ROCK Controls Matrix Synthesis in Vascular Smooth Muscle Cells

Abstract

Abstract-Tenascin-C (TN-C) is an extracellular matrix (ECM) protein expressed within remodeling systemic and pulmonary arteries (PAs), where it supports vascular smooth muscle cell (SMC) proliferation. Previously, we showed that A10 SMCs cultivated on native type I collagen possess a spindle-shaped morphology and do not express TN-C, whereas those on denatured collagen possess a well-defined F-actin stress fiber network, a spread morphology, and they do express TN-C. To determine whether changes in cytoskeletal architecture control TN-C, SMCs on denatured collagen were treated with cytochalasin D, which decreased SMC spreading and activation of extracellular signal-regulated kinase 1/2 (ERK1/2), signaling effectors required for TN-C transcription. Next, to determine whether cell shape, dictated by the F-actin cytoskeleton, regulates TN-C, different geometries of SMCs (ranging from spread to round) were engineered on denatured collagen: as SMCs progressively rounded, ERK1/2 activity and TN-C transcription declined. Because RhoA and Rho kinase (ROCK) regulate cell morphology by controlling cytoskeletal architecture, we reasoned that these factors might also regulate TN-C. Indeed, SMCs on denatured collagen possessed higher levels of RhoA activity than those on native collagen, and blocking RhoA or ROCK activities attenuated SMC spreading, ERK1/2 activity, and TN-C expression in SMCs on denatured collagen. Thus, ROCK controls the configuration of the F-actin cytoskeleton and SMC shape in a manner that is permissive for ERK1/2-dependent production of TN-C. Finally, we showed that inhibition of ROCK activity suppresses SMC TN-C expression and disease progression in hypertensive rat PAs. Thus, in addition to its role in regulating vasoconstriction, ROCK also controls matrix production. (Circ Res. 2006;99:837-844.)Key Words: tenascin-C Ⅲ smooth muscle Ⅲ ROCK Ⅲ pulmonary hypertension A dult vascular smooth muscle cells (SMCs) reside within a type I collagen-enriched extracellular matrix (ECM) that helps to maintain the majority of these cells in a nonmotile, growth-arrested, and differentiated state. 1-4 Following vascular injury, however, ECM-degrading matrix metalloproteinases (MMPs) remodel the preexisting ECM to create a tissue microenvironment that is conducive for SMC proliferation, migration, and survival. [3][4][5] Understanding how alterations in adhesive interactions within the vascular ECM modify SMC behavior, therefore, represents an important question in vascular pathobiology.Tenascin-C (TN-C) is an ECM glycoprotein induced within remodeling hypertensive pulmonary arteries (PAs), 6 -10 as well as in systemic, obliterative vasculopathies, [11][12][13] where it supports vascular SMC proliferation, migration, and survival. 4,14,15 In keeping with the idea that TN-C plays a direct role in promoting vascular disease, studies using TN-C null mice demonstrate that these animals are refractory to neointimal hyperplasia after aortotomy. 11 Further, blocking TN-C expression in cultured hypertensive rat PAs induces ...

Low Intensity Pulsed Ultrasound (LIPUS) Influences the Multilineage Differentiation of Mesenchymal Stem and Progenitor Cell Lines through ROCK-Cot/Tpl2-MEK-ERK Signaling Pathway

“…Activation of ROCK by mechanical stimuli other than LIPUS has been reported in several cell types (68,69). A quite recent report, which was published when our study was ongoing, has examined the role of ROCK in mechanical stress-induced MSC differentiation (70).…”

Cell cycle dependent TN‐C promoter activity determined by live cell imaging

“…collagen, for example, are poorly spread, do not proliferate, and do not produce TN-C, while cells on denatured collagen develop a well-spread morphology, have well-organized cytoskeleton, are proliferative, and produce TN-C (19). If vascular smooth muscle cells are prevented from spreading, through treatment with cytochalasin or by physical means, TN-C production is blocked, as is activation of ERK1/2, a known mitogen (19).…”

“…If vascular smooth muscle cells are prevented from spreading, through treatment with cytochalasin or by physical means, TN-C production is blocked, as is activation of ERK1/2, a known mitogen (19). Similarly, conditions that arrest cell cycle progress and result in differentiation in mammary and vascular smooth muscle cells are accompanied by down-regulation of TN-C expression (20)(21)(22).…”

RhoA-Dependent Vascular Smooth Muscle Cell–Specific Transcription

“…In fact, Dia1 is also recruited to endosomes by activated RhoB. 8 A comparison of Dia1/2 activity with other RhoA effectors including ROK 9 and PKN 10 is also necessary to identify the dominating or overlapping signaling pathways that regulate SMC-specific transcription. These different RhoA effectors may positively or negatively operate with each other in a cell-specific manner.…”