Page 254 - IJB-10-3

International Journal of Bioprinting Bioprinting organoids for toxicity testing

1. Introduction the three cell lines in the extruded hydrogel were not able
to assemble into a liver Disse space-like microstructure.
Human health is threatened by various pollutants in the Organoids are considered a strategy of biomimetic tissue
living environment. Small-sized (<5 mm in diameter) microstructures. Human-induced pluripotent stem cells
plastics, known as microplastics (MPs), have been widely (hiPSCs), reprogramed from adult somatic cells, can
detected in the environment, including marine, drinking differentiate into multitype of cells with the intrinsic
water, air, and food. Polyethylene, polypropylene, ability to self-assemble into organoids in vitro. This avoids
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polystyrene, and polyvinyl chloride MPs are predominant ethical issues associated with using human stem cells and
in aquatic environments. Recently, MPs have been found primary human cells, providing multiple cell sources for
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in human blood, the placenta, and the liver tissue of establishing in vitro human artificial organs. Moreover,
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liver cirrhosis patients, raising increasing global concerns hiPSCs carry individual genetic information, and
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about its potential effects on human health. Danopoulos 3D-bioprinted hiPSC can provide a personalized genetic
et al. systematically reviewed the scientific data from background for toxicological studies. Nonetheless, the
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studies regarding MP effects on human cells and attempted efficient production of hiPSC-derived liver Disse space
to establish thresholds of MP toxicity in human risk organoids (DOs) suitable for complex environmental
assessment. However, they pointed out that the overall toxicology assessment remains challenging.
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certainty of collected evidence was graded as low. Large-
scaled biomimetic human tissue models with physiological Here, we mass-produced multicellular DOs based on
relevance for evaluating MP toxicity are missing. healthy donor and patient-derived hiPSCs using electro-
assisted inkjet bioprinting. The chemically defined
The substantial surface area and hydrophobic alginate/laminin bioink and 3D microenvironment
nature of MPs make them ideal vectors for transporting of microspheres facilitated multicellular crosstalk and
environmental xenobiotics. Tetrabromobisphenol A mutually enhanced the maturation of hiPSC-derived
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(TBBPA), an emerging environmental xenobiotic, is one progenitor cells, thus generating DOs mimicking Disse
of the most widely used brominated flame retardants. space features. PS-MPs (1 μm) crossed the barrier of
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It can reach relatively high concentrations (850–4870 the hydrogel matrix and were preferentially taken up by
ng/L) in rivers and has been frequently detected in endothelial cells followed by dispersing throughout the
aquatic food. TBBPA has been detected in breast milk whole organoids. Additionally, co-exposure to MPs and
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and umbilical cord blood of human owing to continuous TBBPA enhanced the accumulation of pollutants within
exposure. Studies have demonstrated that TBBPA disrupts DOs at the tested time points. The alcoholic liver disease
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thyroid homeostasis and liver metabolism. Due to their (ALD) patient-derived hiPSCs efficiently formed DOs with
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high propensity to accumulate in environmental media, specific disease transcriptional profiles. Transcriptional
both MPs and TBBPA can co-exist in the same system. and biochemical evaluations showed that co-exposure
Xu et al. found that TBBPA could be adsorbed onto the to MPs and TBBPA severely impacted patient-derived
surface of polystyrene MPs (PS-MPs), inhibiting its DOs over healthy donor organoids, suggesting that both
biotransformation. This process may lead to unexpected hereditary factors and pollutants could strengthen the
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and complex toxic effects. A recent study has found that susceptibility of organisms to environmental toxicants
compared with single exposure, co-exposure to MPs (Figure 1A). This study provided the proof of concept that
and TBBPA resulted in a more severe disruption of the hiPSC-derived in vitro models fabricated by bioprinting
hepatic redox status of zebrafish, increasing the risk of liver technologies offer a potential platform for investigating
fibrosis and cirrhosis. However, due to species differences personalized toxicology.
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between zebrafish and human liver, there is a need for
models capable of accurately simulating human liver 2. Materials and methods
toxicity responses to conduct further research on the toxic
effects and mechanisms of MPs and TBBPA co-exposure. 2.1. Cell culture
hiPSCs-N, reprogrammed from the peripheral blood
Human liver Disse space composed of hepatocytes, cells of a healthy male, were purchased from Nuwacell
endothelial cells, and hepatic stellate cells (HSCs) plays a Biotechnologies Co., Ltd. (RC01001-A). hiPSCs-
crucial regulatory role in the pathogenesis of liver fibrosis AC19 were reprogrammed from the peripheral blood
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and cirrhosis. A recent study has demonstrated that a three- mononuclear cells of a 64-year-old male patient with ALD.
dimensional (3D)-bioprinted in vitro model composed of The patient provided written consent, and ethical approval
the three types of cells could recapitulate the critical features was obtained from the Institution Review Board of
involved in fibrogenesis. Due to compatibility limitations Tsinghua University. The reprogramming of hiPSCs-AC19
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between cell assembly and extrusion printing techniques, was performed with Sendai virus-based reprogramming

Volume 10 Issue 3 (2024) 246 doi: 10.36922/ijb.1403