Stage-dependent sphingosine-1-phosphate pathway modulation as a therapeutic strategy in a murine model of adenomyosis.

Adenomyosis is characterized by chronic inflammation, myometrial remodeling, and subfertility, yet therapeutic options that preserve reproductive potential remain limited. Sphingosine-1-phosphate (S1P) signaling regulates immune-cell trafficking, vascular remodeling, and tissue invasion, but its contribution to adenomyosis remains poorly defined. This study investigated the temporal regulation of this pathway in a tamoxifen-induced murine model of adenomyosis and evaluated whether its pharmacological inhibition alters uterine immune profiles and lesion severity. A total of 122 female CD1 mice were used (79 adenomyosis, 43 control). Preventive treatment (with FTY720) started at weaning, while therapeutic interventions (with FTY720 and SKI-5C) were initiated at 6 weeks. Outcomes included body/uterine weight, lesion prevalence, grading and depth, immune-cell phenotyping by flow cytometry, and uterine expression of inflammatory, angiogenic, and invasion-associated genes. Early disease (at 4 weeks) was marked by increased expression of S1PR1/2 and downregulation of SGPL, while established disease (at 12 weeks) showed that S1PR1 remained elevated with additional upregulation of SPHK1 and S1PR4. Preventive FTY720 reduced lesion depth and grade, whereas therapeutic SKI-5C decreased lesion prevalence and invasion. Uterine weight remained reduced across adenomyosis groups and was not restored by treatment. Immune profiling revealed no major differences in total T-cell abundance between the control and adenomyosis groups. However, SKI-5C treatment was associated with the most pronounced modulation of uterine immune cells, particularly affecting T- and NK-cell-related subsets. Gene expression analyses demonstrated increased interleukin-6 in early disease and modulation of urokinase-type plasminogen activator associated with the treatments. Study limitations included constraints related to immune-cell recovery from uterine tissue, the relatively short duration of treatment, and translational differences between murine and human adenomyosis. Overall, these findings indicate that S1P signaling contributes to immune microenvironment remodeling and lesion progression in adenomyosis. These results support S1P pathway modulation as a promising therapeutic strategy meriting evaluation in human studies.