Hugh Taylor, MD - Depression in endometriosis

Thank you. First, I'd like to start by thanking Dr. Seckin for organizing such a wonderful conference, bringing us all together to learn more about endometriosis, share the latest, and really help us fight this terrible disease. I'm going to talk to you about depression and endometriosis. I love the theme of this year's meeting, nerves and endometriosis, but the one big nerve is the central nervous system, and there are many defects in the central nervous system, including depression that are more common in endometriosis. And I think we have to remember that we're not just treating the lesions, we're treating the whole patient. That endometriosis is a disease with lots of manifestations beyond the lesions, and depression's a major complication of endometriosis. So I'll tell you a little bit about the work we've done in this area. I've spent the last decade or so looking at how endometriosis has effects on other organs, considering a systemic disease with multiorgan effects.

And I'll show you today that the brain is an organ that is affected by endometriosis and some of what the mechanisms are that mediate that. But first, I think there all know the association between endometriosis and mental health. It's strongly associated with multiple mental health disorders, but particularly depression and anxiety. And large population-based studies and cohort studies indicate that there's a significant increase in both the depression and anxiety and women with endometriosis. The systemic reviews and looking at databases of estimated ranges from 10 to 30% among patients, but a lot of this is influenced by study design. I mean, we know endometriosis isn't always diagnosed. It's not always in the medical record. How do you make these correlations? We know there's a tremendous delay in diagnosis. Same is true sometimes for depression. When your main complaint is pain, you may get that in depression neglected.

And often they're cared for in different areas. A patient may see an outpatient psychiatrist and go to the hospital for their endometriosis surgery. So they're not always linked together there. But we know it's higher in patients who experience pain and the stress of infertility also increases depression. I think more accurate representation of the true incidents of depression in endometriosis. So some of the surveys where you ask a woman with endometriosis, has she had depression? About half say they've had clinical diagnosed depression. It is very, very common. And I think when we look at the literature, it's probably tremendously underestimated. I'll show you something anyways. This is a large retrospective cohort study in the US. 72,000 women. They found rather 47 per thousand, about 5%. I think it's a tremendous underestimate. But a hazard ratio compared to those without endometriosis about 1.5. So one and a half times 50% higher risk roughly.

This is a very recent study just done last year. Again, about the same relative risk, 1.5 in women with endometriosis of having depression. Again, I would suggest to you this is an underestimate, but it's not just everybody with endometriosis. The more severe your symptoms are, the more likely you are to have depression. If you have chronic pain with your endometriosis, you have about a fourfold risk of having depression. And if you have dyschesia, you have about an eightfold risk almost of having depression. So it correlates with the amount of symptomatology. There are lots of mechanisms linked to this. I mean, pain itself may cause the dysmenorrhea dyspareunia exacerbates stress and depressive symptoms. There is inflammation, as we all know, that occurs with endometriosis, and that systemic inflammation produces certain neuroendocrine changes that may influence mood. We'll come back to that later. There's also a genetic susceptibility, and I'll show you some of the work that we've done recently on that to show that there is a genetic correlation between endometriosis and depression, suggesting there are some shared horrible risks, common genes that might actually influence both.

And of course, infertility and other stressors increase the risk of depression. So this is a figure from a paper that's now under review that was actually done by the first author there. First name's Anna. She's here in the audience and a student I'm co-mentoring with Dr. Abrau, our last speaker, and she's looking at depression, endometriosis. And she points out some of the main mechanisms here, biological, the endometriosis, pain and inflammation actually influencing the brain, the psychological and the social impacts that may lead to depression. First, let's talk about that genetic predisposition. This is a work we did with Dora Kohler. She's in the psychiatry department at Yale and did a genetic association study looking at 8,000 women with endometriosis and almost 200,000 controls, and found that genetic pleotropy is likely associated with comorbid depression, anxiety, and eating disorders in endometriosis. This used the UK Biobank, and I won't go through all the details here, but basically looked at the genome-wide association and the incidents of these conditions, depression, anxiety, and eating disorders in endometriosis.

And this is what we found, increased or rather a correlation with genetic risk and depression with anxiety and eating disorders. The eating disorders had the highest risk, but the confidence intervals very wide. And as you'll see on this next slide, actually, it wasn't statistically significant, even though it was higher because again, a lot of variability there. But depression had a very high P value, very closely linked to an endometriosis, depression, and endometriosis to common genetic variables. So there is a genetic predisposition to developing both endometriosis and depression.

Also with Doricohler in the psychiatry department, we looked at stress, either childhood or adult, traumatic experience and stressful events and their effect on endometriosis. And I also looked to see if there could be a genetic predisposition to those. In particular, the findings highlighted the potential association between contact trauma, meaning physical abuse, sexual abuse, and endometriosis, which did not correlate with that genetic predisposition. So again, I won't go through this in detail, but I think it's well known that multiple traumatic experiences can predispose to endometriosis, whether that is as a child or even abuse or trauma or traumatic experiences as an adult.

