[翻译]<Circulation>2007年4月10日

Circulation. 2007;115:1830-1838
Arrhythmia/Electrophysiology

1、Targeted Mutation Reveals Essential Functions of the Homeodomain Transcription Factor Shox2 in Sinoatrial and Pacemaking Development
Rüdiger J. Blaschke, PhD; Nathan D. Hahurij, MSc; Sanne Kuijper, PhD*; Steffen Just, MD*; Lambertus J. Wisse, BSc; Kirsten Deissler, PhD; Tina Maxelon, BSc; Konstantinos Anastassiadis, PhD; Jessica Spitzer, MD; Stefan E. Hardt, MD; Hans Schöler, PhD; Harma Feitsma, BSc; Wolfgang Rottbauer, MD; Martin Blum, PhD; Frits Meijlink, PhD; Gudrun Rappold, PhD; Adriana C. Gittenberger-de Groot, PhD Abstract

Background— Identifying molecular pathways regulating the development of pacemaking and coordinated heartbeat is crucial for a comprehensive mechanistic understanding of arrhythmia-related diseases. Elucidation of these pathways has been complicated mainly by an insufficient definition of the developmental structures involved in these processes and the unavailability of animal models specifically targeting the relevant tissues. Here, we report on a highly restricted expression pattern of the homeodomain transcription factor Shox2 in the sinus venosus myocardium, including the sinoatrial nodal region and the venous valves.
Methods and Results— To investigate its function in vivo, we have generated mouse lines carrying a targeted mutation of the Shox2 gene. Although heterozygous animals did not exhibit obvious defects, homozygosity of the targeted allele led to embryonic lethality at 11.5 to 13.5 dpc. Shox2–/– embryos exhibited severe hypoplasia of the sinus venosus myocardium in the posterior heart field, including the sinoatrial nodal region and venous valves. We furthermore demonstrate aberrant expression of connexin 40 and connexin 43 and the transcription factor Nkx2.5 in vivo specifically within the sinoatrial nodal region and show that Shox2 deficiency interferes with pacemaking function in zebrafish embryos.
Conclusions— From these results, we postulate a critical function of Shox2 in the recruitment of sinus venosus myocardium comprising the sinoatrial nodal region.
Key Words: arrhythmia • genes • heart defects, congenital • heart rate • immunohistochemistry

2、Mechanistic Role of If Revealed by Induction of Ventricular Automaticity by Somatic Gene Transfer of Gating-Engineered Pacemaker (HCN) Channels
Tian Xue, PhD*; Chung-Wah Siu, MBBS*; Deborah K. Lieu, PhD; Chu-Pak Lau, MD; Hung-Fat Tse, MD; Ronald A. Li, PhD

Background— Although If, encoded by the hyperpolarization-activated cyclic-nucleotide-modulated (HCN) channel gene family, is known to be functionally important in pacing, its mechanistic action is largely inferential and indeed somewhat controversial. To dissect in detail the role of If, we investigated the functional consequences of overexpressing in adult guinea pig left ventricular cardiomyocytes (LVCMs) various HCN1 constructs that have been engineered to exhibit different gating properties.
Methods and Results— We created the recombinant adenoviruses Ad-CMV-GFP-IRES (CGI), Ad-CGI-HCN1, Ad-CGI-HCN1-, and Ad-CGI-HCN1-Ins, which mediate ectopic expression of GFP alone, WT, EVY235-7, and Ins HCN1 channels, respectively; EVY235-7 and Ins encode channels in which the S3–S4 linkers have been shortened and lengthened to favor and inhibit opening, respectively. Ad-CGI-HCN1, Ad-CGI-HCN1-, and Ad-CGI-HCN1-Ins, but not control Ad-CGI, transduction of LVCMs led to robust expression of If with comparable densities when fully open (–22 pA/pF at –140 mV; P>0.05) but distinctive activation profiles (V1/2=–70.8±0.6, –60.4±0.7, and –87.7±0.7 mV; P<0.01, respectively). Whereas control (nontransduced or Ad-CGI–transduced) LVCMs were electrically quiescent, automaticity (206±16 bpm) was observed exclusively in 61% of Ad-HCN1-–transduced cells that displayed depolarized maximum diastolic potential (–60.6±0.5 versus –70.6±0.6 mV of resting membrane potential of control cells; P<0.01) and gradual phase 4 depolarization (306±32 mV/s) that were typical of genuine nodal cells. Furthermore, spontaneously firing Ad-HCN1-–transduced LVCMs responded positively to adrenergic stimulation (P<0.05) but exhibited neither overdrive excitation nor suppression. In contrast, the remaining 39% of Ad-HCN1-–transduced cells exhibited no spontaneous action potentials; however, a single ventricular action potential associated with a depolarized resting membrane potential and a unique, incomplete "phase 4–like" depolarization that did not lead to subsequent firing could be elicited on simulation. Such an intermediate phenotype, similarly observed in 100% of Ad-CGI-HCN– and Ad-CGI-HCN1-Ins–transduced LVCMs, could be readily reversed by ZD7288, hinting at a direct role of If. Correlation analysis revealed the specific biophysical parameters required for If to function as an active membrane potential oscillator.
Conclusions— Our results not only contribute to a better understanding of cardiac pacing but also may advance current efforts that focus primarily on automaticity induction to the next level by enabling bioengineering of central and peripheral cells that make up the native sinoatrial node.
Key Words: genes • ion channels • pacemakers • sinoatrial node • tissue engineering

