Effects of blood flow dynamics on autologous pericardial degeneration in reconstructed pulmonary arteries

OBJECTIVES

To clarify the risk factors for abnormal degeneration of autologous pericardium, the mechanical stress on the endothelial tissue caused by turbulent blood flow in the pulmonary artery (PA) reconstructed with autologous pericardium and major aortopulmonary collateral arteries was assumed in pulmonary atresia and ventricular septal defect.

METHODS

Patient-specific PA models were created for 6 patients based on their past computed tomography images taken after unifocalization of major aortopulmonary collateral arteries. Computational fluid dynamics models were created to simulate the physiological pulsatile flow including the peripheral reflection wave, characteristic impedance and autonomous regulation system. Flow streamline, wall shear stress (WSS) and the oscillatory shear index (OSI) were calculated from the simulated result. PA degeneration was evaluated with the computed tomography images before the intracardiac repair.

RESULTS

Regions with physiological high WSS had fewer abnormal changes. Excessively high WSS was often detected at the anastomosis site of the reconstructed PA, and intimal thickening was found in these regions during intracardiac repair. Regions with high OSI and low WSS had dilated change within several months. In 1 patient, in particular, detached vortex flow occurred at the rectangular angle anastomosis site of the right PA in flow streamline, resulting in high OSI and low WSS with abnormal enlargement in the pericardium.

CONCLUSIONS

Endothelial stress caused by blood flow would affect the degeneration of autologous pericardium and major aortopulmonary collateral arteries in the reconstructed PA. High OSI and low WSS might induce enlargement or dilatation, and excessively high WSS in the anastomosis site might induce intimal thickening.

High expression of ABCG2 induced by EZH2 disruption has pivotal roles in MDS pathogenesis

Both proto-oncogenic and tumor-suppressive functions have been reported for enhancer of zeste homolog 2 (EZH2). To investigate the effects of its inactivation, a mutant EZH2 lacking its catalytic domain was prepared (EZH2-dSET). In a mouse bone marrow transplant model, EZH2-dSET expression in bone marrow cells induced a myelodysplastic syndrome (MDS)-like disease in transplanted mice. Analysis of these mice identified Abcg2 as a direct target of EZH2. Intriguingly, Abcg2 expression alone induced the same disease in the transplanted mice, where stemness genes were enriched. Interestingly, ABCG2 expression is specifically high in MDS patients. The present results indicate that ABCG2 de-repression induced by EZH2 mutations have crucial roles in MDS pathogenesis.

Popliteal artery aneurysm treated with implantation of a covered stent graft (fluency(®)) reinforced with a nitinol stent (S.M.A.R.T. (®))

A 60-year-old man was admitted for right knee pain provoked by an enlarging popliteal artery aneurysm (PAA) after endovascular therapy for thromboembolism in the right popliteal artery. The PAA was treated with implantation of a covered stent graft (Fluency(®)); however, acute thromboembolism occurred 6 months after the intervention. Therefore, we implanted a nitinol stent (S.M.A.R.T.(®)) in the proximal part of the covered stent where the major hinge point existed in addition to a stent fracture. No vascular event occurred during 4.5 years of follow-up.

Stent dislodgement induced by a vasodilator used for severe coronary artery spasm caused by Kounis syndrome

Coronary stent dislodgement is a rare but critical complication of percutaneous coronary intervention. It can potentially result in serious consequences, such as stent embolization and emergent coronary artery bypass graft surgery. Here, we describe the successful retrieval of an extracoronary dislodged stent, where dislodgement was induced by a vasodilator used for severe coronary artery spasm caused by Kounis syndrome.

Expressions of local renin-angiotensin system components in chondrocytes

In 2013, we reported that local reninangiotensin system (local RAS) components express during the hypertrophic differentiation of chondrocytes and can modulate it, using ATDC5 cell line that involves differentiation from mesenchymal stem cells to calcified hypertrophic chondrocytes. However, the expressions of local RAS components in normal chondrocytes have not been revealed yet. The purpose of this study is to examine the expression of the local RAS components in chondrocytes in vivo and the conditions allowing the expression. We stained five major regions of 8-week-old C57BL/6 adult mice in which chondrocytes exist, including epiphyseal plates and hyaline cartilages, with antibodies to local RAS components. We also examined the expression of local RAS components in the cultured bovine’s articular cartilage chondrocytes using quantitative reverse transcription polymerase chain reaction and western blot analysis. In result, hypertrophic chondrocytes of epiphyseal plates included in the tibia and the lamina terminals expressed local RAS components. However, hyaline chondrocytes, including the knee articular cartilages, the parenchyma of nasal septums and of the tracheal walls, did not express local RAS components. Cultured bovine’s articular cartilage chondrocytes also did not express local RAS components. However, inducing hypertrophy by administering interleukin-1β or tumor necrosis factor-α, the cultured articular chondrocytes also expressed angiotensin II type 1 receptor and angiotensin II type 2 receptor. In conclusion, local RAS components express particularly in chondrocytes which occur hypertrophy and do not in hyaline chondrocytes. The results are in accord with our previous in vitro study. We think this novel knowledge is important to investigate cartilage hypertrophy and diseases induced by hypertrophic changes like osteoarthritis.

