Rationale: Despite contemporary therapy, coronary artery disease (CAD) remains a leading cause of mortality. Genetic variants at ADAMTS7 have been associated with CAD and the loss of ADAMTS7 is protective for atherosclerosis. ADAMTS7 (a disintegrin and metalloproteinase with thrombospondin motifs 7) is a secreted metalloproteinase and complex proteoglycan, yet the mechanism linking ADAMTS7 to CAD risk remains unresolved. Objective: To investigate the role of ADAMTS7 catalytic function in vascular smooth muscle cellular migration and during atherosclerosis. Methods and Results: We established a new purification strategy for full-length mouse ADAMTS7 and demonstrated the loss of activity in the catalytic mutant form of ADAMTS7. To test if the enzymatic activity of ADAMTS7 mediates atherosclerosis, we generated a catalytically inactive mutant mouse allele and compared it to the Adamts7 knockout. Using two models of atherosclerosis, we found that reducing either ADAMTS7 dosage or catalytic function decreased the burden of atherosclerosis. We demonstrate impaired vascular smooth muscle migration in both Adamts7 catalytic mutant and null cells using a lateral migration wound healing assay. Expression of the wild-type allele rescued the migration phenotype in Adamts7 null cells while expression of the catalytic mutant protein did not. We then characterized a human ADAMTS7 coding variant rs3825807 (Ser214Pro) associated with reduced CAD risk. This variant had a hypomorphic effect on ADAMTS7 secretion and migration of vascular smooth muscle cells (VSMC), findings consistent with our mouse studies. Conclusions: We demonstrated that loss of ADAMTS7 catalytic function protects against atherosclerosis via phenotype switch of VSMCs and that the atherosclerosis protective effects could be mediated by a loss-of-function coding variant associated with CAD risk. In aggregate, we provide compelling evidence that dosage of ADAMTS7 and catalytic function are responsible for the atherosclerotic phenotype, suggesting that the catalytic domain would be an attractive therapeutic target for CAD.

Rationale: Hypertrophic cardiomyopathy occurs with a frequency of about 1 in 500 people. Approximately 30% of those affected carry mutations within the gene encoding cardiac myosin-binding protein C (cMyBP-C). Cardiac stress, as well as cMyBP-C mutations, can trigger production of a 40kDa truncated fragment derived from the amino terminus of cMyBP-C (Mybpc340kDa). Expression of the 40kDa fragment in mouse cardiomyocytes leads to hypertrophy, fibrosis and heart failure. Here we use genetic approaches to establish a causal role for excessive myofibroblast activation in a slow, progressive genetic cardiomyopathy - one that is driven by a cardiomyocyte-intrinsic genetic perturbation that models an important human disease. Objective: Transforming growth factor-β (TGFβ) signaling is implicated in a variety of fibrotic processes and the goal of this study was to define the role of myofibroblast TGFβ signaling during chronic Mybpc340kDa expression. Methods and Results: To specifically block TGFβ signaling only in the activated myofibroblasts in Mybpc340kDa transgenic (Tg) mice, quadruple compound mutant mice were generated, in which the TGFβ receptor II (TβRII) alleles (Tgfbr2) were ablated using the Postn (periostin) allele, myofibroblast-specific, tamoxifen-inducible Cre (Postnmcm) gene-targeted line. Tgfbr2 was ablated either early or late during pathological fibrosis. Early myofibroblast specific Tgfbr2 ablation during the fibrotic response reduced cardiac fibrosis, alleviated cardiac hypertrophy, preserved cardiac function, and increased lifespan of the Mybpc340kDa Tg mice. Tgfbr2 ablation late in the pathological process reduced cardiac fibrosis, preserved cardiac function, and prolonged Mybpc340kDa mouse survival but failed to reverse cardiac hypertrophy. Conclusions: Fibrosis and cardiac dysfunction induced by cardiomyocyte-specific expression of Mybpc340kDa were significantly decreased by Tgfbr2 ablation in the myofibroblast. Surprisingly, pre-existing fibrosis was partially reversed if the gene was ablated subsequent to fibrotic deposition, suggesting that continued TGFβ signaling through the myofibroblasts was needed to maintain the heart’s fibrotic response to a chronic, disease-causing cardiomyocyte-only stimulus.

