Turning on its Head

Endometriosis is usually described as some variation of ‘patches of endometrium-like tissue growing elsewhere in the body’. This description though throws up several questions. For example, if endometriosis is related to the normal endometrium, what can this tell us about the disease and what is the connection between the two tissue types?

Initially the similarity of endometriosis to the normal endometrium led academics to believe endometriotic lesions were seeded in their locations by the backward flow of endometrial cells during menstruation. This made sense at the time because backward flowing menstruation (retrograde menstruation) is a thing that happens and the fact that endometrial cells were entering the pelvic cavity and endometriosis appeared to be endometrial in character seemed too much of a coincidence.

However, retrograde menstruation occurs almost universally in women of reproductive age, yet endometriosis affects around 10% of women, so clearly there was still something missing from this argument. Maybe the normal endometrium of women destined to have endometriosis is somehow different from other women. These days technology is such that we can analyse thousands of properties of cells at the molecular level, allowing an unprecedented degree of detailed characterisation of all the tissue types in the human body. Several studies have focussed on characterising the endometrium of women with and without endometriosis and found that; yes the endometrium in women with endometriosis is indeed different. The endometrium from women with endometriosis appears to have a higher ability to survive, proliferate and invade, seemingly filling in the missing part of the retrograde menstruation theory.

But, like all great mystery stories, the case is never wrapped up in a neat little package so early on. In recent years more and more evidence is coming to the fore, challenging the theory of retrograde menstruation. In particular there is now quite a significant amount of evidence to show the displaced endometrium that defines endometriosis is, in fact, present before you were even born. There are also rare documented cases of endometriosis in men, women who cannot menstruate and non-menstruating primates; so clearly there is the need for some radical re-thinking.

Maybe we’ve had the whole thing upside-down; maybe it is not the endometrium that dictates the fate of endometriosis, but endometriosis that dictates the fate of the endometrium. A collaborative research effort has provided some evidence to this very end (you can read the full article here). The authors of this study experimentally induced endometriosis in baboons by injecting endometrial cells into the pelvic cavity and letting them form endometriotic implants. They then compared the expression of genes within the endometrium of the baboons with experimentally induced endometriosis and disease free baboons over the course of 16 months. What they found was that the presence of endometriosis (even in its very early stages) led to marked changes (a total of 4,331 genes were altered) in the normal endometrium.

This potentially turns accepted wisdom on its head, in that women with endometriosis are not born with a defective endometrium that gives rise to endometriosis via retrograde menstruation. Rather, if we are to take all the above evidence into account, it appears endometriosis is a condition you are born with that, when the endometriotic implants ‘mature’ lead to changes in the function of the normal endometrium, thus perhaps also accounting for the fertility issues women with endo suffer from.

However, one big questions still remains – how does endometriosis communicate with the normal endometrium to illicit these changes?  If we disregard the notion that endometrial cells can display quantum entanglement then there must be a signalling pathway between the two cell types. The first idea that comes to mind is something to do with the production of inflammatory factors by endometriotic lesions. Lesions produce a number of inflammatory factors that are also regulators of gene expression which, hypothetically, could travel to the normal endometrium and alter its gene expression, but that’s just an educated guess.

Even with new evidence making us rethink the development of endometriosis, invariably we find ourselves with more questions than answers - for example:

If the endometriotic implants are removed, do the changes to the normal endometrium revert back, or are the changes induced by endometriosis permanent?

If displaced endometrium is found before birth, how does it get there? Müllerianosis? Mesenchymal stem cells? Both? Something else?

What are the genetic/epigenetic/environmental factors that influence the displacement of endometrial cells?

Why does endometriosis only occur in certain primates species?

Does retrograde menstruation have any role to play in endometriosis and if not, why not? Could some cases of endometriosis be due to retrograde menstruation and others not, meaning there are multiple pathways to endometriosis development?

There is still a long way to go before we completely comprehend endometriosis, but with each passing year the walls blocking our understanding are chipped away until eventually, the truth will be revealed.

In the Genes

I recently read, with great interest, several stories (also here) about a new study into the genetics of endometriosis published by an international research effort based in Australia (better summary here). Most of the news items centred around a headline involving an announcement like ‘new genes linked to endometriosis’, or something along those lines. As my background is in human genetics I was keen on looking up the study at the centre of these reports. This particular study (link to abstract here) was looking at what gene/s may be related to endometriosis in women of Japanese and European ancestry. This was quite a large study as well, including 4,604 women with endometriosis and 9,393 controls, a far greater number of any other such investigation. 

