The Fascinating Science Behind Touch Perception

Monday - October 30 2023, 13:22 UTC - 1 year ago

Researchers from Imperial College London discovered that cells in hair follicles may sense touch and release neurotransmitters serotonin and histamine, which might explain the mechanism behind chronic skin conditions like eczema. They are now working on developing imaging techniques to monitor the release of serotonin and histamine in real time.

A sophisticated and vital component of human perception, the sensation of touch enables our interaction with the physical world. Touch perception consists of several essential elements.

Firstly, it is greatly influenced by skin, which is the greatest sensory organ in the human body. Skin has different layers, such as the dermis and epidermis, that contain different kinds of mechanoreceptors that respond differently to different kinds of touch stimuli.

Detecting mechanical stimuli .

Mechanoreceptors are specialized nerve cells that are responsible for detecting mechanical stimuli such as pressure, vibration, stretching, and distortion.

Mechanoreceptors translate these mechanical stimuli into electrical impulses which are sent to the brain and spinal cord, part of the central nervous system (CNS), which receives these electrical signals via sensory nerves. The CNS then processes these signals in what we perceive as touch.

Now, according to recent research from Imperial College London, cells in hair follicles—the structures that encircle the hair fiber—may also sense touch. This is according to studies done in cell cultures.

"This is a surprising finding as we don’t yet know why hair follicle cells have this role in processing light touch. Since the follicle contains many sensory nerve endings, we now want to determine if the hair follicle is activating specific types of sensory nerves for an unknown but unique mechanism," said lead author of the paper Dr Claire Higgins, from Imperial’s Department of Bioengineering.

Additionally, the researchers discovered that in reaction to contact, these hair follicle cells release the neurotransmitters serotonin and histamine. These discoveries may one day aid in our understanding of the function histamine plays in inflammatory skin conditions like eczema.

In order to conduct the study, the scientists examined single-cell RNA sequencing data from human skin and hair follicles. They discovered that, in comparison to analogous skin cells, hair follicle cells had a greater fraction of touch-sensitive receptors.

Furthermore, human hair follicle cells and sensory nerves were co-cultured, and when the hair follicle cells were mechanically stimulated, the researchers discovered that this caused the nearby sensory nerves to become activated.

Same procedures with different cells .

The researchers then proceeded to conduct the same procedures with skin cells. They found that the cells released histamine in response to touch, but not serotonin.

"This is interesting as histamine in the skin contributes to inflammatory skin conditions such as eczema, and it has always been presumed that immune cells release all the histamine. Our work uncovers a new role for skin cells in the release of histamine, with potential applications for eczema research," Higgins said.

Now, the researchers hope to ascertain whether particular kinds of sensory nerves are being stimulated by the hair follicle and whether hair follicles have a special means of communicating with these nerves that we are still unaware of. Additionally, the study was conducted in cell cultures, and in order to validate the results, the scientists are now working on developing imaging techniques that will enable them to monitor the release of serotonin and histamine in real time.