Cardiac myosin-binding protein C (cMyBP-C) is an integral part of the sarcomeric machinery in cardiac muscle that enables normal function. cMyBP-C regulates normal cardiac contraction by functioning as a brake through interactions with the sarcomere's thick, thin, and titin filaments. cMyBP-C's precise effects as it binds to the different filament systems remain obscure, particularly as it impacts on the myosin heavy chain's head domain, contained within the subfragment 2 (S2) region. This portion of the myosin heavy chain also contains the ATPase activity critical for myosin's function. Mutations in myosin's head, as well as in cMyBP-C, are a frequent cause of familial hypertrophic cardiomyopathy (FHC). We generated transgenic lines in which endogenous cMyBP-C was replaced by protein lacking the residues necessary for binding to S2 (cMyBP-C S2− ). We found, surprisingly, that cMyBP-C lacking the S2 binding site is incorporated normally into the sarcomere, although systolic function is compromised. We show for the first time the acute and chronic in vivo consequences of ablating a filament-specific interaction of cMyBP-C. This work probes the functional consequences, in the whole animal, of modifying a critical structure-function relationship, the protein's ability to bind to a region of the critical enzyme responsible for muscle contraction, the subfragment 2 domain of the myosin heavy chain. We show that the binding is not critical for the protein's correct insertion into the sarcomere's architecture, but is essential for long-term, normal function in the physiological context of the heart.

Background Transforming growth factor beta ( TGF ‐β) is an important cytokine in mediating the cardiac fibrosis that often accompanies pathogenic cardiac remodeling. Cardiomyocyte‐specific expression of a mutant αB‐crystallin (Cry AB R 120G ), which causes human desmin‐related cardiomyopathy, results in significant cardiac fibrosis. During onset of fibrosis, fibroblasts are activated to the so‐called myofibroblast state and TGF ‐β binding mediates an essential signaling pathway underlying this process. Here, we test the hypothesis that fibroblast‐based TGF ‐β signaling can result in significant cardiac fibrosis in a disease model of cardiac proteotoxicity that has an exclusive cardiomyocyte‐based etiology. Methods and Results Against the background of cardiomyocyte‐restricted expression of Cry AB R 120G , we have partially ablated TGF ‐β signaling in cardiac myofibroblasts to observe whether cardiac fibrosis is reduced despite the ongoing pathogenic stimulus of Cry AB R 120G production. Transgenic Cry AB R 120G mice were crossed with mice containing a floxed allele of TGF ‐β receptor 2 ( Tgfbr2 f/f ). The double transgenic animals were subsequently crossed to another transgenic line in which Cre expression was driven from the periostin locus ( Postn ) so that Tgfbr2 would be ablated with myofibroblast conversion. Structural and functional assays were then used to determine whether general fibrosis was affected and cardiac function rescued in Cry AB R 120G mice lacking Tgfbr2 in the myofibroblasts. Ablation of myofibroblast specific TGF ‐β signaling led to decreased morbidity in a proteotoxic disease resulting from cardiomyocyte autonomous expression of Cry AB R 120G . Cardiac fibrosis was decreased and hypertrophy was also significantly attenuated, with a significant improvement in survival probability over time, even though the primary proteotoxic insult continued. Conclusions Myofibroblast‐targeted knockdown of Tgfbr2 signaling resulted in reduced fibrosis and improved cardiac function, leading to improved probability of survival.

Background: Various studies have suggested that support from a patient's family can facilitate his/her recovery from a physical illness and improve the ability of the patient to deal with consequences of Type 2 Diabetes. Stress is considered to play a major role in influencing Type 2 Diabetes Mellitus.