Lots of studies on the genetics of endometriosis have been done in the past, mostly with slightly disappointing results. This is mainly because we haven’t yet been able to find a genetic link to endometriosis that is common amongst all women of all races.

But before we go any further into that study, or its results, I think I should go over some of the basics about why genetics is important and why we should bother looking for endometriosis related genes.

Let me ask you something, when an item in your house (Like a fridge, cooker or energy dispersive x-ray diffracter, for example) malfunctions what is the first thing you do? If your answer is “buy a new one” congratulations, you have more money than me. But we less monetarily endowed people tend to look at the instruction manual to try and figure out what’s gone wrong. The human body is similar in that way, because we too, have an instruction manual and that manual is called our DNA. 

This stuff - Image courtesy of Freedigitalphotos.net

 DNA is a long, twirly, helix like substance found in nearly every cell in your entire body, it’s the set of instruction that made you. But DNA isn’t written in any normal alphabet, no the DNA alphabet is written in an alphabet consisting of only four letters (A,T,G and C) which make up words, some thousands of letters long,  which we refer to as ‘genes’. Each gene codes for making a certain protein and there are tens of thousands of genes in your DNA instruction manual making almost one hundred thousand proteins.

That’s all fine and dandy, but when a cell divides it has to copy every single letter of the DNA manual, all 3 billion letters, and your cells have divided many, many times before you are even born. So, despite some astonishing cellular proofreading, errors start to creep into your DNA; most are harmless, rarely they are beneficial, sometimes they are harmful (we call these errors ‘mutations’). If these mutations occur in a gene (or number of genes), it can corrupt the way the protein product of that gene functions, hence causing cells to behave in odd/dangerous ways leading to, what we know as, a disease. So when a disease occurs in a group of people, we can look at their collective DNA to see if they share any common mutations.

This is what the aforementioned study was looking at: common mutations in DNA amongst women with endometriosis of European and Japanese descent; this would hopefully allow us to begin picking apart how and why endometriosis arises in some women and how it is passed on through generations. Mutation comes in different types though and the particular mutations this latest study was looking for were called SNPs (which stands for Single Nucleotide Polymorphism, not Scottish Nationalist Party, for all our Caledonian readers). This type of mutation is when only a single letter of your DNA is changed and, though you wouldn’t think changing one letter out of 3 billion would make a difference, it can have wide reaching implications.

Anyway this latest study found several of these ‘SNPs’ that were common amongst women with endometriosis. Unfortunately they all have terribly unmemorable names, such as ‘rs12700667’, ‘rs7521902’, ‘rs13394619’ and ‘rs10859871’, but who cares because now they’ve found these mutations, we can start getting a better understanding of endo leading to better diagnostics and treatments right? Well, yes and no.

One of the troubles is that, unlike some diseases which are caused by a mutation in a single gene, endometriosis is related to mutations in lots of different genes (what we call, polygenic). Now the more genes you add to the picture the more complicated it becomes because you have to take into account the function of each gene in the wider context of the disease. This information will eventually offer us some great insights into how endometriosis works, but figuring out all the connections may take some time. 

This, for example, is the interaction network for just ONE gene: Source - Wikipedia

There’s another issue as well, genes aren’t the only thing DNA is made of - far from it.  You see, genes make up only around 2% of your DNA, so what is the rest of it there for? For a long time it was thought the DNA that didn’t have genes was just ‘junk’, it had not function, a remnant of our evolutionary past and graveyard of ‘dead’ genes.  However, recently we have come to understand that this ‘junk’ DNA has a lot of other, very important, things lurking in it. Some of these things act as ‘switches’ for genes, basically controlling whether a gene is on or off inside a certain cell. So it’s not just about the function of a gene, but the regulation of it as well.

In this latest study, several of the mutations they identified weren’t in genes at all, but were instead found in DNA around them, which unfortunately complicates the matter further because now we have to figure out what implications this has on gene regulation as well as function.

So, where are we at the moment? The diagram below shows where we are and how far we have to go before we have a complete understanding of endometriosis. 

Simple as that!

Although we are far from understanding endometriosis in its entirety, studies such as this latest one have opened the door and pointed the way forward for us. It’s going to take more time and a lot more effort, but then, nothing worth doing was ever easy.

That’s an awful lot of Red Wine

I’ve noticed recently there have been a couple of articles published about a compound called resveratrol and its effects on endometriosis.  Resveratrol is a compound found in many different types of plant, but mostly red skinned fruit such as grapes. In recent years it has attracted much attention due laboratory tests showing it to have potential as an anti-cancer drug. Most of the work is in its early stages though and there are a lot of kinks to be worked out before resveratrol, or drugs based on it, will appear in hospitals. Nevertheless many people are investigating resveratrol for many different reasons.