Coronary Heart Disease:
3、Comparison of Intravascular Ultrasound and Quantitative Coronary Angiography for the Assessment of Coronary Artery Disease Progression
Colin Berry, MD, PhD*; Philippe L. L’Allier, MD*; Jean Grégoire, MD; Jacques Lespérance, MD; Sylvie Levesque, MSc; Reda Ibrahim, MD; Jean-Claude Tardif, MD

Background— The relative merits of quantitative coronary analysis (QCA) and intravascular ultrasound (IVUS) for the assessment of progression/regression in coronary artery disease are uncertain. To explore this subject further, we analyzed the angiographic and IVUS data derived from a contemporary clinical trial population.
Methods and Results— We investigated the relationships between QCA and IVUS at single time points (n=525) and also for the changes over time (n=432). QCA and IVUS data underwent central laboratory analyses. Statistically significant correlations were observed between the QCA coronary artery score and the IVUS-derived lumen volume (r=0.65, P<0.0001) and total vessel volume (r=0.55, P<0.0001) and between the QCA cumulative coronary stenosis score and percent atheroma volume on IVUS (r=0.32, P<0.0001) at baseline for matched segments. A similar pattern of correlations was observed for global (all segments) QCA-derived and single-vessel IVUS-derived data. There were statistically significant but weak correlations between the changes over time in lumen dimensions on QCA and IVUS (P=0.005) and between the change in cumulative coronary stenosis score on QCA and percent atheroma volume on IVUS (r=0.14, P=0.01). Nevertheless, patients with and without angiographic progression had changes in plaque volume on IVUS of 9.13 and 0.20 mm3, respectively (P=0.028).
Conclusions— QCA- and IVUS-derived measures of lumen dimensions are correlated at single time points and for changes over time. Although the change in percent atheroma volume is only weakly correlated with QCA changes as continuous variables, disease progression on QCA is associated with significant increases in plaque volume on IVUS compared with no angiographic progression.
Key Words: angiography • atherosclerosis • coronary disease • ultrasonics

4、A Prospective Study of Trans Fatty Acids in Erythrocytes and Risk of Coronary Heart Disease
Qi Sun, MD; Jing Ma, MD, PhD; Hannia Campos, PhD; Susan E. Hankinson, ScD; JoAnn E. Manson, MD, DrPH; Meir J. Stampfer, MD, DrPH; Kathryn M. Rexrode, MD, MPH; Walter C. Willett, MD, DrPH; Frank B. Hu, MD, PhD

Background— High consumption of trans fat has been linked to the risk of coronary heart disease (CHD). We assessed the hypothesis that higher trans fatty acid contents in erythrocytes were associated with an elevated risk of CHD in a nested case-control study among US women.
Methods and Results— Blood samples were collected from 32 826 participants of the Nurses’ Health Study from 1989 to 1990. During 6 years of follow-up, 166 incident cases of CHD were ascertained and matched with 327 controls. Total trans fatty acid content in erythrocytes was significantly correlated with dietary intake of trans fat (correlation coefficient=0.44, P<0.01) and was associated with increased plasma low-density lipoprotein cholesterol (P for trend =0.06), decreased plasma high-density lipoprotein cholesterol concentrations (P for trend <0.01), and increased plasma low-density lipoprotein to high-density lipoprotein ratio (P for trend <0.01). After adjustment for age, smoking status, and other dietary and lifestyle cardiovascular risk factors, higher total trans fatty acid content in erythrocytes was associated with an elevated risk of CHD. The multivariable relative risks (95% confidence intervals) of CHD from the lowest to highest quartiles of total trans fatty acid content in erythrocytes were 1.0 (reference), 1.6 (0.7 to 3.6), 1.6 (0.7 to 3.4), and 3.3 (1.5 to 7.2) (P for trend <0.01). The corresponding relative risks were 1.0, 1.1, 1.3, and 3.1 (P for trend <0.01) for a total of 18:1 trans isomers and 1.0, 1.5, 2.5, and 2.8 (P for trend <0.01) for a total of 18:2 trans isomers.
Conclusions— These biomarker data provide further evidence that high trans fat consumption remains a significant risk factor for CHD after adjustment for covariates.
Key Words: blood cells • coronary disease • fatty acids • women

