Dr. Krina Zondervan
“It’s one thing identifying risk variants and the next question is, okay, well, what do those variants actually do in terms of biology?” Dr. Zondervan said. The Oxford team next explored how the identified genetic variants affect gene expression and the proteins generated, drawing on previously collected data on gene expression from samples of human blood and endometrial and uterine tissue.
They found many of the genes implicated in the risk for endometriosis code for proteins that affect sex hormones, uterine development, transformation of healthy cells into cancerous tissue, inflammatory adhesion molecules, and factors promoting development of new blood vessels. All of that, she said, explains how a few endometrial cells making their way into the pelvis can attach to ovaries, ligaments, and peritoneal surfaces; proliferate; and acquire a blood supply to ensure their survival.
“We were able to identify a whole host of things that were likely causal to the disease,” Dr. Zondervan said. And that finding led to her next question: “Are there particular genes or areas around them that can be targeted with certain medications?”
The surprising answer was that several of the genes linked to endometriosis share pathways with clinical syndromes that often occur in women with endometriosis. Many of these are chronic pain conditions – such as migraines, headaches, and back pain – but also include inflammatory illnesses such as asthma and osteoarthritis.
As Dr. Zondervan explained, “A lot of the variance that we see for endometriosis is also experienced for low back pain and migraine, and that clearly has something to do with pain perception and pain mechanisms.”
A connection between the development of neural pathways and endometriosis has been proposed before, as researchers have found that endometriotic lesions can develop their own nerve supply, creating a direct interaction between the lesions and the central nervous system. And some clinicians have been employing treatment strategies that employ multimodal therapies – employing physical therapists, mental health practitioners, nutritionists, and pain specialists prior to and following surgical removal of lesions – to improve overall success rates of treatment.
But Dr. Zondervan’s team is the first to uncover an important clue about how this happens.
The study findings also provide solid clues to researchers about which genes and proteins to focus on for drug target discovery. In particular, the gene pathways shared by endometriosis and various pain conditions could allow for repurposing of drugs developed for other conditions for treating endometriosis, reported Dr. Zondervan.
Dr. Zondervan’s other important conclusion, echoed by Dr. Kondo and Dr. Kommagani, is that endometriosis is not one disease. Rather, it appears to be akin to cancer in terms of the heterogeneity of how it presents and the different subtypes of diseases. The Oxford study corroborated this belief, identifying certain genes that were closely associated with cystic lesions in ovaries, but failing to turn up a genetic link to other types of lesions in the pelvis long considered to be part of the spectrum of endometriosis disease.
Dr. Zondervan agreed that the potential link with Fusobacterium is a fascinating area given the critical role of inflammation in the pathogenesis of endometriosis, although she’d like to see the work replicated with larger sample sizes. “From a personal point of view, I’d be really fascinated to see how genetics interplays with this,” she added.