If you send stem cells just the right signals, they’ll develop into any one of a wide range of tissues, from retina to spinal cord to heart muscle. But which signals to send? A team at John Hopkins has painstakingly gone over more than 30 techniques for getting cells to differentiate and consolidated them into a simple procedure that has successfully been used to turn at least 11 lines of stem cells into healthy, beating heart cells---all without introducing the cancer-causing mutations that can plague this kind of work. "We took the recipe for this process from a complex minestrone to a simple miso soup," says study leaderElias Zambidis. What’s the Context:
It’s not unusual for each lab in certain field to have its own recipe for common processes, assembled by trial and error and cemented by tradition---kind of like your mother’s meatloaf. The Hopkins group examined hundreds of combinations of 48 different variables, ranging from timing, buffers, temperature, and even the size of the dishes labs grew cells in.
Traditionally, scientists use viruses to introduce into blood cells the genes needed to transform them into induced pluripotent stem cells, which can then be coaxed into becoming heart muscle. There's just one problem: the viruses can introduce dangerous mutations.
The new research uses plasmids (small loops of free-floating DNA) instead; the team discovered that briefly shocking the cells can get them to admit plasmids in through their membranes and that the plasmids last long enough to make cells undergo the transition.
Stem cells are being used to grow all kinds of tissues for potential transplant: researchers recently grew a retina from stem cells, and in the 2010 the US approved the first trial of spinal cord stem cell transplants.
Reference: Burridge, et al. A universal system for highly efficient cardiac differentiation of human induced pluripotent stem cells that eliminates interline variability. PLoS ONE, 6 (4): e18293 doi:10.1371/journal.pone.0018293Video credit: Johns Hopkins