跑步训练诱导小鼠生理性心脏肥厚模型

目的用长期跑步训练诱导小鼠的生理性心脏肥厚模型,与主动脉缩窄手术诱导的病理性心脏肥厚模型进行比较。方法 8周龄野生型雄性C57BL/6小鼠分为跑步运动组,正常对照组,手术刺激组和假手术组。运动组跑步训练40d,手术刺激组行主动脉缩窄手术2周,从组织形态学、超声心动图、分子标志物表达等方面对模型进行全面评估。结果运动训练组小鼠心脏体重比与正常对照组相比增加27.2%(P<0.05),左心室体重比增加25.8%(P<0.01),心脏显著肥厚。超声心动图显示,与各自的对照组相比,运动组和手术组小鼠模型的左心室后壁厚度均显著增加(P<0.05),但运动组小鼠的相对室壁厚度无明显变化,而手术组小鼠相对室壁厚度显著增加50%(P<0.05),提示两种不同的心脏肥厚导致在心脏结构改变上差别显著。心脏肥厚分子标志物心房利钠肽和脑钠肽在手术组表达显著上调9.5倍和4.5倍,而在运动组下调为对照组的0.48倍和0.58倍,提示两种不同肥厚的分子机制差别迥异。结论长期跑步运动可以成功的诱导小鼠生理性心脏肥厚模型,其表型和分子机制与手术刺激的病理性肥厚差别显著。     

RASSF1A: A potential novel therapeutic target against cardiac hypertrophy

Cardiac hypertrophy is a key risk factor for chronic heart failure. Current treatments predominantly focus on both reducing the peripheral vascular resistance and activating nerve-humoral system. However, these efforts can't reverse cardiac hypertrophy fundamentally. Ras association domain family 1 isoform A (RASSF1A) is a regulatory tumor suppressor whose inactivation by inappropriate promoter methylation has been implicated in the development of many human cancers. Recently, there have been a number of studies investigating the roles of RASSF1A in the pathophysiology of cardiac hypertrophy. In this review, we focus on the present progresses of cardiac RASSF1A under physiological and pathological conditions, trying to systematically elucidate how the RASSF1A-mediated signal pathways contribute to the maintenance of normal cardiac myocyte structure and function and lead to the regression of pathological cardiac hypertrophy. These pathways exert multiple functions such as regulating cardiac contractility, physiologically increasing stability of microtubule, preventing cardiac dysfunction, attenuating interstitial fibrosis and mediating cell apoptosis. These specific roles are highly relevant with cardiac hemodynamics and therapeutic strategies, indicating RASSF1A may have the potential to reverse pathological cardiac hypertrophy thus prevent heart failure fundamentally.     

A novel porcupine inhibitor blocks WNT pathways and attenuates cardiac hypertrophy

WNT pathways are critically involved in the cardiac hypertrophy growth. Porcupine, an acyltransferase that specifically enables secretion of all WNT ligands, became a highly druggable target for inhibiting WNT pathways. Here we test if a novel small-molecule porcupine inhibitor CGX1321, which has entered human clinical trials as an anti-cancer agent, exerts an anti-hypertrophic effect. Transverse aortic constriction (TAC) was performed to induce cardiac hypertrophy on four-month-old male C57 mice. Cardiac function was measured with echocardiography. Histological analysis was performed to detect cardiomyocyte size and molecular expressions. CGX1321 was administrated daily for 4?weeks post TAC injury. As a result, CGX1321 improved cardiac function and animal survival of post-TAC mice. CGX1321 significantly reduced cardiomyocyte hypertrophy, cardiomyocyte apoptosis and fibrosis induced by TAC injury. CGX1321 significantly inhibited TAC induced nuclear translocation of β-catenin and the elevation of Frizzled-2, cyclin-D1 and c-myc expression, indicating its inhibitory effect on canonical WNT pathway. Furthermore, CGX1321 inhibited TAC induced nuclear translocation of nuclear factor of activated T-cells and the elevation of phosphorylated c-Jun expression, suggesting its inhibitory function on non-canonical WNT pathway. We conclude that CGX1321 inhibits both canonical and non-canonical WNT pathways, and attenuates cardiac hypertrophy. Our findings support the porcupine inhibitors as a class of new drugs to be potentially used for treating patients with cardiac hypertrophy.     

