Characterization of tissue biomechanics and mechanical signaling in uterine leiomyoma

Abstract

Leiomyoma are common tumors arising within the uterus that feature excessive deposition of a stiff, disordered extracellular matrix (ECM). Mechanical stress is a critical determinant of excessive ECM deposition and increased mechanical stress has been shown to be involved in tumorigenesis. Here we tested the viscoelastic properties of leiomyoma and characterized dynamic and static mechanical signaling in leiomyoma cells using three approaches, including measurement of active RhoA. We found that the peak strain and pseudo-dynamic modulus of leiomyoma tissue was significantly increased relative to matched myometrium. In addition, leiomyoma cells demonstrated an attenuated response to applied cyclic uniaxial strain and to variation in substrate stiffness, relative to myometrial cells. However, on a flexible pronectin-coated silicone substrate, basal levels and lysophosphatidic acid-stimulated levels of activated RhoA were similar between leiomyoma and myometrial cells. In contrast, leiomyoma cells plated on a rigid polystyrene substrate had elevated levels of active RhoA, compared to myometrial cells. The results indicate that viscoelastic properties of the ECM of leiomyoma contribute significantly to the tumor’s inherent stiffness and that leiomyoma cells have an attenuated sensitivity to mechanical cues. The findings suggest there may be a fundamental alteration in the communication between the external mechanical environment (extracellular forces) and reorganization of the actin cytoskeleton mediated by RhoA in leiomyoma cells. Additional research will be needed to elucidate the mechanism(s) responsible for the attenuated mechanical signaling in leiomyoma cells.

Two-dimensional gel electrophoresis analysis of the leiomyoma interstitial fluid reveals altered protein expression with a possible involvement in pathogenesis

“…Desmin is a type III intermediate filament expressed by skeletal, smooth, and cardiac muscle tissue (25). The leiomyoma is composed by an abnormal ECM (11). Thus, cells, exposed to different viscoelastic forces, continue to grow and proliferate (26).…”

“…Abnormal extracellular matrix (ECM) protein expression, and increased growth factors, cytokines and chemokines leading to disorganized ECM are involved in the development and growth of uterine leiomyomas (10). Modifications of the ECM, its viscosity and elasticity, may change the intercellular communication by determining an increased mitotic activity (11). Mechanical signals are transmitted by the receptor from the ECM to the cytoskeleton, in order to maintain an isometric state and structural organization of a default (12 GTPase protein, appears to be part of a mechano-regulatory circuit that could modify the interactions between proteins of the cytoskeleton by inducing leiomyoma growth (13).…”

Signaling Pathways in Leiomyoma: Understanding Pathobiology and Implications for Therapy

“…On the contrary, there is strong evidence that the ECM directly stimulates intercellular signaling. Because of the abnormal composition, structure, fluid content and stiffness of the tumor, there is increased tissue tension (153). This increased tissue tension and stretch induces mechanical signaling transmitted from collagen and other fibers in the ECM to intracellular components through transmembrane receptors including integrins and cadherins (153,154).…”

“…Because of the abnormal composition, structure, fluid content and stiffness of the tumor, there is increased tissue tension (153). This increased tissue tension and stretch induces mechanical signaling transmitted from collagen and other fibers in the ECM to intracellular components through transmembrane receptors including integrins and cadherins (153,154). This complex mechanical signaling network involves alterations in cell shape and cytoskeleton in addition to altered stiffness and ECM (155).…”

Identification of proteins with different abundance associated with cell migration and proliferation in leiomyoma interstitial fluid by proteomics

“…Several studies have shown that tumor growth is not only regulated by the malignancy of the tumor cells, but is also associated with several factors that are present in the tumor microenvironment, including cytokines, electrolytes and other secreted proteins (8). The IF flow movement may influence the degree of viscosity and elasticity of the ECM, thus modifying the intercellular communication and determining an increased mitotic activity (9). Collagen and other proteoglycans such as lumican (LUM) induce the activation of the integrin signaling pathway, which serves a key role in cytoskeleton reorganization, cell motility and proliferation (6).…”