Decreased Perivascular Fibrosis but Not Cardiac Hypertrophy in ROCK1 ^+/− Haploinsufficient Mice

Abstract

Background-Rho GTPase and its downstream target, Rho-associated kinase (ROCK), have been implicated in diverse cardiovascular diseases such as cardiac hypertrophy. However, pharmacological inhibitors of ROCK are not entirely specific, nor can they discriminate between the ROCK isoforms ROCK1 and ROCK2. To determine the specific role of ROCK1 in the development of cardiac hypertrophy, we generated ROCK1 ϩ/Ϫ haploinsufficient mice and determined whether cardiac hypertrophy and remodeling are decreased in these mice. Methods and Results-Litters of ROCK1Ϫ/Ϫ mice on C57Bl/6 background were markedly underrepresented, suggesting lethality in utero or postnatally. ROCK1 ϩ/Ϫ mice, however, are viable and fertile with no obvious phenotypic abnormalities. Basal blood pressure, heart rate, and cardiac dimension and function in ROCK1 ϩ/Ϫ mice were similar to those in wild-type (WT) littermates. Infusion of angiotensin II (400 ng · kg Ϫ1 · min Ϫ1 for 28 days) or treatment with N G -nitro-L-arginine methyl ester (1 mg/mL in drinking water for 28 days) caused similar increases in systolic blood pressure, left ventricular wall thickness, left ventricular mass, ratio of heart weight to tibial length, and cardiomyocyte size in ROCK1 ϩ/Ϫ mice and WT littermates. In contrast, perivascular fibrosis in hearts was increased to a lesser extent in ROCK1ϩ/Ϫ mice compared with WT littermates. This was associated with decreased expression of transforming growth factor-␤, connective tissue growth factor, and type III collagen. In addition, perivascular fibrosis induced by transaortic constriction or myocardial infarction was decreased in ROCK1 ϩ/Ϫ mice compared with WT littermates. Conclusions-These findings indicate ROCK1 is critical for the development of cardiac fibrosis, but not hypertrophy, in response to various pathological conditions and suggest that signaling pathways leading to the hypertrophic and profibrotic response of the heart are distinct.

Endothelial dysfunction and hypertension in aging

“…97,98 Indeed, the RhoA/ROCK pathway has been shown to be involved in the formation of atherosclerotic lesions, vasoconstriction and myocardial hypertrophy and to be activated in patients with hypertension and in patients with coronary artery disease. [99][100][101][102][103][104] Recently, we have shown that FMD is an independent predictor of leukocyte ROCK activity in healthy men and men with cardiovascular risk factors but without established cardiovascular or cerebrovascular diseases, suggesting that cumulative cardiovascular risk, including aging and hypertension, may enhance ROCK activity and endothelial dysfunction. 105 Activation of the RhoA/ROCK pathway impairs NO bioavailability through inhibition of eNOS mRNA stability, eNOS posphorylation at Ser 1177 and the Akt/PI3K pathway and enhancement of eNOS phosphorylation at Thr495.…”

Rho kinase in the regulation of cell death and survival

“…Recently ROCK1-knockout (ROCK1 -/-) and ROCK2-knockout (ROCK2 -/-) mice have been generated [115,122,135,153] and their phenotypes are different. ROCK1 -/-mice under C57BL/ 6N genetic background exhibit eyelid open at birth (EOB) and omphalocele phenotype due to disorganization of actin filament in the epithelial cells of the eyelid and of the umbilical ring [122].…”

“…The genetic background may also affect the EOB and omphalocele phenotype in ROCK1 -/-mice, as this phenotype was not observed in ROCK1 -/-mice under the mixed C57BL/6N-129/ SvJ or FVB background [153], although the differences in targeting vector may also contribute to the different phenotype of ROCK1 -/-mice generated by different laboratories [115,122,153]. In addition, the ROCK1 -/-mice under FVB background have no detected anatomical abnormalities from embryonic day 9.5 to adulthood, although they are underrepresented, possibly due to lethality at very early developmental stages [153].…”

Rock1 & 2 Perform Overlapping and Unique Roles in Angiogenesis and Angiosarcoma Tumor Progression

“…The two ROCK paralogs share 65% identity overall and 92% identity in their kinase domains [32] and ROCK1 & 2 knockout mice display unique phenotypes [3, 5-7], suggesting that their regulation and signaling may be divergent to a measurable degree. Indeed, comparisons of RNAi knockdowns of the individual ROCK paralogs across a handful of cell types uncovered unique roles for each paralog in actin organization, migration, cellular morphogenesis, cell cycle progression, apoptosis, and extracellular matrix assembly [8-10, 12, 13, 33].…”

“…ROCK1(-/-) mice result in lethality soon after birth, displaying failure of eyelid and ventral body wall closure [3], while ROCK2(-/-) mice experience embryonic lethality due to interuterine growth retardation and placental dysfunction [4]. Viable fertile litters have been reported for ROCK1(+/-) and ROCK2(+/-) mice, however ROCK1(+/-) mice exhibit increased resistance to perivascular fibrosis and reduced vascular injury-induced neointima formation [5, 6], while ROCK2(+/-) mice display decreased platelet endothelial cell adhesion molecule staining of endothelial cells in the lung [7]. Only a handful of recent reports have utilized RNAi technology to singularly disrupt each ROCK paralog in vitro , demonstrating unique roles for each protein in the control of actin-cytoskeleton dynamics and cell morphogenesis, migration, cell fate decisions, and extracellular matrix assembly [7-13].…”