Mechanical homeostasis is altered in uterine leiomyoma

Objective: Uterine leiomyoma produce an extracellular matrix (ECM) that is abnormal in its volume, content, and structure. Alterations in ECM can modify mechanical stress on cells and lead to activation of Rho-dependent signaling and cell growth. Here we sought to determine whether the altered ECM that is produced by leiomyoma was accompanied by an altered state of mechanical homeostasis. Study Design: We measured the mechanical response of paired leiomyoma and myometrial samples and performed immunogold, confocal microscopy, and immunohistochemical analyses. Results: Leiomyoma were significantly stiffer than matched myometrium. The increased stiffness was accompanied by alteration of the ECM, cell shape, and cytoskeleton in leiomyoma, compared with myometrial samples from the same uterus. Levels of AKAP13, a protein that is known to activate Rho, were increased in leiomyoma compared to myometrium. AKAP13 was associated with cytoskeletal filaments of immortalized leiomyoma cells. Conclusion: Leiomyoma cells are exposed to increased mechanical loading and show structural and biochemical features that are consistent with the activation of solid-state signaling.