Endometriosis, characterised by the presence of endometrial-like lesions outside of the uterus, is a debilitating and incurable gynaecological condition(1). Current diagnosis relies on invasive laparoscopic surgery(2). None of the proposed mechanisms thus far definitively explain the pathophysiology of the disease, nor have they been beneficial for non-surgical diagnostic methods(3). We aim to investigate menstrual fluid and its components as a non-invasive tool to better understand endometriosis and identify and utilise them as biomarkers for early diagnosis.
Menstrual blood was collected from women diagnosed with endometriosis (Endo,n=5) and healthy women (no symptoms of endometriosis, Ctrl,n=3) on day 2 of menses using a menstrual cup. Menstrual fluid supernatant was separated, and protein levels quantified. The abundance of 105 cytokines in menstrual fluid was assessed using multiplex array kits. Pixel density per cytokine signal was quantified, and statistical difference of the relative change in cytokine levels between groups was analysed using the two-tailed Mann-Whitney test with a confidence level of 99%.
Acrp30, C5/C5a, CHI3L1, IGFBP-3, IL-1β, MMP-9, OPN, PECAM-1, PF4, Serpin E1, SHBG, TFF3, THBS1, VCAM-1, VDB and VEGF were highly abundant in the menstrual fluid from both groups. Also present in lower abundance in both groups were interleukins (6,11,17A,18BPa and 19) and chemokines (CXCL9, CCL2, CCL20). These factors are associated with inflammation, decidualisation, tissue breakdown, blood loss regulation and tissue regeneration, supporting menstruation as a pro-inflammatory piecemeal event(4, 5). C-Reactive Protein (linked to infection), BAFF (B-cell activating factor), lipocalin-2 (released by neutrophils), IL-8 (a pro-inflammatory cytokine and chemokine for neutrophils), and angiogenin (pro-angiogenesis) were highly expressed in menstrual fluid from women with endometriosis compared to control groups, supporting the pro-inflammatory nature of endometriosis and the bacterial association of endometriosis(3, 6-9).
Menstrual fluid may serve as a minimally invasive diagnostic tool and provides valuable resources for biomarker identification for early diagnosis of endometriosis.