Bioprinting enthusiasts envision a future where we’ll be able to print functional human organs on demand, putting an end to transplant waiting lists and health problems and deaths related to organ failure.
That future isn’t unrealistic nor out of reach, but it’s going to arrive slowly—artificially re-creating an organ is a massively complicated task involving dozens of small pieces that must fit together perfectly in order to work as intended.
One of those pieces fell into place just last week, when a multi-national team published a study in the journal Biomicrofluidics detailing its efforts to develop 3D printed vascularized liver tissue. They used the artificial tissue for drug toxicity testing, mimicking a living environment to analyze the effect certain drugs would have on patients.
The team printed blood vessels for the liver tissue using a gel-based “sacrificial” ink, so named because the ink is temporary—it’s used to create the hollow channels that become vessels, but washed away once the vessels are set.
They then added endothelial stem cells to the vessels (endothelial cells line the inside of all blood vessels, forming a selectively permeable barrier across which chemicals and white blood cells can move).
Adding endothelial cells to the bioprinted vessels had the effect of delaying permeability of biomolecules into the 3D liver construct, and increasing viability of the tissue’s other cells. In short, the endothelial layer played a protective role, just like it does in our living blood vessels.
“Based on our finding, the endothelial layer delays the drug diffusion response, compared to without the endothelial layer,”said Su Ryon Shin, an instructor conducting research at the Harvard Medical School and one of the study’s authors. “They don’t change any drug diffusion constants, but they delay the permeability, so they delay the [response] as it takes time to pass through the endothelial layer.”
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