3-D printing of human tissue

A team led by University of California, San Francisco (UCSF) has developed a technique to build tiny models of human tissues, called organoids, more precisely than ever before, using a process that turns human cells into a biological equivalent of LEGO bricks. These mini-tissues in a dish can be used to study how particular structural features of tissue affect normal growth or go awry in cancer. They could be used for therapeutic drug screening and to help teach researchers how to grow whole human organs.
The new technique -- called DNA Programmed Assembly of Cells (DPAC) and reported in the journal Nature Methods, allows researchers to create arrays of thousands of custom-designed organoids, such as models of human mammary glands containing several hundred cells each, which can be built in a matter of hours.
There are few limits to the tissues this technology can mimic, said Zev Gartner, PhD, the paper's senior author and an associate professor of pharmaceutical chemistry at UCSF. "We can take any cell type we want and program just where it goes. We can precisely control who's talking to whom and who's touching whom at the earliest stages. The cells then follow these initially programmed spatial cues to interact, move around, and develop into tissues over time."
"One potential application," Gartner said, "would be that within the next couple of years, we could be taking samples of different components of a cancer patient's mammary gland and building a model of their tissue to use as a personalised drug screening platform. Another is to use the rules of tissue growth we learn with these models to one day grow complete organs."
Studying how the cells of complex tissues like the mammary gland self-organize, make decisions as groups, and break down in disease has been a challenge to researchers. The living organism is often too complex to identify the specific causes of a particular cellular behavior. On the other hand, cells in a dish lack the critical element of realistic 3-D structure.
"This technique lets us produce simple components of tissue in a dish that we can easily study and manipulate," said Michael Todhunter, PhD, who led the new study with Noel Jee, PhD, when both were graduate students in the Gartner research group. "It lets us ask questions about complex human tissues without needing to do experiments on humans."
Gartener’s group hopes to use what they learn from simple models of different tissue types to ultimately build functional human tissues like lung and kidney and neural circuits using larger-scale techniques.
"Building functional models of the complex cellular networks such as those found in the brain is probably one of the highest challenges you could aspire to," Todhunter said. "DPAC now makes a lofty goal like that seem achievable."
Reference: University of California, San Francisco (UCSF). "DNA-guided 3-D printing of human tissue is unveiled." ScienceDaily. ScienceDaily, 31 August 2015.