Neuroinflammation in endometriosis: macrophages behaving badly?

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Endometriosis is an inflammatory condition, defined by the presence of womb lining (endometrium) outside the womb, most commonly on the lining of the wall of the pelvic cavity ('endometriosis lesions'). This is thought to occur via a phenomenon known as 'retrograde menstruation', where the endometrium that is shed during menstruation is refluxed backwards through the Fallopian tubes into the pelvic cavity. Endometriosis affects approx.1.5 million women in the UK and a large majority of women with endometriosis also have debilitating pelvic pain. Costs incurred by treating women with endometriosis and associated loss of productivity are estimated at £11.7 billion per year. Endometriosis is treated surgically or with drugs that suppress hormones, but symptoms usually recur after surgery and the available medical treatments have undesirable side effects. Women want new treatments to ease their suffering. Why endometriosis causes pain is poorly understood but I believe that it is due to the growth of new nerves into the lesions and their stimulation by molecules involved in inflammation (neuroinflammation). Notably, endometriosis can also be found associated with a general increased sensitivity to pain. Immune cells, such as macrophages are critical in the inflammatory process. Each tissue has its own 'type' of macrophage and they have been identified as important cells in the disease progression of endometriosis. We do not know how macrophages affect nerve growth in endometriosis or contribute to pain in the condition. However, I have recently shown that macrophages manipulated in the laboratory to mimic macrophages found in endometriosis lesions increase nerve growth and inflammation. I have developed a novel experimental mouse model of endometriosis that mirrors the human condition. The lesions form in a similar way to the human, and the mice also exhibit endometriosis-associated pain. Using this model I have shown that macrophages from the pelvic cavity migrate into lesions. Notably, for the first time I have also shown that macrophages present in the shed endometrium at the time of menstruation also survive in the lesions. This model will allow me to determine how macrophages contribute to neuroinflammation, endometriosis-associated pain and subsequent increases in sensitivity to pain. My specific aims are fourfold; firstly I will investigate how macrophages, that are present in the shed endometrium at the time menstruation, influence the formation of endometriosis lesions using a laboratory mouse model of 'menstruation' and endometriosis. Secondly, I will determine how macrophages influence nerve growth and neuroinflammation in endometriosis lesions. Thirdly, I will determine how factors produced by macrophages that have been identified in the previous objective, interact with nerves by using pain-sensing nerves grown in the laboratory. Finally, I will determine if macrophages play a role in endometriosis-associated pain and general increased sensitivity to pain, and to discover whether inhibition of factors produced by macrophages can reduce this pain.I have developed innovative new models and produced exciting and informative novel preliminary data and I am confident that I can deliver the specified aims. I believe that information generated during this fellowship will lead to quality high impact publications, new understanding of how endometriosis causes pain and will inform new ways to treat endometriosis-associated pain.