Loss of sympathetic nerve fibers in intestinal endometriosis.

Bowel endometriosis affects 4–37% of women with endometriosis. Deep intestinal nodules may determine pain and a variety of intestinal symptoms, which sometimes mimic irritable bowel syndrome and Crohn disease. A previous study showed that specialized myofibroblast cells, named interstitial cells of Cajal, are damaged in women with bowel endometriosis. However, the mechanisms by which endometriosis affects gastrointestinal function are largely unknown. Nerve fibers and their respective neurotransmitters contribute to intestinal inflammation. The wall of the human gut is richly innervated by sympathetic nerve fibers and by sensory fibers expressing the neuropeptide substance P (SP). Immune cells express adrenergic receptors; catecholamines at low concentrations bind to a-adrenoceptors and lead to cyclic adenosine monophosphate (cAMP) decrease and production of proinflammatory cytokines, whereas catecholamines at high concentrations bind to Beta-adrenoceptors and lead to cAMP increase and antiinflammatory effects. This study analyzed by immunofluorescence staining the sympathetic innervation in the bowel adjacent to the endometriotic lesion and in the healthy tissue at the border of the resected specimen. Sympathetic nerve fibers are significantly reduced in the mucosal and muscular layer near the endometriotic lesions; in contrast, sensory nerve fiber density is not altered in the area near the endometriotic lesions.