Researchers have, for the first time, coaxed human stem cells to become sensory interneurons – the cells that give us our sense of touch. The new protocol could be a step towards stem cell-based therapies to restore sensation in paralysed people who have lost feeling in parts of their body, researchers at the University of California, Los Angeles (UCLA) in the US said.
Sensory interneurons, a class of neurons in the spinal cord, are responsible for relaying information from throughout the body to the central nervous system, which enables the sense of touch. The lack of a sense of touch greatly affects people who are paralysed. For example, they often cannot feel the touch of another person, and the inability to feel pain leaves them susceptible to burns from inadvertent contact with a hot surface.
“The field has for a long time focused on making people walk again,” said Samantha Butler, associate professor at
UCLA. “Making people feel again does not have quite the same ring. But to walk, you need to be able to feel and to sense your body in space; the two processes really go hand in glove,” said Butler, who led the study published in the journal Stem Cell Reports.
In a second study, published in the journal eLife, Butler and her colleagues discovered how signals from a family of proteins called bone morphogenetic proteins, or BMPs, influence the development of sensory interneurons in chicken embryos. The first study applies those findings to human stem cells in the lab.
When the researchers added a specific bone morphogenetic protein called BMP4, as well as another signalling molecule called retinoic acid, to human embryonic stem cells, they got a mixture of two types of sensory interneurons. DI1 sensory interneurons give people proprioception – a sense of where their body is in space – and dI3 sensory interneurons enable them to feel a sense of pressure.
The researchers found the identical mixture of sensory interneurons developed when they added the same signalling
molecules to induced pluripotent stem cells, which are produced by reprogramming a patient’s own mature cells such as skin cells. This reprogramming method creates stem cells that can create any cell type while also maintaining the genetic code of the person they originated from.
The ability to create sensory interneurons with a patient’s own reprogrammed cells holds significant potential
for the creation of a cell-based treatment that restores the sense of touch without immune suppression.