Abstract
Endometriosis is a chronic inflammatory condition characterised by the presence of endometrium-like tissue outside the uterus. It is estimated to affect around 1 in 9 people of reproductive age assigned female at birth. Symptoms such as persistent pelvic pain, fatigue, and dysmenorrhea can substantially impact quality of life. Diagnosis currently relies on an invasive and time-intensive laparoscopic surgery that does not always provide confirmation of endometriosis. A deeper understanding of the pathophysiology of endometriosis could thus support the development of non-invasive methods of diagnosis.
Endometriosis is characterised by chronic inflammation, immune dysregulation, and endocrine alterations. Neutrophil extracellular traps (NETs) have been implicated in other inflammatory diseases, prompting interest in their role in endometriosis. This study employed a published flow cytometric panel for quantification of neutrophil-appendant NETs in peripheral blood to compare the NET burden in people with endometriosis to symptomatic and asymptomatic controls. We also compared in vitro NETosis in neutrophils from endometriosis patients and healthy controls treated with β-oestradiol or progesterone.
To examine the NET burden in people with endometriosis, symptomatic controls, and asymptomatic controls, neutrophils were isolated from peripheral blood collected from patients having laparoscopic surgery, or from healthy volunteers, and analysed with a published 6-marker flow cytometry panel designed for the detection of neutrophil-appendant NETs in peripheral blood. This component of the study demonstrated no statistically significant differences in NET burden between the three study groups. However, there was greater variation in NET burden within the endometriosis group and symptomatic control group compared to the asymptomatic control group – an aspect that warrants further investigation.
To compare in vitro NETosis between people with endometriosis and healthy controls, peripheral blood was stimulated with phorbol 12-myristate 13-acetate (PMA), a potent NET agonist, and treated with β-oestradiol or progesterone. This component of the study suggested that neutrophils isolated from people with endometriosis exhibited a dampened response to stimulation with PMA and to treatment with β-oestradiol and progesterone. However, this aspect of the study was statistically limited by its small sample size.
These findings demonstrate that NET burden may not be markedly different in people with endometriosis compared to controls. The variation in NET burden within the endometriosis group is possibly due to the heterogeneity of this disease. This warrants further stratification of a larger endometriosis group for subgroup analysis. The dampened response to stimulation and hormone treatment in neutrophils from people with endometriosis warrants further statistical analysis with an increased sample size.