Stem cells levitated with sound can spontaneously form spherical blobs. The technique could be used to grow tissues or simple miniature organs without researchers having to physically manipulate cells and potentially disrupt them in the process.
Engineering or creating tissues for therapeutic use, like pieces of cartilage for knee repair, is challenging. The chemicals and forces used to coax cells into the desired shape can impair their function once implanted. at the French National Centre for Scientific Research (CNRS) and his colleagues discovered a contactless way to make stem cells form spheroids using ultrasound. Hoyos will present the work at the 182nd meeting of the Acoustical Society of America in Denver, Colorado on 23 May.
After filling a small, long tube with a solution full of stem cells, the team played an ultrasound wave at one end. This reflected at the other end, creating a pattern known as a standing wave, where the fluid repeatedly oscillated up and down but not back and forth. Stem cells settled into the parts of the wave that moved the least.
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The team expected to see stem cells levitating in the solution in flat layers. 鈥淲e were very surprised when, after some hours, these layers started to shrink and form three-dimensional objects. After 24 hours, they became similar to spheres,鈥� says Hoyos.
When stem cells are levitated by ultrasound, they don鈥檛 touch any surfaces, such as tissue scaffolds commonly used for growing the cells. The result of this contactless development seems to be that the cells organise themselves into shapes like those that occur in the body鈥檚 tissues.
Nutrients constantly flowed through the team鈥檚 device, which kept the cells alive while they were levitating. This means that they were, in theory, ready to be implanted in a person. Hoyos and his colleagues are already working on using ultrasound levitation to grow clumps of liver cells and endothelial cells, which line the insides of blood vessels. They hope that these could be used for transplants one day.
at the George Washington University in Washington DC says that, while cells have been levitated by sound before, seeing them curl up into tiny balls is new. To use them in medicine, he says, researchers will have to better understand the biological that guide this behaviour and how they could be controlled.
