The Center for Alternatives to Animal Testing is an academic center affiliated with the Division of Toxicological Sciences in the Department of Environmental Health Sciences of the Johns Hopkins University Bloomberg School of Public Health.

 

Johns Hopkins School of Public Health

Research Grants 1999-2000

A Bioartificial Liver Lobule for "Toxicity Testing"

Jeffrey M. Macdonald, PhD
University of North Carolina, Chapel Hill, North Carolina

We are tissue engineering liver using the body's natural tissue-replacing cells, progenitors, for toxicity testing. Tissue engineering is a new field combining cell biology and engineering. The liver is the organ primarily responsible for metabolizing toxicants and is the main port of entry for toxicants and especially drugs. We combine concepts in stem cell biology and cell signal pathways (hormones, paracrine, and autocrine factors), with a bioengineering analytical tool [magnetic resonance spectroscopy (MRS)] and a bioengineered device (a hollow-fiber bioreactor). Just x-rays used in computer tomography (CT), MRI and MRS are non-ionizing and do not cause DNA mutations.

We isolate progenitors and culture them in a coaxial hollow-fiber bioreactor perfused with media and extracellular matrix containing the molecules that elicit signal pathways common to progenitors in vivo. A coaxial hollow-fiber bioreactor is simply two synthetic semi-permeable hollow tubes, a smaller tube inserted into a larger tube. The cells grow between the two fibers and media flows in compartments that 'sandwich' the cells. The coaxial fibers mimic the very small physiological unit of the liver, the liver lobule. Therefore, we call this a bioartificial liver lobule. We feed the liver glucose and glycine labeled with stable 13C rather than radioactive 14C. These stable-labeled nutrients and their metabolites are monitored, and the effect of a toxicant on primary metabolism is determined by taking biochemical pictures using MRS at continuous timepoints during toxicant exposure.

The goal of this project is to establish the bioartificial liver lobule for toxicity testing by determining the effect of an environmental toxicant, dibromoethane (a carcinogenic fumigant), on the biological system (i.e., toxicodynamics). The in vivo toxicodynamics will be correlated to secreted stable-labeled nutrient metabolites so that a rapid, high-throughput toxicodynamic MRS toxicity testing assay can be developed.