[The treatment strategy for hypoplastic left heart syndrome]

In the recent years, the outcomes of treatment for hypoplastic left heart syndrome (HLHS) is improved because of perioperative management and procedure. We adopt a strategy of the primary Norwood procedure basically for neonates with HLHS, however bilateral pulmonary artery banding precede in patients with risk factors. In the Norwood procedure, aortic arch is reconstructed without artificial prostheses and pulmonary blood flow is supplied from the Blalock-Taussig shunt or the right ventricle-pulmonary artery shunt by case. We administer high dose vasodilators and nitric oxide gas with low resistance strategy after the Norwood procedure. The survival rate of patients with HLHS after 2005 is 84.2% in this strategy.

Downregulation of Dicer expression by serum withdrawal sensitizes human endothelial cells to apoptosis

Although the modulated expression of Dicer is documented upon neoplastic transformation, little is known of the regulation of Dicer expression by environmental stimuli and its roles in the regulation of cellular functions in primary cells. In this study, we found that Dicer expression was downregulated upon serum withdrawal in human umbilical vein endothelial cells (HUVECs). Serum withdrawal induced a time-dependent repression of Dicer expression, which was specifically rescued by vascular endothelial cell growth factor or sphingosine-1-phosphate. When Dicer expression was silenced by short-hairpin RNA against Dicer, the cells were more prone to apoptosis under serum withdrawal, whereas the rate of apoptosis was comparable with control cells in the serum-containing condition. Real-time PCR-based gene expression profiling identified several genes, the expression of which was modulated by Dicer silencing, including adhesion and matrix-related molecules, caspase-3, and nitric oxide synthase 3 (NOS3). Dicer silencing markedly impaired migratory functions without affecting cell adhesion and repressed phosphorylation of focal adhesion kinase and proline-rich tyrosine kinase 2 in adherent HUVECs. Dicer knockdown upregulated caspase-3 and downregulated NOS3 expression, and serum withdrawal indeed increased caspase-3 and decreased NOS3 expression. Furthermore, the overexpression of Dicer in HUVECs resulted in a marked reduction in apoptosis upon serum withdrawal and a decreased caspase-3 and increased NOS3 expression. The inhibition of NOS activity by Nomega-nitro-L-arginine methyl ester abrogated the effect of Dicer overexpression to rescue the cells from serum withdrawal-induced apoptosis. These results indicated that serum withdrawal decreases Dicer expression, leading to an increased susceptibility to apoptosis through the regulation of caspase-3 and NOS3 expression.

MURC, a muscle-restricted coiled-coil protein, is involved in the regulation of skeletal myogenesis

Skeletal myogenesis is a multistep process by which multinucleated mature muscle fibers are formed from undifferentiated, mononucleated myoblasts. However, the molecular mechanisms of skeletal myogenesis have not been fully elucidated. Here, we identified muscle-restricted coiled-coil (MURC) protein as a positive regulator of myogenesis. In skeletal muscle, MURC was localized to the cytoplasm with accumulation in the Z-disc of the sarcomere. In C2C12 myoblasts, MURC expression occurred coincidentally with myogenin expression and preceded sarcomeric myosin expression during differentiation into myotubes. RNA interference (RNAi)-mediated knockdown of MURC impaired differentiation in C2C12 myoblasts, which was accompanied by impaired myogenin expression and ERK activation. Overexpression of MURC in C2C12 myoblasts resulted in the promotion of differentiation with enhanced myogenin expression and ERK activation during differentiation. During injury-induced muscle regeneration, MURC expression increased, and a higher abundance of MURC was observed in immature myofibers compared with mature myofibers. In addition, ERK was activated in regenerating tissue, and ERK activation was detected in MURC-expressing immature myofibers. These findings suggest that MURC is involved in the skeletal myogenesis that results from modulation of myogenin expression and ERK activation. MURC may play pivotal roles in the molecular mechanisms of skeletal myogenic differentiation.

Skeletal muscle-derived progenitors capable of differentiating into cardiomyocytes proliferate through myostatin-independent TGF-beta family signaling

The existence of skeletal muscle-derived stem cells (MDSCs) has been suggested in mammals; however, the signaling pathways controlling MDSC proliferation remain largely unknown. Here we report the isolation of myosphere-derived progenitor cells (MDPCs) that can give rise to beating cardiomyocytes from adult skeletal muscle. We identified that follistatin, an antagonist of TGF-beta family members, was predominantly expressed in MDPCs, whereas myostatin was mainly expressed in myogenic cells and mature skeletal muscle. Although follistatin enhanced the replicative growth of MDPCs through Smad2/3 inactivation and cell cycle progression, disruption of myostatin did not increase the MDPC proliferation. By contrast, inhibition of activin A (ActA) or growth differentiation factor 11 (GDF11) signaling dramatically increased MDPC proliferation via down-regulation of p21 and increases in the levels of cdk2/4 and cyclin D1. Thus, follistatin may be an effective progenitor-enhancing agent neutralizing ActA and GDF11 signaling to regulate the growth of MDPCs in skeletal muscle.

