Cell: Harvard scientists did a study of chicken skins...

Why do we get goose bumps? If you've ever been curious about this, you're as curious as Darwin.
Darwin also thought about chicken skins in his writings on human evolution.
he noticed that animals raised hair, feathers, or thorns to regulate body temperature, courtship or attack, which helped to improve survival.
But for humans, the straight sweat ingenuity seems to have no benefit, why has it been preserved in evolution? A recent study published in the leading academic journal Cell found the answer.
Professor Xu Yajie of Harvard University and his co-authors found that the cells that make chicken skins had another important function: promoting hair growth.
talk about the process of chicken skin production, it has long been known that this requires the nerves around the follicles and small muscles to work together: cold or other external stimulation, triggering sympathetic nervesignals to signal, and then the vertical hair muscles through contraction, so that hair in the hair follicles up.
However, when the researchers examined the skin of mice using a high-resolution electron microscope, they found that the sympathetic nerves were not only connected to the vertical muscles, but also to hair follicle stem cells.
rather, nerve fibers are wrapped around hair follicle stem cells like ribbons, while the vertical muscles act as "stents."
", neurons generally regulate excitable cells, such as other neurons or muscles, through synaptic structures.
But we were surprised to find that they formed a synaptic structure with epithelial stem cells, which is not a typical target for neurons.
," said Professor Xu Yajie.
around hair follicle stem cells, nerves and muscles form a microenvironment: sympathetic nerve secretion neurotransmitters dominate hair follicles, and the vertical hair muscles support the sympathetic nerves (Photo Source: References 1)) Further analysis shows that these sympathetic nerves secrete by de-epinephrine, regulating the activation of hair follicle stem cells, thus having an important impact on hair growth.
in the hair growth cycle of adult mice, hair follicle stem cells switch between activation and rest: in an active state, promote cell proliferation and convert to hair;
considering that in cold stimulation, the sympathetic nerves become more active and produce more norepinephrine, does this mean that cold not only allows the skin to get goose bumps, but also promotes long hair by stimulating hair follicle stem cells? To test the idea, the team designed a set of experiments that allowed some mice to live in a 5-degree cold.
just 2 hours, the mice developed a typical "chicken skin" reaction, with hairs erected, indicating that the sympathetic nerves and vertical hair muscles around their skin hair follicles were normally compatible.
over time, it can be seen that the sympathetic nerves continue to activate, producing more norepinephrine, causing hair follicle stem cells to be activated more quickly and advance into the regeneration phase.
, by 2 weeks, long periods of cold stimulation allowed mice to grow hair faster than mice living in a 30-degree warm environment.
short exposure to cold causes mouse hair to stand up; mice exposed to cold for 2 weeks in a row, with new hairs growing faster on the back (Picture source: References) "We can see that there are two layers of reaction to temperature changes in the outside environment: chicken skin (vertical hair) is a quick way to provide relief in a short period of time, but if the cold persists, this mechanism lets the stem cells know that it's time to grow a new layer of hair.
" dr. Yulia Shwartz, lead author of the study, summed it up.
References: (1) Yulia Shwartz et al., (2020) Cell Cell Type Promoting Goosebumps Form a Niche to Regulate Hair Folcle Stem Cells. Cell. DOI:
the real reason behind the goosebumps. Retrieved July 21, 2020 from.