. Nevertheless, scientists hesitate to change the paradigm without solid data de-risking the switch of their assays to alternatives. In this study, HepG2 cells, a human hepatoblastoma cell line commonly used to study drug hepatotoxicity, were adapted to serum-free conditions by using different commercially available media and FBS replacements. After transition to these new culture conditions, the success of adaptation was determined based on cell morphology and growth characteristics. Long-term culturing capacity for each medium was defined as the number of passages HepG2 cells could be cultured without any alterations in morphology or growth behavior. Two media (Advanced DMEM/F12 from ThermoFisher and TCM® Serum Replacement from MP Biomedicals) showed a long-term cultivation capacity comparable to media containing FBS and were selected for further analysis. Both media can be characterized as serum-free, however still contain animal-derived components: bovine serum albumin (both media) and bovine transferrin (only TCM® serum replacement). To assess the functionality of the cells cultivated in either of the two media, HepG2 cells were treated with reference compounds, specifically selected for their known hepatotoxicity characteristics in man. Different toxicological assays focusing on viability, mitochondrial toxicity, oxidative stress, and intracellular drug response were performed. Throughout the different assays, response to reference compounds was comparable, with a slightly higher sensitivity of serum-free cultivated HepG2 cells when assessing viability/cell death and a lower sensitivity towards oxidative stress. Taken together, the two selected media were shown to support growth, morphology, and function of serum-free cultivated HepG2 cells in the early preclinical safety space. Therefore, these results can serve as a starting point to further optimize culture conditions with the goal to remove any remaining animal-derived components.

Use of serum-free media for peripheral blood mononuclear cell culture and the impact on T and B cell readouts

Introduction

As part of a wider programme of work developing next-generation risk assessment approaches (NGRA) using non-animal methods (NAMs) for safety assessment of materials, Unilever SEAC is exploring the use of a peripheral blood mononuclear cell (PBMC) system to investigate how cells from different arms of the human immune system are impacted by different treatments. To maximise human relevance, the cell cultures are supported by human serum, but this came with some challenges, including an inability to measure induced levels of immunoglobulins due to high background levels. Therefore, a study comparing use of human sera containing media with three different chemically defined serum-free media was undertaken.

Materials and Methods

PBMC were isolated from healthy donors and cultured in the absence (media alone) or presence of stimulation reagents (CpG-ODN plus IL-15, Pokeweed Mitogen (PWM) or Cytostim (CS)), in RPMI plus human serum, AIM-V, CTS OpTmizer T cell expansion SFM or X-VIVO 15 media. T cell (CD4+ and CD8+) and B cell proliferation and viability were measured after 6 days, along with levels of total IgG in the cell culture supernatants.

Results

Each of the serum-free media tested supported good levels of viable and proliferating T cells and B cells over the 6 days of culture, with only a few, small differences across the media, when there was no stimulation. They also enabled detection of a stimulation-evoked increase in IgG levels. There were however some differences in the viability and proliferation responses of T and B cells, to different stimuli, across the different media.

Discussion

The serum-free media formulations tested in this study offer defined systems for. measuring B cell IgG responses, in vitro, in either a 'T cell-independent' (CpG + IL-15) or "T cell-dependent" (PWM or CS) manner and for assessing B cell proliferation, particularly in response to a "T cell-independent" stimulus. However, there are some characteristics and features endowed by human serum that appear to be missing. Therefore, further work is required to optimise animal-free, chemically defined culture conditions for PBMC based assays for inclusion in tiered safety assessments.

Preparation of a universally usable, animal product free, defined medium for 2D and 3D culturing of normal and cancer cells

Since 1958, cell culture media supplemented with fetal bovine serum is used, despite the well-known concerns about animal welfare, reproducibility, reliability, relevance, and safety. To obliterate these concerns and increase scientific accuracy, we recently published an open access, publicly available paper on a defined medium composition to make it possible for any lab to prepare this medium. The medium supports routine culturing and cell banking as well as investigations of growth curves, dose response testing of compounds of cells in 2D and 3D, and cell migration; all important aspects for research and toxicology. Here we give a detailed description of how to mix the defined universal cell culture medium in 14 simple steps to support any entity that wishes to make it. We also list different normal and cancer cell lines that have been cultured in the defined medium.•Open source composition of animal product free universal cell culture medium•Protocols for mixing solutions of small xeno free molecules for supplementation•Protocols for mixing solutions of human proteins for supplementation.

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.

Xeno-Free 3D Bioprinted Liver Model for Hepatotoxicity Assessment

Three-dimensional (3D) bioprinting is one of the most promising methodologies that are currently in development for the replacement of animal experiments. Bioprinting and most alternative technologies rely on animal-derived materials, which compromises the intent of animal welfare and results in the generation of chimeric systems of limited value. The current study therefore presents the first bioprinted liver model that is entirely void of animal-derived constituents. Initially, HuH-7 cells underwent adaptation to a chemically defined medium (CDM). The adapted cells exhibited high survival rates (85-92%) after cryopreservation in chemically defined freezing media, comparable to those preserved in standard medium (86-92%). Xeno-free bioink for 3D bioprinting yielded liver models with high relative cell viability (97-101%), akin to a Matrigel-based liver model (83-102%) after 15 days of culture. The established xeno-free model was used for toxicity testing of a marine biotoxin, okadaic acid (OA). In 2D culture, OA toxicity was virtually identical for cells cultured under standard conditions and in CDM. In the xeno-free bioprinted liver model, 3-fold higher concentrations of OA than in the respective monolayer culture were needed to induce cytotoxicity. In conclusion, this study describes for the first time the development of a xeno-free 3D bioprinted liver model and its applicability for research purposes.