Hormone-dependent protection against oxidative stress in uterine leiomyoma

Context. Uterine leiomyomas exist in a chronically pro-oxidant environment characterized by reduced antioxidant capacity, yet they persist and grow, suggesting the activation of adaptive stress-tolerance mechanisms. Although estrogen and progesterone are central drivers of leiomyoma growth, their role in regulating mitochondrial function under oxidative stress remains incompletely understood. Objective. To investigate how estrogen and progesterone signaling modulate oxidative stress–induced transcriptional programs and mitochondrial metabolic function in uterine leiomyoma cells. Design. Primary patient-derived leiomyoma spheroids were exposed to paraquat-induced oxidative stress in the presence of estradiol, progestins, or hormone receptor antagonists. Transcriptomic responses were assessed by RNA sequencing followed by differential expression and gene set enrichment analyses. Functional mitochondrial metabolism was evaluated using Seahorse extracellular flux assays, and cellular outcomes including senescence and cell death were quantified. Patients. Uterine leiomyoma tissues were obtained from patients undergoing hysterectomy, and primary patient-derived leiomyoma cells were used to generate three-dimensional spheroid cultures. Results. Estradiol and progesterone modulated oxidative stress–responsive transcriptional programs associated with senescence, apoptosis, and mitochondrial regulation. Hormone receptor antagonism induced the most pronounced transcriptomic disruption and was associated with increased senescence and cell death. Consistent with these findings, Seahorse analyses demonstrated that hormonal signaling preserved mitochondrial maximal respiration and spare respiratory capacity under oxidative stress, whereas hormone blockade impaired mitochondrial reserve capacity without compensatory glycolytic upregulation. Progesterone receptor isoform–specific effects further supported a role for differential PR signaling in regulating mitochondrial adaptability. Conclusions. Estrogen and progesterone promote mitochondrial adaptability in leiomyoma cells, enabling survival under sustained oxidative stress. These findings identify mitochondria as a key mediator of hormone-dependent stress resilience and highlight mitochondrial metabolism as a potential therapeutic vulnerability in leiomyomas.