Artificially printed tissue may one day revolutionize how diseased organs are treated, fractured bones are fixed, and drugs are tested without human subjects. A great deal of progress has already been made toward this goal, but a major hurdle, that of integrating vasculature and bringing together different cell types into a functional whole, has significantly limited that progress. Now researchers at Harvard University report in journal Advanced Materials on a new method of 3D printing constructs made of three different cell types, including ones that line blood vessel walls.
Because any substantially large chunk of tissue requires oxygen to penetrate into its interior, the vessels within the construct allow for much larger pieces of printed tissue to be created.
Some details from a Harvard news release:
To print 3D tissue constructs with a predefined pattern, the researchers needed functional inks with useful biological properties, so they developed several “bio-inks”—tissue-friendly inks containing key ingredients of living tissues. One ink contained extracellular matrix, the biological material that knits cells into tissues. A second ink contained both extracellular matrix and living cells.
To create blood vessels, they developed a third ink with an unusual property: it melts as it cools, rather than as it warms. This allowed the scientists to first print an interconnected network of filaments, then melt them by chilling the material and suction the liquid out to create a network of hollow tubes, or vessels.
The Harvard team then road-tested the method to assess its power and versatility. They printed 3D tissue constructs with a variety of architectures, culminating in an intricately patterned construct containing blood vessels and three different types of cells—a structure approaching the complexity of solid tissues.
Moreover, when they injected human endothelial cells into the vascular network, those cells regrew the blood-vessel lining.
Article in Advanced Materials: 3D Bioprinting of Vascularized, Heterogeneous Cell-Laden Tissue Constructs…