Heart Failure:
5、Bioenergetic and Functional Consequences of Bone Marrow–Derived Multipotent Progenitor Cell Transplantation in Hearts With Postinfarction Left Ventricular Remodeling
Lepeng Zeng, PhD*; Qingsong Hu, MD, MS*; Xiaohong Wang, MD, PhD*; Abdul Mansoor, MD, PhD; Joseph Lee, PhD; Julia Feygin, BS; Ge Zhang, MD, PhD; Piradeep Suntharalingam, BS;

Background— The present study examined whether transplantation of adherent bone marrow–derived stem cells, termed pMultistem, induces neovascularization and cardiomyocyte regeneration that stabilizes bioenergetic and contractile function in the infarct zone and border zone (BZ) after coronary artery occlusion.
Methods and Results— Permanent left anterior descending artery occlusion in swine caused left ventricular remodeling with a decrease of ejection fraction from 55±5.6% to 30±5.4% (magnetic resonance imaging). Four weeks after left anterior descending artery occlusion, BZ myocardium demonstrated profound bioenergetic abnormalities, with a marked decrease in subendocardial phosphocreatine/ATP (31P magnetic resonance spectroscopy; 1.06±0.30 in infarcted hearts [n=9] versus 1.90±0.15 in normal hearts [n=8; P<0.01]). This abnormality was significantly improved by transplantation of allogeneic pMultistem cells (subendocardial phosphocreatine/ATP to 1.34±0.29; n=7; P<0.05). The BZ protein expression of creatine kinase–mt and creatine kinase–m isoforms was significantly reduced in infarcted hearts but recovered significantly in response to cell transplantation. MRI demonstrated that the infarct zone systolic thickening fraction improved significantly from systolic "bulging" in untreated animals with myocardial infarction to active thickening (19.7±9.8%, P<0.01), whereas the left ventricular ejection fraction improved to 42.0±6.5% (P<0.05 versus myocardial infarction). Only 0.35±0.05% donor cells could be detected 4 weeks after left anterior descending artery ligation, independent of cell transplantation with or without immunosuppression with cyclosporine A (with cyclosporine A, n=6; no cyclosporine A, n=7). The fraction of grafted cells that acquired an endothelial or cardiomyocyte phenotype was 3% and 2%, respectively. Patchy spared myocytes in the infarct zone were found only in pMultistem transplanted hearts. Vascular density was significantly higher in both BZ and infarct zone of cell-treated hearts than in untreated myocardial infarction hearts (P<0.05).
Conclusions— Thus, allogeneic pMultistem improved BZ energetics, regional contractile performance, and global left ventricular ejection fraction. These improvements may have resulted from paracrine effects that include increased vascular density in the BZ and spared myocytes in the infarct zone.
Key Words: cells • heart failure • hypertrophy • magnetic resonance imaging • metabolism • myocardial contraction • myocardial infarction

Molecular Cardiology:
6、Targeted Cardiac Overexpression of A20 Improves Left Ventricular Performance and Reduces Compensatory Hypertrophy After Myocardial Infarction
Hong-Liang Li, Ming-Lei Zhuo, Dong Wang, Ai-Bing Wang, Hua Cai, Li-Hong Sun, Qinglin Yang, Yue Huang, Yu-Sheng Wei, Peter P. Liu, De-Pei Liu, and Chih-Chuan Liang

