P-316 Involvement of collective cell migration in endometrial invasiveness in uterine adenomyosis and the role of M2 macrophages
Authors: Stratopoulou C A , Donnez J , Dolmans M M 
Published: June 2023

Abstract

Study question
How do endometrial cells manage to invade surrounding myometrium to establish adenomyotic lesions and what is the role of macrophages in this process?

Summary answer
M2 macrophage-mediated invasiveness and resistance of endometrial cells to physiological cell death appear to contribute to the pathogenesis of adenomyosis.

What is known already
Despite the high prevalence and debilitating symptoms of uterine adenomyosis, its pathogenesis has not yet been elucidated. To date, the most acceptable theory to explain disease development suggests invasion of the myometrium by eutopic endometrial cells.
Recent data suggest aberrant infiltration of immune cells but not platelets in adenomyosis, eventually leading to enhanced cell motility via collective cell migration (CCM) and resistance to physiological cell death during disease pathogenesis.

Study design, size, duration
A retrospective immunohistochemistry-based study was conducted on formalin-fixed paraffin-embedded uterine tissue from 17 women (8 adenomyosis patients and 9 healthy subjects). Fresh endometrial biopsies were retrieved from 16 women (6 adenomyosis patients and 10 healthy subjects) for in vitro culture of epithelial and stromal cells, and co-culture with THP-1 monocyte-derived M2 macrophages.

Participants/materials, setting, methods
Double immunofluorescence was performed to detect macrophages of M1 and M2 phenotypes. Invasiveness of endometrial cells upon interaction with macrophages was assessed by in vitro invasion assays and quantitative PCR for genes involved in cell motility and epithelial-mesenchymal transition (EMT). Mechanisms of disease progression were investigated by immunohistochemistry against E-cadherin, N-cadherin and matrix metalloproteinase 9 (MMP9). Caspase 3 and microtubule-associated protein light chain 3 beta (LC3B) were studied as markers of apoptosis and autophagy respectively.

Main results and the role of chance
Only M2 macrophages were found to accumulate in adenomyosis, in higher numbers in both endometrium and ectopic lesions from adenomyosis patients than healthy controls. Co-culture with M2 macrophages significantly increased invasion capacity in endometrial epithelial and stromal cells from both adenomyosis patients and healthy controls. Epithelial cells from adenomyosis patients were nonetheless more invasive than their healthy counterparts in the presence of M2 macrophages. No gene expression differences pointing to EMT were noted, either between co-cultured and control cells, or between adenomyotic and healthy cells, refuting the implication of this mechanism in adenomyosis invasiveness. E- and N-cadherin protein expression did not differ significantly between eutopic endometrium from adenomyosis subjects and healthy tissue, but N-cadherin expression was stronger in ectopic lesions. In adenomyosis, both E- and N-cadherin were more extensively expressed in basal (also known as invasive) glands than functional glands, suggesting maintenance of intercellular junctions and subsequent CCM. Extracellular matrix-degrading enzyme MMP9 was more abundantly expressed in eutopic stroma from adenomyosis patients compared to healthy tissue. Lower levels of caspase 3 were detected in both endometrium and lesions from adenomyosis patients, while LC3B was found significantly decreased in adenomyotic stroma compared to that of healthy subjects.

Limitations, reasons for caution
A limitation of the study is the 2D nature of in vitro cultures, which cannot fully reconstitute in vivo cell arrangement and cell-cell interactions, nor allow to observe CCM in real time.

Wider implications of the findings
M2 macrophages accumulating in endometrium and ectopic lesions from adenomyosis patients boost invasion capacity of endometrial epithelial and stromal cells, as shown by in vitro co-culture experiments. These findings indicate that M2 macrophages play a key role in disease pathogenesis and could be targeted to develop novel therapeutic options.

Trial registration number
not applicable