Researchers using mouse models have identified a previously unrecognized class of fine hairs, called vellus-like hairs, and a specialized population of neurons that innervate them. These hairs resemble human peach fuzz. The work, supported in part by the National Institutes of Health, is published in the journal Neuron.
In mice with chronic skin inflammation, a condition similar to eczema in humans, animals with the touch-sensitive neurons showed normal scratching. Those that lacked the neurons or had them inactivated exhibited a markedly reduced scratching response. The team mechanically stimulated itch by stroking the vellus-like hairs with a small loop of thread. They also made the identified neurons sensitive to blue light and showed that light alone could trigger scratching, confirming the neurons’ role in mechanical itch.
Researchers identified proteins that convey the itch signal from hairs to the spinal cord, and human neurons grown in culture responded to the same proteins. Because many treatments ease chemical itch but not inflammation-driven itch, the team argues that targeting the mechanical itch pathway could be more effective for chronic itch. Earlier work also indicates that spinal cord "gating" circuits can block mechanical itch unless it is activated in a particular way.
- Discovery: vellus-like hairs and connected neurons.
- Tests: thread stroke and blue-light activation.
- Implication: a new treatment target for chronic itch.
Difficult words
- vellus-like hairs — very fine soft hairs similar to peach fuzz
- innervate — to supply nerves that connect to a body part
- chronic — lasting a long time or recurring regularly
- mechanical — caused by touch or physical stimulation
- inactivate — to make something stop working or activeinactivated
- spinal cord — nerve bundle inside the spine that carries signals
- pathway — series of cells or structures that transmit signals
- convey — to carry or transmit meaning or signals
- culture — cells grown in laboratory conditions for study
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Discussion questions
- How might treatments that target the mechanical itch pathway change care for people with chronic skin inflammation?
- What are possible difficulties when applying results from mouse models to human patients?
- The article mentions spinal cord "gating" circuits. What risks and benefits could come from trying to alter those circuits to reduce itch?
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