Background— A20 was originally characterized as a tumor necrosis factor–inducible gene in human umbilical vein endothelial cells. As an inhibitor of nuclear factor-B signaling, A20 protects against apoptosis, inflammation, and cardiac hypertrophy. In the present study, we tested the hypothesis that cardiac-specific overexpression of A20 could protect the heart from myocardial infarction.
Methods and Results— We investigated the role of constitutive human A20 expression in acute myocardial infarction using a transgenic model. Transgenic mice containing the human A20 gene under the control of the -myosin heavy chain promoter were constructed. Myocardial infarction was produced by coronary ligation in A20 transgenic mice and control animals. The extent of infarction was then quantified by 2-dimensional and M-mode echocardiography and by molecular and pathological analyses of heart samples in infarct and remote heart regions 7 days after myocardial infarction. Constitutive overexpression of A20 in the murine heart resulted in attenuated infarct size and improved cardiac function 7 days after myocardial infarction. Significantly, we found a decrease in nuclear factor-B signaling and apoptosis, as well as proinflammatory response, cardiac remodeling, and interstitial fibrosis, in noninfarct regions in the hearts of constitutive A20-expressing animals compared with control animals.
Conclusions— Cardiac-specific overexpression of A20 improves cardiac function and inhibits cardiac remodeling, apoptosis, inflammation, and fibrosis after acute myocardial infarction.
Key Words: apoptosis • cardiovascular diseases • fibrosis • gene therapy • hypertrophy • inflammation • remodeling

7、The pH Hypothesis of Postconditioning
Staccato Reperfusion Reintroduces Oxygen and Perpetuates Myocardial Acidosis
Michael V. Cohen, MD; Xi-Ming Yang, MD, PhD; James M. Downey, PhD

Background— It is unclear how reperfusion of infarcting hearts with alternating cycles of coronary reperfusion/occlusion attenuates infarction, but prevention of mitochondrial permeability transition pore (MPTP) formation is crucial. Acidosis also suppresses MPTP formation. We tested whether postconditioning protects by maintaining acidosis during early reoxygenation.
Methods and Results— After 30-minute regional ischemia in isolated rabbit hearts, reperfusion with buffer (pH 7.4) caused 34.4±2.2% of the risk zone to infarct, whereas 2 minutes of postconditioning (6 cycles of 10-second reperfusion/10-second occlusion) at reperfusion resulted in 10.7±2.9% infarction. One minute (3 cycles) of postconditioning was not protective. Hypercapnic buffer (pH 6.9) for the first 2 minutes of reperfusion in lieu of postconditioning caused equivalent cardioprotection (15.0±2.6% infarction), whereas 1 minute of acidosis did not protect. Delaying postconditioning (6 cycles) or 2 minutes of acidosis for 1 minute aborted protection. Reperfusion with buffer (pH 7.7) blocked postconditioning protection, but addition of the MPTP closer cyclosporin A restored protection. Reactive oxygen species scavenger N-2-mercaptopropionyl glycine, protein kinase C antagonist chelerythrine, and mitochondrial KATP channel closer 5-hydroxydecanoate each blocked protection from 2 minutes of acidosis as they did for postconditioning.
Conclusion— Thus, postconditioning prevents MPTP formation by maintaining acidosis during the first minutes of reperfusion as reoxygenated myocardium produces reactive oxygen species that activate protective signaling to inhibit MPTP formation after pH normalization.
Key Words: acidosis • free radicals • mitochondrial permeability transition pore • myocardial infarction • reperfusion

8、Targeted Deletion of Class A Macrophage Scavenger Receptor Increases the Risk of Cardiac Rupture After Experimental Myocardial Infarction
Kenichi Tsujita, MD; Koichi Kaikita, MD; Takanori Hayasaki, MD; Tsuyoshi Honda, MD; Hironori Kobayashi, MD; Naomi Saka***a, MD; Hiroshi Suzuki, PhD; Tatsuhiko Kodama, MD; Hisao Ogawa, MD; Motohiro Takeya, MD

Background— Class A macrophage scavenger receptor (SR-A) is a macrophage-restricted multifunctional molecule that optimizes the inflammatory response by modulation of the activity of inflammatory cytokines. This study was conducted with SR-A–deficient (SR-A–/–) mice to evaluate the relationship between SR-A and cardiac remodeling after myocardial infarction.
Methods and Results— Experimental myocardial infarction (MI) was produced by ligation of the left coronary artery in SR-A–/– and wild-type (WT) male mice. The number of mice that died within 4 weeks after MI was significantly greater in SR-A–/– mice than in WT mice (P=0.03). Importantly, death caused by cardiac rupture within 1 week after MI was 31% (17 of 54 mice) in SR-A–/– mice and 12% (6 of 51 mice) in WT mice (P=0.01). In situ zymography demonstrated augmented gelatinolytic activity in the infarcted myocardium in SR-A–/– mice compared with WT mice. Real-time reverse transcription–polymerase chain reaction at day 3 after MI showed that the expression of matrix metalloproteinase-9 mRNA increased significantly in the infarcted myocardium in SR-A–/– mice compared with WT mice. Furthermore, SR-A–/– mice showed augmented expression of tumor necrosis factor- and reduction of interleukin-10 in the infarcted myocardium at day 3 after MI. In vitro experiments also demonstrated increased tumor necrosis factor- and decreased interleukin-10 expression in activated SR-A–/– macrophages.
Conclusions— The present findings suggest that SR-A deficiency might cause impairment of infarct remodeling that results in cardiac rupture via insufficient production of interleukin-10 and enhanced expression of tumor necrosis factor- and of matrix metalloproteinase-9. SR-A might contribute to the prevention of cardiac rupture after MI.
Key Words: cytokines • macrophages • myocardial infarction • receptors • remodeling