Then I'd like to point out is that sometimes we make depression worse. Is there an iatrogenic component to endometriosis? Oral contraceptives are our first line treatment for endometriosis. This is a study done by one of the trainees in my lab who recently left Jensu, and she looked at a big database, about 2000 OC users and about almost 700 non-users, and just looked to see in endometriosis, if you started an oral contraceptive, did you develop depression? And you can see there in our study, the non-OC users had about a 20% incidence that went up to almost 40% in those when we started them on an oral contraceptive. Women with endometriosis are much more sensitive to depression as a side effect of oral contraceptive use than the general population. We have to be careful not to iatrogenically induce depression in our patients with endometriosis.

But as I mentioned before, I've spent maybe the last 10 years looking at how endometriosis impacts other organ systems remote from the pelvis. And endometriosis we've shown affects multiple different organs and some of that is through inflammation, including neuroinflammation in the brain. Some of it is through cell trafficking. Some of it is mediated through circulating microRNAs, which is what I'm going to focus on here today. In particular, several microRNAs that are changed in the circulation of women with endometriosis and impact the brain. So we'll talk about the biologic basis of endometriosis and how it affects the brain and depression. This is a paper we did, oh, it's several years ago now, where we create endometriosis in mice. And in this model, these mice aren't experiencing any discernible pain. Yet when we took out their brains and looked at them, there were changes in gene expression in the brain shown here on the left and lots of different genes had differential expression.

We looked in the brains, that's the amygdala and the insula. We saw several different genes that were differentially expressed in these brains that are often associated with depression. So there's a change in the brain of mice when we give them endometriosis, proving cause and effect. We looked at the electrophysiology and there were some subtle differences in the electrical conductivity of the brain. The brain is wired differently in endometriosis or in response to us creating endometriosis, it is causal.

And most importantly, these changes in the brain led to depression. Now in a mouse, the standard accepted test for depression is holding that mouse up by its tail and a normal mouse will struggle to get away pretty quickly. A depressed mouse will lay there listless for a while and doesn't struggle to get away right away, what we call the immobility time. And you can see in the endometriosis, the black bar is there. By four weeks, we saw a significant increase in that immobility time. These mice were more depressed after we created endometriosis within four weeks. Pretty rapidly, these changes occur. Changes in gene expression, changes in electrophysiology of the brain that lead to depression. And that persisted after we experimented on our mice, they caught them all the time and their depression rose a little bit over time, but the endometriosis group was always higher and had more depression.

I want to show you some of the work we're trying to get at exactly what's mediating that now. And this work, I'll show you some of our new single cell sequencing data that the first author of this work is Namesha, who's also here with us in the audience, who's one of our other trainees working with me, who's done a lot of great work really understanding what is responsible for these changes in the brain. She's just about got this ready for publication. She did some whole brain single cell seq. And I want to point out in comparing endo versus non-endo, and I want to point out the microglia, these inflammatory cells of the brain are really pretty pronounced here. And this was just the microglial cluster magnified. I'm going to just summarize some of the gene expression changes she saw. This was looking at the gene expression in the microglia, comparing endometriosis to non-endometriosis.

And again, differences in microglial gene expression. These are really the inflammatory mediating cells of the brain, very different. Here's just a summary of the top 15 genes differentially expressed in endo versus non-endo in those microglia. A large proportion or a large portion of these effects we think are mediated through these inflammatory cells in the brain. The other thing we saw, again, we show that first graph there looks at that immobility time. It's increased when we created endometriosis in this model as well. The other thing we saw is that the hippocampus is smaller. This is something that is known in women with depression. Their hippocampus is smaller. From MRI studies, we know it gets smaller. In our animal model, the hippocampus gets smaller and shrinks. So there's effect on hippocampus, and I'd like to suggest mostly microglial cells as well in the hippocampus. Here's some genes that are downregulated in the hippocampus, all nemesis work, of course.

You can see that several genes are downregulated that are involved in neurogenesis and associated with depression. So big changes in response to that endometriosis. And part of what mediates this is microRNAs, as I'll show you in a minute. But for those of you not familiar with microRNAs, these are small RNA molecules genome. They're transcribed into RNA, but they're not translated into proteins. They're heavily processed and they turn out to be these small 20 nucleotide or so length MRIs that tend to bind messenger RNA and turn off gene expression or lead to degradation of these RNAs. So they generally block gene expression. We know they're not only just made in endometriosis, but they're also secreted out of the cells where they're made, entered the circulation, and can have a hormone-like effect. They can have the same impact on cells very far removed from where they're made.

