The Wyss Institute for Biologically Inspired Engineering at the Harvard School of Engineering and Applied Sciences has created a 3D printer that can lay down four different types of cells at the same time. The breakthrough in that research has been the ability to create blood vessels that can feed living tissue.
"You can simultaneously print cells, vasculature as well as extra-cellular matrix. Each one of those are extremely important components within human tissue," said David Kolesky, a graduate student at the Wyss Institute.
"You can also print cells on top of and around it. As you can imagine, human tissue is inherently complex and composite and you have multiple cell types right next to each other - on top of and around vasculature. In fact every cell is within a few microns of a blood vessel in your body."
3D printing also allows enough tissue and supportive vasculature to be constructed quickly so that enough living cells can survive to create functional tissue.
Organovo said it has also overcome the vascular issue to a degree. "We have achieved thicknesses of greater than 500 microns, and have maintained liver tissue in a fully functional state with native phenotypic behavior for at least 40 days," said Michael Renard, Organovo's executive vice president of commercial operations.
How it works
The University of Toronto's PrintAlive Bioprinter 3D skin printer works by placing the patient's cells along with other biomaterials into a micro-device, which then pushes them out through several channels. The biomaterials are then mixed, causing a chemical reaction that forms a "mosaic hydrogel", a sheet-like substance compatible with the growth of cells into living tissues. The hydrogel allows the various dermis cells to be seeded in precise and controlled patterns.
The printing technique is different from others, the scientists said, because it doesn't require an artificial, but biodegradable, scaffolding to hold the cells together. Typically, 3D bio printing requires cells to be placed onto an artificial structure capable of supporting three-dimensional tissue formation.
The placement of the cells by the printer is so precise that the researchers were able to spell words, such as Toronto, demonstrating how they could mimic the natural placement of cells in living tissues.
The mosaic hydrogel sheets are collected around a drum, which allows the formation of layers as it turns, creating, in essence, three-dimensional, functional tissues.
"In this case, when we put the cells in the right places, we create cellular organization quite naturally," Leng said.
So what's the next step?
Along with treating burn victims, the 3D-printed tissue could be used for testing therapeutic drugs, potentially eliminating the need for arduous and highly regulated animal and human trials.
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