9、Targeted Deletion of Class A Macrophage Scavenger Receptor Increases the Risk of Cardiac Rupture After Experimental Myocardial Infarction
Kenichi Tsujita, MD; Koichi Kaikita, MD; Takanori Hayasaki, MD; Tsuyoshi Honda, MD; Hironori Kobayashi, MD; Naomi Saka***a, MD; Hiroshi Suzuki, PhD; Tatsuhiko Kodama, MD; Hisao Ogawa, MD; Motohiro Takeya, MD

Background— Class A macrophage scavenger receptor (SR-A) is a macrophage-restricted multifunctional molecule that optimizes the inflammatory response by modulation of the activity of inflammatory cytokines. This study was conducted with SR-A–deficient (SR-A–/–) mice to evaluate the relationship between SR-A and cardiac remodeling after myocardial infarction.
Methods and Results— Experimental myocardial infarction (MI) was produced by ligation of the left coronary artery in SR-A–/– and wild-type (WT) male mice. The number of mice that died within 4 weeks after MI was significantly greater in SR-A–/– mice than in WT mice (P=0.03). Importantly, death caused by cardiac rupture within 1 week after MI was 31% (17 of 54 mice) in SR-A–/– mice and 12% (6 of 51 mice) in WT mice (P=0.01). In situ zymography demonstrated augmented gelatinolytic activity in the infarcted myocardium in SR-A–/– mice compared with WT mice. Real-time reverse transcription–polymerase chain reaction at day 3 after MI showed that the expression of matrix metalloproteinase-9 mRNA increased significantly in the infarcted myocardium in SR-A–/– mice compared with WT mice. Furthermore, SR-A–/– mice showed augmented expression of tumor necrosis factor- and reduction of interleukin-10 in the infarcted myocardium at day 3 after MI. In vitro experiments also demonstrated increased tumor necrosis factor- and decreased interleukin-10 expression in activated SR-A–/– macrophages.
Conclusions— The present findings suggest that SR-A deficiency might cause impairment of infarct remodeling that results in cardiac rupture via insufficient production of interleukin-10 and enhanced expression of tumor necrosis factor- and of matrix metalloproteinase-9. SR-A might contribute to the prevention of cardiac rupture after MI.
Key Words: cytokines • macrophages • myocardial infarction • receptors • remodeling

Valvular Heart Disease:
10、Mutations in FOXC2 Are Strongly Associated With Primary Valve Failure in Veins of the Lower Limb
Russell H. Mellor, PhD; Glen Brice, BSc; Anthony W.B. Stanton, PhD; Jane French, MSc; Alberto Smith, PhD; Steve Jeffery, PhD; J. Rodney Levick, DSc, MRCP; Kevin G. Burnand, MS, FRCS; Peter S. Mortimer, MD, FRCP

Background— Mutations in the FOXC2 gene cause lymphedema distichiasis, an inherited primary lymphedema in which a significant number of patients have varicose veins. Because lymphedema distichiasis is believed to be caused by lymphatic valve failure (reflux), and FOXC2 is highly expressed on venous valves in mouse embryos, we tested the hypothesis that FOXC2 mutations may be linked to venous valve failure and reflux.
Methods and Results— The venous system of the leg was investigated with Duplex ultrasound. Pathological reflux was recorded by color Duplex ultrasound in all 18 participants with a FOXC2 mutation, including 3 without lymphedema. Every participant with a mutation in FOXC2 showed reflux in the great saphenous vein (n=18), compared with only 1 of 12 referents (including 10 family members; P<0.0001, Fisher exact test). Deep vein reflux was recorded in 14 of 18 participants.
Conclusions— FOXC2 is the first gene in which mutations have been strongly associated with primary venous valve failure in both the superficial and deep veins in the lower limb. This gene appears to be important for the normal development and maintenance of venous and lymphatic valves.
Key Words: valves • genes • patients • ultrasonics • veinslymphedema