There is more to melanocytes than skin colour

Last Updated on 12th January 2023 by Caroline Haye

The secret life of our pigment-producing cells

The majority of people on the planet would probably have no idea what melanocytes are. But if you have vitiligo, or any other pigmentary disorder, you will know that they are melanin-producing cells. You will also be aware that melanin is the pigment that provides colour and UV protection to our skin. But did you know that there is a lot more to them than that? If your answer is no, don’t feel bad. Not even the experts have learned all there is to know about these surprising little cells. Read on, and you will be rewarded with a glimpse into their intriguing secret life.

What exactly are melanocytes and how are they involved in vitiligo?

“Melanocyte” is the name given to a varied group of cells that derive from the “neural crest”. (This is the source of most of the cells that go on to develop and make up the peripheral nervous system). Their role in producing melanin is well known. So it comes as no surprise that damage inflicted on them in vitiligo should result in loss of colour from the skin. But melanocytes also have other, less well known, physiological functions to perform, many of which are unrelated to pigmentation. This means that, whilst white spots may be the most obvious symptom of vitiligo, they are highly unlikely to be the only one. So, the next time someone tells you that vitiligo is a purely cosmetic condition, you might want to take their opinion with a pinch of salt.

Where are melanocytes found?

All melanocytes have the ability to produce melanin. They are present in our skin, hair follicles and eyes. All these areas are pigmented. So, it is to be expected that they should contain melanin-producing cells. What may be more surprising is that they are also to be found in our mucosal membranes. These are the moist surfaces that line our insides. They include the thin tissue that forms the surface of the vagina, as well as inside the inner ear, the heart, bones, and the meninges. (The meninges are three protective layers that line the skull and protect the brain and spinal chord). It is hard to imagine why these areas would need to have any pigment. So, if you are wondering what pigment-producing cells are doing in these parts of the body, then read on.

What other functions do melanocytes have?

Melanocytes and the immune system

One of the most crucial functions of melanocytes is as an integral part of our immune system. They defend the epidermis from inflammation. Working together with their close partner cells, keratinocytes, they maintain healthy skin regeneration. This protects the skin against any invading microbes. Damage to either of these two types of cell can therefore leave the skin open to infection and inflammation. And one of several possible responses to this kind of attack is depigmentation. (For more on this, take a look at this article: What are melanocytes really doing all day long…? )

Melanocytes and hearing

More research needs to emerge before anyone can be completely sure what else our melanocytes are busy doing. But their protective role must surely be a key one, given that their distribution throughout the insides of our body is obviously intended for some purpose other than helping us get a suntan. In the inner ear they act together with other cells to ensure that our auditory hair cells function properly. This is why damage to melanocytes in cases of vitiligo can lead to some hearing loss. According to estimates, some 12% to 38% of vitiligo sufferers experience varying degrees of deafness as a result of this.

Melanocytes and vision

Science knows less about ocular melanin than melanin in the skin and hair follicles. What we do know is that melanocytes in the iris regulate the amount of light that enters the eye. And those behind the retina act as a block to prevent light from penetrating deeper into the tissues behind. Ocular abnormalities in vitiligo, including changes in vision and tear production, can sometimes occur for this reason. An estimated 30 – 40% of vitiligo patients have some loss of pigment in their eyes. Despite this, significant loss of eye colour or vision are, thankfully, rare.

Melanocytes in our bones, internal skin and organs

Presumably the colour of our heart, bones, brain and mucous membranes does not serve any useful purpose. Neither are these areas of the body exposed to UV light, so they don’t need protection from this. So the role of melanocytes here must be quite different from that in the skin and hair follicles. Some research has been conducted into the wider role of melanocytes and their diseases but the results are hard for a lay person like myself to understand. And, in any case, they are scarce and relatively inconclusive.

So, rather than try to delve into the complex science involved, I shall simply indulge in a bit of amateur speculation. Why would the cellular damage that leads to vitiligo confine itself to the melanocytes in our skin and hair follicles? It seems more likely that it would happen wherever they occur in the body. And surely there would be consequences to this. Hopefully, not dire ones, but they might be enough to produce symptoms beyond white patches on the skin.

White patches may be just one of many vitiligo symptoms

Many people who contact me to talk about their vitiligo tell me that they have other chronic health problems too. And, unless these fall into the category of known autoimmune conditions, they probably assume these ailments are completely unrelated to their vitiligo skin. Of course, a lot of them no doubt are unrelated. But could some of them be the result of cellular damage affecting melanocytes throughout their system?

