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Hair Follicles Help Guide Nerves

When the skin is wounded, many structures in the skin get damaged. Nerves, for example, get damaged and need to regenerate.  The ability of nerves to regenerate is very important to enable us to get sensation or 'feeling' back in the skin.

Recently, a fascinating research study was published which looked at a simple question – Do hair follicles have a role to help nerves to regenerate?

To answer this question, we need to back up a bit. It’s important first to understand that the hair follicle is not just a strand of keratin that somehow roots itself deep down under the skin. Rather, the hair follicle is an extremely complex structure that is richly innervated with nerves. Nerves wrap themselves around hair follicles. In the past, several researchers showed that hair follicles do, in fact, have an extremely important role in the way nerves grow and connect in the skin.

In a new study, researchers used a tissue engineered skin model to show that newly growing hair follicles helped newly growing nerves (neuritis) move about in the skin.  What was interesting was that newly growing nerves didn’t just connect up in a haphazard way, but rather seemed to be located around growing hair follicles and even within them.   The researchers concluded that growing hair follicles essentially ‘attract’ nerves and help to guide the way they develop.

Figure 1: Hair follicles play a key role to help nerve migration

To use an analogy, I like to think of hair follicles as traffic police working in an extremely chaotic traffic jam.  Without the traffic police, cars don’t move well. Without hair follicles, newly developing nerves in the skin don’t move well either. When traffic police are present, the cars move around the roads more efficiently.

Reference

Gagnon V et al. Hair follicles guide nerve migration in vitro and in vivo in tissue-engineered skin. J Invest Dermatol 2011; 131: 1375-8

Botcharev VA et al. Hair cycle-dependent plasticity of skin and hair follicle innervation in normal murine skin. J Comp Neur 386; 379-95

Zhang Y et al. Activation of beta-catenin signalling programs embryonic epidermis to hair follicle fate. Development 2008; 135: 2161-72.