No abstract

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, leading to activation of Rho-dependent signaling. Here we sought to determine whether the altered ECM produced by leiomyoma was accompanied by an altered state of mechanical homeostasis.Study Design-Measurement of the mechanical response in paired leiomyoma and myometrium, immunogold, confocal microscopy, and immunohistochemical analyses.Results-Leiomyoma were significantly stiffer than matched myometrium. The increased stiffness was associated with a moderate increase in total sulfated glycosaminoglycan content and a slight increase in hydroxyproline. Levels of the Rho-GEF, AKAP13, were increased and subcellular localization was altered in leiomyoma. Phosphorylation of p38MAPK was greater in leiomyoma extracts. Conclusions-Leiomyoma

Uterine leiomyoma are common, benign tumors that are enriched in extracellular matrix. The tumors are characterized by a disoriented and loosely packed collagen fibril structure similar to other diseases with disrupted Transforming growth factor β (TGF-β) signaling. Here we characterized TGF-β3 signaling and the expression patterns of the critical extracellular matrix component versican in leiomyoma and myometrial tissue and cell culture. We also demonstrate the regulation of the versican variants by TGF-β3. Using leiomyoma and matched myometrium from 15 patients, messenger RNA (mRNA) from leiomyoma and myometrium was analyzed by semiquantitative real time reverse transcription–polymerase chain reaction (RT-PCR), while protein analysis was done by western blot. Transforming growth factor β3 transcripts were increased 4-fold in leiomyoma versus matched myometrium. Phosphorylated-TGF-β RII and phosphorylated-Smad 2/3 complex were greater in leiomyoma as documented by Western blot. The inhibitor Smad7 transcripts were decreased 0.44-fold. The glycosaminoglycan (GAG)-rich versican variants were elevated in leiomyoma versus myometrial tissue: specifically V0 (4.27 ± 1.12) and V1 (2.01 ± 0.27). Treatment of leiomyoma and myometrial cells with TGF-β3 increased GAG-rich versican variant expression 7 to 12 fold. Neutralizing TGF-β3 antibody decreased the expression of the GAG-rich versican variants 2 to 8 fold in leiomyoma cells. Taken together, the aberrant production of excessive and disorganized extracellular matrix that defines the leiomyoma phenotype involves the activation of the TGF-β signaling pathway and excessive production of GAG-rich versican variants.