Organotypic liver culture models: Meeting current challenges in toxicity testing

Abstract

Prediction of chemical-induced hepatotoxicity in humans from in vitro data continues to be a significant challenge for the pharmaceutical and chemical industries. Generally, conventional in vitro hepatic model systems (i.e. 2-D static monocultures of primary or immortalized hepatocytes) are limited by their inability to maintain histotypic and phenotypic characteristics over time in culture, including stable expression of clearance and bioactivation pathways, as well as complex adaptive responses to chemical exposure. These systems are less than ideal for longer-term toxicity evaluations and elucidation of key cellular and molecular events involved in primary and secondary adaptation to chemical exposure, or for identification of important mediators of inflammation, proliferation and apoptosis. Progress in implementing a more effective strategy for in vitro-in vivo extrapolation and human risk assessment depends on significant advances in tissue culture technology and increasing their level of biological complexity. This article describes the current and ongoing need for more relevant, organotypic in vitro surrogate systems of human liver and recent efforts to recreate the multicellular architecture and hemodynamic properties of the liver using novel culture platforms. As these systems become more widely used for chemical and drug toxicity testing, there will be a corresponding need to establish standardized testing conditions, endpoint analyses and acceptance criteria. In the future, a balanced approach between sample throughput and biological relevance should provide better in vitro tools that are complementary with animal testing and assist in conducting more predictive human risk assessment.

Editor’s Highlight: Modeling Compound-Induced FibrogenesisIn VitroUsing Three-Dimensional Bioprinted Human Liver Tissues

“…Cell culture has been used as a surrogate to dissect the mechanistic details underlying HC dysfunction and fibrogenic outcome; however, conventional two-dimensional (2D), cell-based hepatic model systems do not reliably recapitulate liver structure, function, and its inherent multicellular architecture (LeCluyse et al, 2012). This is largely due to the absence of non-parenchymal cells (NPCs) relevant to liver injury and fibrogenic response.…”

Characterization of a Rat Multi-Cell Type 3D-Liver Microtissue System

“…Current in vitro hepatic model systems often fail to predict hepatic injury because of the rapid loss of expression of phase I and II biotransformation enzymes and efflux pumps during cultivation [42]. Hepatocytes cultured as monolayers rapidly lose the expression and functional activities of key cytochrome P450 enzymes, multi-drug resistance proteins, proteins required for albumin and transferring, and glucocorticoid regeneration within the first 24-48 h [43][44][45].…”

Human skin-derived stem cells as a novel cell source for in vitro hepatotoxicity screening of pharmaceuticals

“…Current human cell models are scarce or not fully adequate for toxicity screening of pharmaceuticals and other chemical compounds [16,45]. Therefore, novel cell models need to be explored.…”

“…These cell lines are readily available and can be kept in culture for long periods of time, but they suffer from genotypical instability and decreased or even absent metabolic capacity. In addition, currently available cell lines do not represent population diversity [16]. Stem cells could form a novel and attractive alternative human cell source to develop in vitro systems for predicting liver toxicity.…”