Well, several years ago, we showed that there are lots of micro RNAs in the serum of women with endometriosis that are very different in abundance compared to women without endometriosis. And several years ago, we even suggested this might be a diagnostic biomarker for endometriosis, but that's not what I'm here to talk to you about today. Several of those that are associated in particular with endometriosis have been previously associated with depression in the brain. MicroRNA-125, which is one of the prominent increase in the circulation of women with endometriosis has been associated with bipolar and Alzheimer's disease, microRNA-451, again, very high in women with endometriosis, has been associated with major depression. LET-7, which is decreased in endometriosis, has also been seen in treatment-resistant depression in the brain. So these same microRNAs that are altered in the circulation of women with endometriosis are known to impact the brain.

Well, are they doing that here? Are these microRNAs that are different in the circulation of endometriosis? Are they getting to the brain and really having these effects? Can we block them and prove that they're what's mediating this effect or at least part of that role? So Nemesha conducted these studies. This is the timeline here. We created endometriosis. We let it establish for a while to have its effect on the brain about six weeks. And then she treated these mice with either inhibitors of microRNAs that are increased or mimics that increased that microRNA expression of the LET7, which is decreased in endometriosis, then conducted some of those behavioral studies and then looked at the brains. So we can prove that these microRNAs really do or do not impact the brain and mediate the effect of endometriosis on depression. And this is what she showed. There's the immobility time.

Remember, it's increased showing depression in mice with endometriosis. All three of these microRNA treatments that we selected as most likely to be the ones that impact the brain, showed a decrease in this immobility time. They reversed that depression, not quite back down to completely normal, but significantly. Each one independently did this.

They also, at least two of them, restored the hippocampal volume. Remember I mentioned to you that hippocampal volume is decreased in our model. It's decreased in women with depression. Here in our model, we show that by treating with two out of those three microRNAs, we could restore hippocampal volume. And actually the third, there was a trend not quite significant. Maybe the few more, maybe it's a power issue, a few more, we may see that actually become significant, but eliminating the depression or at least reversing the depression, restoring the hippocampal volume. And I'll talk to you about one gene that we think has a major role in this, and that's the growth of rest and DNA and damage inducible 45 beta gene. It's a member of a gene family that is well known to be associated with cell growth apoptosis in the central nervous system. It is involved in DNA methylation and critical for regulating, already known to be critical for regulating adult hippocampal neurogenesis, and has an effect on those inflammatory cytokine production that I talked to you about.

If you knock it down in animals, others have shown you get depression. So clearly it mediates depression, and it's actually reverses quickly if you use electroconvulsive shock therapy to treat depression. Well, again, this is Nemesha's work. What she showed is it is indeed downregulated in endometriosis. You can see there, the protein level, it's decreased in endometriosis. And when we treat the mice with these micro RNAs, it shown on the far left there is that GADD45 beta, it is increased. It goes back up with micronA125, 451, or LET 7B treatment. Not all genes respond in this way. You can see many others there that are involved in it in the brain are not, but this one in particular is. So we think microRNAs are mediating this response. MicroRNAs in the circulation of women with endometriosis caused by these lesions, travel to the brain, influence gene expression of the brain, reversing the depression, reversing that hippocampal loss.

Again, this is just the protein level showing essentially the same thing. So I'll conclude by saying that microRNAs are potentially a novel therapeutic agent for endometriosis associated depression. Not only do we know the mechanism by which endometriosis, at least one of the mechanisms by which endometriosis causes depression, but maybe no understanding these mechanisms gives us some new targets and potential treatments. So I'll summarize the, again, endometriosis, as we all know, is associated with depression. They're genetic, biological, social, behavioral, and even iatrogenic causes of depression and endometriosis. Be careful with those oral contraceptives. Endometriosis induces depression in our mouse model, and the mechanisms of endometriosis induced depression include not limited only to shrinking that hippocampus and alterations in hippocampal gene expression, particularly in the microglia there, those inflammatory cells of the brain, and micro RNAs mediate some of these effects of endometriosis on the brain and treatment with endometriosis associated microRNAs, reduce depression, restore that hippocampal area, and normalize that gene expression of the brain.

So I think we know the mechanism by which endometriosis influences brain that leads to depression and have a potential therapy to help reduce depression in patients with endometriosis. Just want to acknowledge all the people in my laboratory who did this work. This is from one of our last Halloween party. They all dressed up as mice with their little ear tags with their numbers on them and the pink endometriosis lesions that we suture into the peritoneal cavity of the mice. The third one from the left is Anna, who I showed you her beautiful figure there who's here in the audience, and right in the center who did most of the brain work that I showed you was Nemesha. So want to thank them for all their hard work. Thank you.