Muscle and Bone, Fresh from the Printer
BY LAUREN UZDIENSKI, JANUARY 16, 2007
MIT's Technology Review reported recently on a new development out of Carnegie Mellon and the University of Pittsburgh: a custom ink-jet printer that can print tissue using stem cells from mice and growth factor.
This is how the Carnegie Mellon/University of Pittsburgh system works: the printer is loaded with a dilute solution containing the growth factor BMP-2, which turns stem cells into bone cells. A slide is coated with a fibrin matrix, which naturally binds growth factors. One drop at a time, the growth factor ink is then printed onto the slide in separate square patterns. The concentration of growth factor on each square varies depending on how much growth factor was printed onto each square. This creates a scaffold onto which stem cells can interact and differentiate into bone and muscle cells.
When the slide was dry, the team coated it with stem cells from mice leg muscles. In the patches of growth factor, the stem cells began to differentiate into bone cells; stem cells that landed on blank spots formed muscle cells, the default pathway for these cells.
This isn't the first time that tissue has been grown in a lab, but what is unique is that the varying concentrations of growth factor enable different types of cells to grow alongside one other. Phil Campbell, who led the team at CMU, comments, "You can envision a scaffold structure where one end promotes bone, one end tendon, the other end muscle." Theoretically, this combination of stem cells and growth factor could be used not only in a culture dish, but actually implanted in damaged tissue.
Of course, this technology is in a nascent state, and humans won't be receiving inkjet knees just yet. Complex growth patterns are still being uncovered and understood. As one of Campbell's colleagues at Carnegie Mellon points out, "One of the biggest limiting factors is [knowing] what to print."