A novel cardiac hypertrophic factor, neurotrophin-3, is paradoxically downregulated in cardiac hypertrophy

The neurotrophin family plays pivotal roles in the development of the nervous system. Recently, the role of the neurotrophin in non-neural tissue has been extensively investigated. Among them, neurotrophin-3 and its receptor TrkC are critical for embryonic heart development, though little is known about neurotrophin-3/TrkC function in adult heart. Moreover, the expressions of other neurotrophin and Trk families in the cardiovascular system have not been fully determined. In adult and neonatal rats, only TrkC mRNA was expressed more abundantly in heart than aorta among the neurotrophin receptors, while all neurotrophins were equally expressed in the cardiovascular system. Immunohistochemistry confirmed the protein expressions of neurotrophin-3/TrkC in rat ventricles. In primary-cultured rat cardiomyocytes, neurotrophin-3 strongly activated p38 mitogen-activated protein kinase, extracellular signal-regulated kinase 1/2, and Jun N-terminal kinase pathways in Western blot analysis. In Northern blot analysis, neurotrophin-3 strongly increased mRNA expressions of cardiac hypertrophic markers (skeletal alpha-actin and atrial natriuretic peptide) in cardiomocytes. [(3)H]-phenylalanine uptake into cardiomyocytes, myofilament reorganization, and cardiomyocyte size were also augmented with neurotrophin-3 stimulation, indicating that neurotrophin-3 is a novel cardiac hypertrophic factor. Unexpectedly, neurotrophin-3 was downregulated in cardiac hypertrophy induced by pressure overload (in vivo), and in cardiomyocyte hypertrophy evoked by endothelin-1 stimulation (in vitro). Interestingly, the cell size and BNP mRNA expression level (markers of hypertrophy) were greater in cardiomyocytes treated with both neurotrophin-3 and endothelin-1 than in those stimulated with endothelin-1 alone. These findings demonstrate that neurotrophin-3 is a unique hypertrophic factor, which is paradoxically downregulated in cardiac hypertrophy and might counteract hypertrophic change.     

A novel mouse model for MPO-ANCA-associated glomerulonephritis

We established a novel model mouse for myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA)-associated glomerulonephritis with crescentic formation, which was induced by administering bovine serum albumin (BSA). Neutrophil infiltration into the renal glomeruli began at 8 weeks and crescent formation was observed from 10 weeks after the first BSA injection. Platelet and neutrophil counts significantly increased, and proteinuria was observed from 5 weeks. MPO-ANCA increased slightly at 4 and markedly at 9 weeks, and the TNF-alpha level increased at 11 weeks. Glomerular neutrophil infiltration was correlated with MPO-ANCA levels. In addition, proteinuria also significantly correlated with MPO-ANCA levels. Finally, renal crescent formation was associated with an increase of MPO-ANCA levels and neutrophil infiltration into glomeruli. The glomerular immune deposition of IgG and C3 was observed. These findings indicate that BSA induces neutrophil activation of peripheral blood followed by the elevation of MPO-ANCA, resulting in the development of crescentic glomerulonephritis in mice.     

A novel X-linked dominant condition: X-linked congenital isolated ptosis

We present a large family with a previously undescribed condition: X-linked dominant congenital bilateral isolated ptosis. Linkage analysis defined a critical region between Xq24 and Xq27.1, with a maximum single-point LOD score of 2.88 at DXS1047 and DXS984. Male and female family members are equally affected, providing an example of an X-linked, truly dominant condition.     

