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Scientists discover a hidden way that humans feel and sense touch

Scientists have unveiled a fascinating discovery about the sense of touch, identifying hair follicles as previously unrecognized touch receptors. This breakthrough offers new insight into our sensory experience and might reshape our understanding of certain skin conditions.

Surprising twist in sensory biology

Researchers from Imperial College London recently discovered that cells within hair follicles, previously acknowledged solely for their role surrounding hair fiber, possess the ability to sense touch directly. This finding counters the traditional understanding that only specific nerve endings in the skin are responsible for sensing touch.

“Our findings are quite surprising,” explains Dr. Claire Higgins, lead author of the study from Imperial’s Department of Bioengineering. “We’re venturing into uncharted territory by discovering this unique role of hair follicle cells in processing light touch, an area traditionally reserved for specific nerve endings.”

Delving into the science of touch

The sense of touch has always been believed to be processed through various complex mechanisms:

  1. Sensory nerve endings in the skin: These nerve endings detect touch and relay these signals to the brain for interpretation.
  2. Hair follicles: These structures, rich with nerve endings, sense the movement of hair fibers.
  3. Special sensory nerves in hairy skin (C-LTMRs): These nerves process the emotional aspect or the ‘feel-good’ sensation associated with touch.

The new research indicates an additional, unexpected participant in this sensory experience: the hair follicles themselves.

Innovative methodology

The team’s journey to this discovery involved analyzing single-cell RNA sequencing data from human skin and hair follicles. Astonishingly, they noticed that hair follicle cells contained a significantly higher percentage of touch-sensitive receptors compared to their counterparts in the skin.

To further investigate, the researchers established co-cultures of human hair follicle cells and sensory nerves. Upon mechanically stimulating the hair follicle cells, they observed an activation of the adjacent sensory nerves. This was a crucial indication that hair follicle cells themselves could respond to touch stimuli.

Neurotransmitters and the sense of touch

Seeking to understand the communication between hair follicle cells and sensory nerves, researchers employed a technique known as fast scan cyclic voltammetry. They discovered that when stimulated, hair follicle cells released two key neurotransmitters: histamine and serotonin.

“These neurotransmitters were crucial in the signalling process,” Dr. Higgins notes. “When we inhibited their receptors on the sensory neurons, the neurons ceased to respond to hair follicle cell stimulation.”

Additionally, interference with the synaptic vesicle production in hair follicle cells disabled these cells from signalling the sensory nerves, further confirming the integral role of these neurotransmitters.

Implications for skin conditions

In parallel experiments involving skin cells, researchers found that while these cells released histamine in response to light touch, they did not release serotonin. This revelation has significant implications, especially in understanding skin conditions such as eczema traditionally linked with histamine release.

“We always presumed immune cells were the sole histamine contributors in conditions like eczema,” Dr. Higgins remarks. “Identifying this new role of skin cells could be a game-changer for dermatological research.”

Digging deeper ito the sense of touch

While these findings from cell cultures mark a significant step forward, replicating them in living organisms is the next critical phase. The team is also curious about exploring whether hair follicles activate specific types of sensory nerves, particularly since C-LTMRs are exclusive to hairy skin.

“We’re on the brink of potentially uncovering a unique signaling mechanism,” Dr. Higgins anticipates. “There’s a whole new exciting path of research ahead of us.”

In summary, this study not only broadens our comprehension of sensory biology but also opens up new avenues for therapeutic research, particularly concerning skin disorders. The touch, one of the fundamental senses, still holds many secrets. Studies like this are key to unlocking them.

The full study can be downloaded from Imperial College London.

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