Allergy symptoms

For example, many people with vitiligo (myself included) have a history of allergies. I wonder if some allergy symptoms might actually be a result of melanocyte damage in our mucous membranes. This could perhaps leave the lining of our ear, nose, throat and sinuses prone to irritation, causing inflammatory and immune responses.

Another symptom I sometimes wonder about is a burning sensation in the throat when drinking tap water. As this water typically contains chemical additives maybe it is not surprising it should cause irritation to over-sensitive mucous membranes. Some women even report a similar burning sensation in the vagina when taking a bath. And so many of us suffer from irritable bowel symptoms that I have to wonder if an over-sensitive gut lining could be the result of melanocyte damage here too.

Endometriosis and other gynaecological problems

Several women have asked me in the past if I know of any link between their vitiligo and their endometriosis. I was not aware of any direct link. But reading an article called Melanin-containing Cells of the Endometrium makes me realise that such a link might well exist. The involvement of melanocytes in ovarian tumours (a fact I was unaware of when I had surgery for this a few years ago) begs a similar question. I am not knowledgeable enough to answer these questions. And I certainly don’t want to suggest that having vitiligo carries a high risk of any of these conditions. But I do think that they are questions worth asking.

Arthritis

Unlike rheumatoid arthritis, osteoarthritis is not considered to be an autoimmune condition. But I have a history of osteoarthritis. And joint pain and stiffness seem to be a recurring theme among the vitiligo friends I speak to. These could simply be in line with average levels of arthritis among the general population. Or might they have something to do with the melanocytes in our bones and connective tissue? No doubt, your doctor and mine would laugh at the suggestion. But the fact is that very little research into this exists, so it has to remain a possibility. An article about a pigmentary disorder called Ochronosis, explaining its impact on cartilage and bones, was the only information I found that seemed at all relevant.

Brain and nervous system

Why would melanocytes in the brain and nervous system be immune from attack in vitiligo? And what might the effect be of any such damage? The role of melanocytes in the brain is a little-understood topic, as far as I can tell. A paper called Melanocytes: a window into the nervous system sounded as if it might shed light on the subject. But it proved too complex for me to really understand. The only indication it gave me was that that talking about pigment-producing cells in the context of the nervous system is clearly not as outlandish a concept as it may sound. Perhaps something in this science is what led to the so-called “neural theory” of vitiligo. That early theory has fallen out of favour but there is nothing to say that it may not still have some basis in fact.

Heart and lungs

The presence of melanocytes in our heart and plumonary veins is yet another example of their mysterious secret life. What role they play there is not very clear. An article, published in the Journal of Clinical Investigation, points to the involvement of “melanocyte-like cells” in cases of cardiac arrhythmia (irregular heartbeat). Again, the science is way beyond my comprehension level. But the gist is enough to keep me pondering the same question. What might the possible unseen and under-researched effects of vitiligo throughout our internal organs be?

Why I chose this blog topic

Regular visitors to this blog will know that I am not in the habit of covering depressing topics. This is a place for good news and optimism. And we really do have plenty of reasons to focus on the positive. I did not chose this subject in order to alarm anyone. If having vitiligo significantly increased the risk of developing life-threatening diseases, I am sure this would have been evident a long time ago. It would no doubt have received more timely attention from the research and medical professions too. It is far more likely that, if melanocyte damage does in fact occur throughout the body, it leads to a variety of non-life-threatening and seemingly unconnected low-level ailments.

I am not suggesting we should obsess about all of the complications that may or may not result from having vitiligo. I do believe, though, that we ought to reject a view of vitiligo as a primarily cosmetic condition that only affects skin colour. We ought instead to recognise that a disorder that attacks healthy melanocytes might have implications beyond white patches. Given how widespread and multi-tasking these amazing cells are, it seems a logical possibility that the fabric and function of our entire internal lining, organs and immune system may also be compromised to some extent.

I don’t pretend to have any deeper understanding of this subject beyond my own very basic logic and some simple fact-finding. But, as increasingly sophisticated vitiligo research continues at an exciting pace, more answers are bound to emerge and we will gain more detailed knowledge about all aspects of the condition. Maybe then the fascinating secret life of melanocytes will become less of a secret, although I am certain it will prove to be even more fascinating than we imagined.