Endometriosis is a complex, chronic condition characterised by growth of benign endometrial-like lesions outside the uterine cavity. Despite research, the origins and pathogenesis of endometriosis remain poorly understood. Mass Spectrometry Imaging (MSI) is a technique that permits spatial biomolecule identification within tissue sections. Utilising MSI, we aim to investigate endometriotic lesions, uncovering disease mechanisms and potential diagnostic biomarkers.
We optimised published MSI methods for analysing ‘omic profiles (proteomic and glycomic) of endometrium and lesions using formalin-fixed paraffin-embedded (FFPE) samples. Digestive enzymes (trypsin/PNGaseF) and MALDI matrices (cyano-4-hydroxycinnamic acid, 2,5-dihydroxybenzoic acid, 9-aminoacridine) were employed for preparation. We then assessed ‘omic MSI data from endometriosis tissues and a healthy endometrial tissue microarray. Tissue were analysed using a Bruker SolariX 2XR MALDI-FT-ICR MS system, processed using SCiLS Lab 2024, receiver operating characteristic curves and linear discriminant analysis.
Preliminary data suggests that protein peptides and N-glycans are capable of discriminating between lesion and non-lesion tissues. Fifteen peptides distinguished endometrial cycle phases on the microarray, elevated during the secretory phase. Eight peptides within endometriotic lesions (present in 66.67% of lesions) hold promise as potential biomarkers upon further validation.
Our N-glycome research identified 15 differential N-glycans across endometrial cycle phases, with increased levels during the secretory phase. This increase compared to proliferative phase was mimicked in endometriotic lesions. We detected 16 N-glycan peaks predominantly in lesions, some exclusive to lesion sites. Classification models using significant peptides and N-glycans showed success in a small sample cohort, suggesting future validation with a larger cohort.
These findings hint at a potential similarity between endometriotic lesions and endometrial profiles measured during the secretory phase, warranting further analysis. While further investigation of identified peptides and N-glycans are needed, combined with annotation and validation using orthogonal tandem mass spectrometry (currently underway), they hold promise of becoming tools in understanding endometriosis.