BMAL1 knockdown impairs integrin-mediated adhesion and migration in endometrial cells, reducing embryo implantation.

Successful embryo implantation is a complex, tightly regulated process crucial for human reproduction, yet the precise molecular mechanisms governing endometrial receptivity remain incompletely understood. Current understanding highlights the importance of endometrial changes, including the expression of adhesion molecules like integrins, during the 'window of implantation'. Disruptions in this process contribute to recurrent implantation failure. Circadian rhythm regulators, particularly brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (BMAL1), are emerging as key modulators in reproductive biology, offering a novel pathway to investigate this critical gap.

Researchers investigated BMAL1's role in endometrial receptivity using Ishikawa cells, a human endometrial adenocarcinoma cell line. Cells were transfected with BMAL1-specific siRNA or control siRNA to achieve knockdown. Molecular analyses included RT-qPCR, western blotting, and immunofluorescence to assess gene and protein expression. Functional assays comprised migration assays to evaluate cellular motility, and co-culture with JEG-3 spheroids (a choriocarcinoma cell line mimicking an embryo) to directly measure embryo adhesion. Cell viability and cytotoxicity were also assessed to ensure specific effects.

BMAL1-knockdown in Ishikawa cells significantly altered adhesion-related gene expression and cellular function. Specifically, BMAL1-knockdown downregulated adhesion-related genes, including ITGAV, ITGB3, and ITGB5. While total ITGB5 protein levels remained stable, its localized expression intensity was significantly reduced. Furthermore, protein expression of ITGAV and ITGB3 was decreased, and cell migration was impaired. Notably, BMAL1-knockdown compromised cellular motility without significantly affecting cell viability or cytotoxicity, indicating a specific effect on adhesion and migration pathways. > A co-culture model with JEG-3 spheroids demonstrated significantly decreased embryo adhesion following BMAL1-knockdown, directly linking BMAL1 to successful implantation.