小鼠心肌肥厚发展过程中心电图动态变化

目的：探讨小鼠心肌肥厚发展过程中心电图的动态变化。方法：复制小鼠压力超负荷性心肌肥厚模型,连续动态监测小鼠从心肌肥厚早期至心力衰竭发展过程中的不同阶段体表心电图改变。结果：①对照组和模型组术后2周内小鼠未见自发性心律失常,而模型组术后5周、9周和13周小鼠出现自发性心律失常,主要表现为频发的室性早搏以及阵发性室性心动过速,心律失常发生率分别为15％、28％和63％。②与同期对照相比,术后2周、5周、9周和13周组动物伽间期以及帆间期明显延长,分别延长20．4％、32．7％、49．7％、61．0％和27．1％、32．1％、43．9％、59．1％（P〈0．01）。③心肌肥厚小鼠心电图的另一个特征为J波变化。所有对照组动物心电图均为正向J波,而模型组动物从2周开始J波正向值下降,5周逐渐变平,到13周时完全翻转。④与同期对照相比,模型组的PR间期没有改变,但术后2周RR问期轻微缩短。结论：心肌肥厚小鼠自发性心律失常发生率逐渐增加,QT间期进行性延长,J波幅值逐渐降低,表明随着疾病的进展心室复极化异常逐渐加重。     

A model for the oxygen-paradox in mouse cardiac muscle

1. Mouse ventricle strips provide a good model system for studying cellular damage in mammalian cardiac muscle. 2. Anoxia rapidly causes destruction of the myofilament apparatus that is characteristic of calcium-triggered damage in muscle cells, and it is suggested that anoxia promotes release of calcium from the mitochondria. 3. Oxygen exacerbates this damage which is independent of extracellular calcium; it is suggested that it initiates myofilament damage by activation at an intracellular site, probably the sarcoplasmic reticulum.     

RNA induction and inheritance of epigenetic cardiac hypertrophy in the mouse

Epigenetic regulation shapes normal and pathological mammalian development and physiology. Our previous work showed that Kit RNAs injected into fertilized mouse eggs can produce heritable epigenetic defects, or paramutations, with relevant loss-of-function pigmentation phenotypes, which affect adult phenotypes in multiple succeeding generations of mice. Here, we illustrate the relevance of paramutation to pathophysiology by injecting fertilized mouse eggs with RNAs targeting Cdk9, a key regulator of cardiac growth. Microinjecting fragments of either the coding region or the related microRNA miR-1 led to high levels of expression of homologous RNA, resulting in an epigenetic defect, cardiac hypertrophy, whose efficient hereditary transmission correlated with the presence of miR-1 in the sperm nucleus. In this case, paramutation increased rather than decreased expression of Cdk9. These results highlight the diversity of RNA-mediated epigenetic effects and may provide a paradigm for clinical cases of familial diseases whose inheritance is not fully explained in Mendelian terms.     

A novel mouse model for invariant NKT cell study

We have generated a novel mouse model harboring the in-frame rearranged TCRValpha specific for invariant NKT (iNKT) cells (Valpha14-Jalpha18) on one allele by crossing the mouse cloned from NKT cells with wild-type mice. This genomic configuration would ensure further rearrangement and expression of TCRValpha14-Jalpha18 under the endogenous promoters and enhancers. Mice harboring such an in-frame rearranged TCRValpha (Valpha14-Jalpha18 mouse) possessed an increase in iNKT cells in the thymus, liver, spleen, and bone marrow. Intriguingly, both Th1- and Th2-type cytokines were produced upon stimulation with alphaGalactosylceramide, an agonist of iNKT cells, and the IgE level in the serum remained unaffected in the Valpha14-Jalpha18 mouse. These features markedly distinguish the nature of iNKT cells present in the Valpha14-Jalpha18 mouse from that of iNKT cells found in the Valpha14-Jalpha18 transgenic mouse. Besides these, the expression of TCRVgammadelta cells remained intact, and the use of the TCRVbeta repertoire in iNKT cells was highly biased to TCRVbeta8 in the Valpha14-Jalpha18 mouse. Furthermore, alphaGalactosylceramide-CD1d dimer-reactive immature iNKT cells expressed less Rag2 as compared with the conventional immature T cells at the positive selection stage. Cell cycle analysis on the thymocytes revealed that no particular subset proliferated more vigorously than the others. Crossing the Valpha14-Jalpha18 mouse with the CD1d knockout mouse revealed a novel population of iNKT cells whose coreceptor expression profile was similar to that assigned to iNKT precursor cells. These mice will be useful for the study on the development of iNKT cells as well as on their functions in the immune system.     

