Interaction of M2 macrophages and endometrial cells induces downregulation of GRIM-19 in endometria of adenomyosis.

Research Question: Does the aggregation of M2 macrophages affect the expression of gene associated with retinoid-interferon-induced mortality 19 (GRIM-19) in adenomyosis?

Design: Endometrial tissues were collected from patients with (n = 15) and without (n = 15) adenomyosis. Tissues were analysed for GRIM-19 and toll-like receptor 4 (TLR4) expression by immunohistochemistry and western blotting. Apoptosis was analysed by TdT (terminal deoxynucleotidyl transferase)-mediated dUDP nick-end labelling (TUNEL) assay. Human endometrial stromal cells (HESC) were transfected with GRIM-19 small interfering RNA (SiRNA) to knockdown GRIM-19 expression. The HESC were co-cultured with M2 macrophages to detect the influence of M2 macrophages in HESC cells. Analyses included GRIM-19, caspase-3 and TLR4 expression by western blotting, and GRIM-19 and TLR4 by quantitative real-time polymerase chain reaction. Apoptosis was measured by flow cytometry and TUNEL assay. Cell proliferation (Cell Counting Kit-8 assay) and migration assays were carried out.

Results: The expression of GRIM-19 was significantly lower in adenomyosis lesions compared with controls (P < 0.001). Deficiency of GRIM-19 induced by siRNA decreased apoptosis and increased proliferation and migration in HESC. A significant decrease in GRIM-19 expression occurred in HESC after co-culture with M2 macrophages (P = 0.018). After co-culture with M2 macrophage, apoptosis decreased and proliferation and cell invasion in HESC increased. Protein (P = 0.006) and mRNA (P = 0.013) expression of TLR4 in HESC also reduced after this co-culture. Up-regulation of GRIM-19 occurred in HESC treated with the activator TLR4 (P = 0.016). Up-regulation of GRIM-19 was significantly reversed in cells treated with the TLR4 inhibitor (P = 0.011).

Conclusion: M2 macrophages may be involved in regulating the expression of GRIM-19 partly through the TLR4 signalling axis in adenomyosis.