Long–Term Organ Culture Reveals Differential Stem Cell–Driven Remodelling in Myometrium and MED12–Mutant Uterine Leiomyoma

Uterine leiomyomas or fibroids are highly prevalent benign tumors of the female reproductive tract, often causing significant symptoms and requiring surgical intervention, leading to substantial healthcare costs worldwide. Their molecular pathogenesis remains incompletely understood, but evidence suggests that somatic stem cells play a pivotal role in myometrial growth, whereas a genetic alteration, particularly mutations in MED12, may transform a myometrial stem cell into a tumor-initiating cell, promoting fibroid growth. In organ cultures of fibroids and myometrium, most differentiated cells degenerated by day 7, whereas stem cells remained quiescent and viable within their native niches. Notably, between days 15 and 29, hypoxia–induced activation triggered stem cell proliferation and differentiation within the ex vivo slices. Transcriptomic profiling revealed statistically significant upregulation of stemness–associated genes, including HMGA, ITG, KLF, HOX, and SOX family members, in long–term cultured slices compared with baseline tissue, and between normal and tumor cultures. Reactome pathway enrichment analysis further identified distinct metabolic, extracellular matrix remodeling, immune surveillance, angiogenic, and cell death–related programs distinguishing myometrial from leiomyoma cultures. Furthermore, previously reported gene and pathway differences between healthy and fibroid tissues were robustly confirmed, validating the culture model. In conclusion, our findings establish long-term organ culture as a powerful, physiologically relevant platform for investigating stem cell dynamics in myometrium and uterine leiomyoma. They also provide proof of concept for extending this approach to other tissue types, enabling the discovery of mechanisms underlying stem cell activation, differentiation, and death, with broad translational potential in regenerative medicine and cancer biology.