X-linked inhibitor of apoptosis deficiency in the TRAMP mouse prostate cancer model

Deregulation of apoptotic pathways plays a central role in cancer pathogenesis. X-linked inhibitor of apoptosis protein (XIAP), is an antiapoptotic molecule, whose elevated expression has been observed in tumor specimens from patients with prostate carcinoma. Studies in human cancer cell culture models and xenograft tumor models have demonstrated that loss of XIAP sensitizes cancer cells to apoptotic stimuli and abrogates tumor growth. In view of these findings, XIAP represents an attractive antiapoptotic therapeutic target for prostate cancer. To examine the role of XIAP in an immunocompetent mouse cancer model, we have generated transgenic adenocarcinoma of the mouse prostate (TRAMP) mice that lack XIAP. We did not observe a protective effect of Xiap deficiency in TRAMP mice as measured by tumor onset and overall survival. In fact, there was an unexpected trend toward more aggressive disease in the Xiap-deficient mice. These findings suggest that alternative mechanisms of apoptosis resistance are playing a significant oncogenic role in the setting of Xiap deficiency. Our study has implications for XIAP-targeting therapies currently in development. Greater understanding of these mechanisms will aid in combating resistance to XIAP-targeting treatment, in addition to optimizing selection of patients who are most likely to respond to such treatment.     

A multiscale model of cardiac concentric hypertrophy incorporating both mechanical and hormonal drivers of growth

Biomechanics and Modeling in Mechanobiology - Growth and remodeling in the heart is driven by a combination of mechanical and hormonal signals that produce different patterns of growth in response...     

A novel bioluminescence orthotopic mouse model for advanced lung cancer

Lung cancer is the leading cause of cancer-related death in the United States despite recent advances in our understanding of this challenging disease. An animal model for high-throughput screening of therapeutic agents for advanced lung cancer could help promote the development of more successful treatment interventions. To develop our orthotopic lung cancer model, luciferase-expressing A549 cancer cells were injected into the mediastinum of athymic nude mice. To determine whether the model would allow easy monitoring of response to therapeutic interventions, tumors were treated with 30 mg/kg Paclitaxel or were irradiated with 5 fractions of 2 Gy, and tumor burden was monitored using bioluminescence imaging. Evidence of radiation-induced lung injury was assessed using immunohistochemical staining for phospho-Smad2/3 and cleaved caspase-3. We found that tumor implantation recapitulated advanced human lung cancer as evidenced by tumor establishment and proliferation within the mediastinum. The tumor responded to Paclitaxel or radiation as shown by decreased tumor bioluminescence and improved overall survival. Immunohistochemistry revealed increased phospho-Smad2/3 and cleaved caspase-3 in irradiated lungs, consistent with radiation-induced lung injury. This orthotopic lung cancer model may help provide a method to assess therapeutic interventions in a preclinical setting that recapitulates locally advanced lung cancer.     

A novel transgenic mouse model of fetal encephalization and craniofacial development

There are surprisingly few experimental models of neural growthand cranial integration. This, and the dearth of informationregarding fetal brain development, detracts from a mechanisticunderstanding of cranial integration and its relevance to theontogenetic and interspecific patterning of the form of theskull. To address this shortcoming, our research uses transgenicmice expressing a stabilized form of β-catenin to isolatethe effects of encephalization on the development of the basi-and neuro-cranium. These mice develop highly enlarged brainsdue to an increase in neural precursor cells, and differencesbetween transgenic and wild-type mice are predicted to resultsolely from variation in relative brain size. By focusing onprenatal growth, this project adds to our understanding of acritically important period when major structural and functionalinterrelationships are established in the skull. Comparisonsof wild-type and transgenic mice were performed using microcomputedtomography (microCT) and magnetic resonance imaging (MRI). Theseanalyses show that the larger brains of the transgenic miceare associated with a larger neurocranium and an altered basicranialmorphology. However, body size and postcranial ossificationdo not seem to be affected by the transgene. Comparisons ofthe rate of postcranial and cranial ossification also pointto an unexpected effect of neural growth on skull development:increased fetal encephalization may result in a compensatorydecrease in the level of cranial ossification. Therefore, ifother life-history factors are held constant, the ontogeny ofa metabolically costly structure, such as a brain, may occurat the expense of other cranial structures. These analyses indicatethe benefits of a multifactorial approach to cranial integrationusing a mouse model.