Page 109 - v11i4

International Journal of Bioprinting 3D bioprinting for translational toxicology

revealed the carcinogenic mechanisms of polycyclic simulations, offering additional options and potential
aromatic hydrocarbons, marking the advent of modern avenues for reducing animal testing. Future research
toxicological studies. In the early 19th century, French should continue to explore the application potential of
24
scientist Mathieu Orfila systematically validated the these novel methods to facilitate sustainable progress in
effects of toxins through animal experimentation, whereas toxicological research.
Magendie and Claude Bernard explored neurotoxic
mechanisms. 25–28 These pioneering studies laid the 2.3. Disruption in in vitro models: From cell cultures
foundation for the experimental methodologies that to organ simulation
underpin modern toxicology. Over an extended period, toxicological research principally
depended on whole-animal experimentation and human
2.2. The era of animal model dominance observational studies. However, challenges in accurately
The application of animal models in toxicological research replicating complex exposure scenarios, coupled with
has undergone a significant evolution, evolving from interspecies and individual variability between humans
preliminary investigations to routine applications. In and various animal models, have impeded a holistic
1927, J.W. Trevan, drawing upon Paracelsus’s foundational understanding of the toxicological effects of exogenous
principles, introduced the concept of the median lethal substances, complicating the research processes. Recent
dose (LD ). By employing statistical methodologies, advancements in tissue engineering and molecular biology
50
Trevan defined LD as a universal benchmark for have facilitated the development of highly refined in vitro
50
evaluating acute toxicity, laying the groundwork for future models that emulate human tissue functionality. These
advancements in toxicity testing. 29,30 This innovation include widely utilized 2D and 3D cell culture systems,
marked a pivotal shift from qualitative to quantitative organoids, and microfluidic chips. Such innovations are
toxicological analysis, providing a scientific basis for progressively diminishing dependence on conventional
subsequent evaluations. By the mid-20th century, animal animal-based approaches in toxicological research.
experimentation was established as the cornerstone of
toxicological investigations. The LD test was extensively 2.3.1. Two-dimensional monolayer culture
31
50
utilized for categorizing the acute toxicity profiles of Two-dimensional cell cultures represent a classical in vitro
industrial compounds and pharmaceutical agents, serving model extensively employed in toxicological investigations.
as a vital tool for assessing chemical toxicity. 32,33 Originating from primary cell lines, cancer-derived
cell lines, and stem cells, these systems have become
Through animal experiments, researchers obtained indispensable tools in biological research since Harrison’s
foundational knowledge regarding the ADME of drugs, groundbreaking achievement in animal cell culture in
as well as their potential toxicities and adverse effects. 1901. The discovery of HeLa cells in 1951 initiated the
34
37
During this era, animal testing not only played a critical extensive utilization of cancer cell lines as readily accessible
role in drug development but also supported the toxicity experimental platforms. Subsequent milestones included
38
assessment of environmental pollutants. However, the successful isolation and establishment of mouse
growing ethical concerns surrounding the extensive and human embryonic stem cell lines in 1981 and 1998,
use of animal testing, particularly the ethical dilemmas respectively. 39,40 Beyond cellular models, Bruce Ames’
associated with animal suffering, began to emerge. In 1959, development of the bacterial reverse mutation assay
the introduction of the 3R principle initiated a paradigm in 1975, incorporating a liver microsomal metabolic
shift in ethical considerations for animal testing. This activation system, enabled efficient high-throughput
31
principle advocated for minimizing animal usage through screening for carcinogenic substances, thereby reducing
alternative methods and refining experimental procedures dependence on mammalian experimental systems. 41,42 In
to alleviate animal suffering, steering toxicological research 2007, Zeiger achieved a groundbreaking milestone by
42
toward exploring efficient in vitro models and alternative reprogramming human somatic cells to generate the first
approaches to reduce reliance on animal testing. 10 induced pluripotent stem cell (iPSC) lines.
Despite these ethical considerations, animal models Today, widely adopted 2D cell systems encompass
remained integral to toxicological studies for decades. human colorectal adenocarcinoma (Caco-2), Madin–
35
They enabled researchers to simulate complex biological Darby canine kidney (MDCK), human alveolar basal
processes and evaluate the toxic effects of substances in vivo, epithelial (A549), and bronchial epithelial (BEAS-2B) cell
providing indispensable support for drug development lines, which serve diverse applications in assessing the
and environmental safety assessments. Nevertheless, toxicity of chemicals, pharmaceuticals, and environmental
36
advancements in science and technology have spurred pollutants. For instance, Caco-2 cells are extensively
the emergence of in vitro models and computational utilized to investigate intestinal absorption and drug

Volume 11 Issue 4 (2025) 101 doi: 10.36922/IJB025210209