Shaochen Chen, NanoEngineering professor at the UC San Diego Jacobs School of Engineering, said: "We've made a tool that pharmaceutical companies could use to do pilot studies on their new drugs, and they won't have to wait until animal or human trials to test a drug's safety and efficacy on patients. This would let them focus on the most promising drug candidates earlier on in the process."
The liver plays a critical role in how the body metabolises drugs and produces key proteins. This is why liver models are increasingly being developed in labs as platforms for drug screening. However, it is said that existing models so far lack both the complex micro-architecture and diverse cell makeup of a real liver.
The UC San Diego team engineered a human liver tissue model that more closely resembles the real thing - a diverse combination of liver cells and supporting cells systematically organised in a hexagonal pattern.
To do this, the team developed a novel bioprinting technology which it says can rapidly produce complex 3D microstructures that mimic the sophisticated features found in biological tissues. The liver tissue was printed in two steps. First, the team printed a honeycomb pattern of 900-micrometer-sized hexagons, each containing liver cells derived from human stem cells. Next, endothelial and mesenchymal supporting cells were printed in the spaces between the stem-cell-containing hexagons.
The entire structure measures 3 × 3cm2, is 200µm thick and is claimed to take seconds to print rather than hours.
The researchers then tested the tissue's ability to perform liver functions, such as albumin secretion and urea production, and compared it to other models. They found that their model was able to maintain these functions over a longer time period than other liver models.
"The liver tissue constructed by this novel 3D printing technology will also be extremely useful in reproducing in vitro disease models such as hepatitis, cirrhosis, and cancer,” said Professor Shu Chien, director of the Institute of Engineering in Medicine at UC San Diego. “Such realistic models will be invaluable for the study of the pathophysiology and metabolic abnormalities in these diseases and the efficacy of drug therapies."