An Imperial expert in tissue regeneration has been turning her attention to our crowning glories.

Dr Claire Higgins from Imperial’s Department of Bioengineering carries out research to understand the mechanisms behind how tissue develops and regenerates. Her aim is to determine how some parts of the body regenerate when we are well and how the process copes with disease and injury. 

Hair is one of the few parts of the body that can regenerate itself, which has the advantage of not leaving behind any damage to tissue

Some of Dr Higgins’s work focuses on hair follicles, as she believes that unravelling the mysteries behind their ability to regenerate could ultimately lead to new ways of healing the body. She talked to Colin Smith about her research, as well as some general facts about people’s luscious locks.

Why are hair follicles useful to study?

When the body is recovering from disease or injury it heals itself, but this causes scarring.  We think of a scar as something on the skin because it is visual. However, scars form in all tissues after injury and this affects how they function.  For example, after a heart attack, cells called cardiomyocytes, which produce heart muscle, get replaced by scar fibroblasts, and this impairs how the heart beats. 

Interestingly, some parts of our body opt not to heal and instead undergo a regeneration process. This has the advantage of leaving no scarring. As a consequence tissue function is not impaired. The drawback however is that only a few parts of our body can do this. The liver can regenerate itself and so can hair follicles. 

We are studying follicles to try and understand how they have the ability to regenerate and not scar after injury. Compared to the liver they are much easier to access and explore. We hope to use the insights from our research to promote scar free healing, or perhaps engineer follicles in situations where there are none, such as after a burn, following a skin graft or to even improve hair transplantations.

What does this regeneration mean for the aging process?

The regeneration process does not prevent hair from aging. When follicles get older they lose their regenerative capacity and start to shrink. As a consequence the cell population responsible for follicle regeneration disappears. This has a knock-on effect where stem cells in the follicle fail to become activated.  Combined, these processes lead to production of a smaller hair fibre, and eventually no fibre at all and hair loss.

Alternatively, follicles can just get stuck for prolonged periods in a resting state where they are not producing a hair fibre. 

The concept of aging for hair may sometimes seem strange because follicles can be deceptive. For example, we think of an aged follicle as one that produces a grey or white hair. However, very young people can go grey and appear to have aging follicles, while very old people can have a full head of hair without any greys.

Greying is not always linked to age and is actually caused by a reduction in melanocyte cells, which create pigment, in the follicle over time. Melanocytes are very sensitive to environmental and cellular stresses.  Over time these stresses increase, and this leads to the death of melanocytes.  Since they are no longer around to create pigment, hair turns grey then white.

Are all types of hair loss the same?

No, there are very different forms of hair loss.  The most common form that nearly everyone will have heard of is androgenetic alopecia, also known as male or female pattern hair loss. Another example is the hair loss that mothers often go through around three months after giving birth, which is called postpartum hair loss, or telogen effluvium.  Alopecia areata is an autoimmune form of hair loss where the body’s immune system attacks the hair follicle.  This condition shares similarities with other autoimmune disorders such as Type 1 diabetes and rheumatoid arthritis, where the immune system attacks the pancreas or the joints.

What do you think is the future of hair transplantation?

There is a small cluster of cells at the base of the follicle that are capable of instructing growth of a new follicle, and if they are removed and placed into non-hairy skin they will induce growth of a new follicle in this location.

Theoretically, these cells could be removed from a single follicle, expanded in number, and then used to instruct growth of multiple follicles in a new location.  Using these cells to instruct new hair growth is the first hurdle to overcome.  After this, the influence of these cells would need to be fine-tuned to regulate the size and curvature of the induced follicle, and the length and colour of the resultant hair fibre. 

We’re interested in exploring this as an alternative to the kinds of hair transplants that occur now, which require enough donor follicles to be present for transplant in the first place, and which require removal of follicles from the back of the scalp, which is a painful procedure.

Getting back to the different traits of hair, why do people have curly hair and some people have straight hair?

Hair curl is defined by the curvature of the hair follicle beneath the skin surface.  There is a strong genetic component to hair shape, given that in sub-Saharan Africa only curly hair, not straight hair is observed. 

Straight hair appears to be a relatively new trait in humans. It is thought to have evolved in the past 65,000 years, specifically when people were migrating from Africa to Asia and later into Europe.  Straight hair must have conferred an evolutionary advantage for people leaving Africa, and there are many theories as to what that advantage was.  A popular theory is that straight hair, which is densely packed, bestowed extra warmth to the scalp in cold climates, which would have been a disadvantage in hotter climates. 

Why are some people blonde and some people brunette?

Unless your hair colour comes out of a bottle, your hair colour is down to genetics.  Blonde hair has evolved twice as it is found commonly in populations of northern Europe, but also in the Solomon Islands in Melanesia.  In Europe, it is thought to have evolved about 11,000 years ago, due to variants in a gene called MC1R. 

In brown and black hair, melanocytes produce the dark pigment eumelanin, while in blonde hair there is a less eumelanin and higher levels of a lighter pigment known as pheomelanin, giving the range of blonde pigments commonly observed in individuals.

Interestingly, Asian hair is glossier compared to Caucasian hair because of the structure of the fibre. Asian hair fibres have a more rounded diameter, which means they reflect more light, compared to Caucasian fibres, which are more ovoid.