In case you were wondering, this is what resveratrol looks like

For example, resveratrol has been suggested to have a whole range of beneficial properties such as anti-inflammatory, antiviral, antidiabetic, cardio and neuroprotective effects so it seemed only a matter of time before someone would start investigating whether this compound could be used against endometriosis.

The first such study comes from Argentina and looked at the effect of resveratrol and another compound, EGCG (which is found in green tea) on endometriosis that had been surgically induced in mice. What they found was that, in mice given these two compounds, the number, size and growth of the endometriotic lesions was reduced significantly. This is quite an encouraging result, but animal models of endometriosis need to be treated with caution because, although they are similar to what the disease is like in humans, they cannot be exactly the same. What you need for an accurate experiment is to test resveratrol’s effects in humans...

...which is exactly what the next study was looking at. This study comes from Brazil and was looking at 12 women with endometriosis who were taking the contraceptive pill as a treatment but failed to obtain any pain relief from their dysmenorrhoea and pelvic pain. What they did was give these women, in addition to their pill, a regime of 30mg a day of resveratrol for 2 months. They assessed the women’s pain by using a scoring system where a result of 3 indicated the highest amount of pain. At the beginning, where the women were only taking the pill, their average pain score was 2.1. Incredibly, after 2 months of the pill + resveratrol, their average pain scores had dropped to 0.2.

The authors of this study think that resveratrol acts as a natural aromatase inhibitor. Aromatase being an enzyme sometimes found in endometriotic cells, which basically can make them self sustaining and unresponsive to conventional treatments. So resveratrol in combination with the pill seems to have a very encouraging effect on dysmenorrhoea and pelvic pain, but this study only examined 12 women. In order to see if this result is correct this study needs to be replicated with a much larger group of women and possibly compare resveratrol to existing aromatase inhibiting drugs.

You may recall that at the beginning of this post I mentioned that resveratrol is found in many different types of fruit, so you can get it in your diet, but it’s also found in red wine. Aha! You may think, time to crack open a bottle of Spanish cabernet! 

"Its medicinal, honestly"    

 Image from Freedigitalphotos.net

Well before you reach for the bottle opener just be aware that, in order to get a 30mg dose of resveratrol, you would need to drink between 2 and 15 litres of red wine a day (depending on the wine), which I would definitely not recommend to anyone, ever. If you think you could get away with just eating red grapes, more bad news I’m afraid, as you would have to eat nearly 4Kg of red grapes a day to get the right dose. Even if you could somehow manage this Herculean task, resveratrol is not absorbed very well by the body so you may not see any benefits.

You can buy resveratrol supplements, however you should NEVER buy anything from an unlicensed pharmacy and, as a precaution, never buy anything off the internet. If you are curious about resveratrol supplements I would recommend talking to either your doctor or local pharmacist.

Nuking Endometriosis

Endometriosis is a notoriously difficult condition to treat; there are the drug therapies, but they are often hit or miss and can come with a plethora of unpleasant side effects. Then there is surgical treatment, which has the advantage of a better rate of relieving symptoms but it cannot guarantee the disease won’t return later, which may result in more surgery. Either way there always seems some medical or surgical options available, but what happens when the options run out?

A recent case report from Yamagata University Hospital in Japan starts with the authors finding themselves in that very situation. They were presented with a 47 year old woman with endometriosis (specifically chocolate cysts on both ovaries) who also experienced abnormal vaginal bleeding to the point where she was requiring blood transfusions. Medical therapy for her endometriosis didn’t help so the next logical step would be surgery, right? Not in this case, unfortunately the woman in question also suffered from idiopathic thrombocytopenic purpura (mercifully shortened to ITP) which means she has an abnormally low red blood cell count, making surgical intervention extremely dangerous.

Her doctors clearly weren’t in the giving up mood and in an inspired move decided maybe radiotherapy was the answer. You’ve probably heard of radiotherapy before but it’s normally used to treat tumours. In this case though the doctors elected to create a ‘radiation induced menopause’ by targeting the woman’s ovaries and endometrium with controlled doses of radiation. The authors report that after this course of radiotherapy the woman’s symptoms had abated and the abnormal vaginal bleeding had stopped.

Overall this was an extreme but successful treatment option for this patient. It’s not the first instance of radiotherapy for endometriosis either, but it is incredibly rare that this method is employed, mainly because it’s unusual for a patient to not respond to medical therapy and be unable to have surgical treatment. Also a major drawback is the irreversible loss of all ovarian function, so it would not be recommended for anyone who ever wants a family and hormone replacement therapy would probably be needed to control menopausal symptoms.