Osteopontin is a myosphere-derived secretory molecule that promotes angiogenic progenitor cell proliferation through the phosphoinositide 3-kinase/Akt pathway

We have reported that skeletal myosphere-derived progenitor cells (MDPCs) can differentiate into vascular cells, and that MDPC transplantation into cardiomyopathic hearts improves cardiac function. However, the autocrine/paracrine molecules and underlying mechanisms responsible for MDPC growth have not yet been determined. To explore the molecules enhancing the proliferation of MDPCs, we performed serial analysis of gene expression and signal sequence trap methods using RNA isolated from MDPCs. We identified osteopontin (OPN), a secretory molecule, as one of most abundant molecules expressed in MDPCs. OPN provided a proliferative effect for MDPCs. MDPCs treated with OPN showed Akt activation, and inhibition of the phosphoinositide 3-kinase (PI3K)/Akt pathway repressed the proliferative effect of OPN. Furthermore, OPN-pretreated MDPCs maintained their differentiation potential into endothelial and vascular smooth muscle cells. These findings indicate an important role of OPN as an autocrine/paracrine molecule in regulating the proliferative growth of muscle-derived angiogenic progenitor cells via the PI3K/Akt pathway.

Stage-specific role of endogenous Smad2 activation in cardiomyogenesis of embryonic stem cells

The role of Smads and their specific ligands during cardiomyogenesis in ES cells was examined. Smad2 was activated bimodally in the early and late phases of cardiac differentiation, whereas Smad1 was activated after the middle phase. Nodal and Cripto were expressed in the early stage and then downregulated, whereas transforming growth factor-beta and activin were expressed only in the late phase. Suppression of early Smad2 activation by SB-431542 produced complete inhibition of endodermal and mesodermal induction but augmented neuroectodermal differentiation, followed by poor cardiomyogenesis, whereas inhibition during the late phase alone promoted cardiomyogenesis. Inhibitory effect of Smad2 on cardiomyogenesis in the late phase was mainly mediated by transforming growth factor-beta, and inhibition of transforming growth factor-beta-mediated Smad2 activation resulted in a greater replicative potential in differentiated cardiac myocytes and enhanced differentiation of nonmyocytes into cardiac myocytes. Thus, endogenous Smad2 activation is indispensable for endodermal and mesodermal induction in the early phase. In the late phase, endogenous transforming growth factor-beta negatively regulates cardiomyogenesis through Smad2 activation by modulating proliferation and differentiation of cardiac myocytes.

Skeletal myosphere-derived progenitor cell transplantation promotes neovascularization in delta-sarcoglycan knockdown cardiomyopathy

Bone marrow cells have been shown to contribute to neovascularization in ischemic hearts, whereas their impaired maturation to restore the delta-sarcoglycan (delta-SG) expression responsible for focal myocardial degeneration limits their utility to treat the pathogenesis of cardiomyopathy. Here, we report the isolation of multipotent progenitor cells from adult skeletal muscle, based on their ability to generate floating-myospheres. Myosphere-derived progenitor cells (MDPCs) are distinguishable from myogenic C2C12 cells and differentiate into vascular smooth muscle cells and mesenchymal progeny. The mutation in the delta-SG has been shown to develop vascular spasm to affect sarcolemma structure causing cardiomyopathy. We originally generated delta-SD knockdown (KD) mice and transplanted MDPCs into the hearts. MDPCs enhanced neoangiogenesis and restored delta-SG expression in impaired vasculatures through trans-differentiation, leading to improvement of cardiac function associated with paracrine effectors secretion. We propose that MDPCs may be the promising progenitor cells in skeletal muscle to treat delta-sarcoglycan complex mutant cardiomyopathy.

MicroRNA-1 facilitates skeletal myogenic differentiation without affecting osteoblastic and adipogenic differentiation

MicroRNAs (miRNAs) are small non-coding RNAs emerging as important post-transcriptional gene regulators. In this study, we examined the role of miR-1, an miRNA specifically expressed in cardiac and skeletal muscle tissue, on the myogenic, osteoblastic, and adipogenic differentiation of C2C12 cells. Upon induction of myogenic differentiation, miR-1 was robustly expressed. Retrovirus-mediated overexpression of miR-1 markedly enhanced expression of muscle creatine kinase, sarcomeric myosin, and alpha-actinin, while the effects on myogenin and MyoD expression were modest. Formation of myotubes was significantly augmented in miR-1-overexpressing cells, indicating miR-1 expression enhanced not only myogenic differentiation but also maturation into myotubes. In contrast, osteoblastic and adipogenic differentiation was not affected by forced expression of miR-1. Thus, the muscle-specific miRNA, miR-1, plays important roles in controlling myogenic differentiation and maturation in lineage-committed cells, rather than functioning in fate determination.

Short-term fluctuations in sinus cycle length after premature ventricular beats in patients with hypertrophic cardiomyopathy and myocardial infarction

BACKGROUND

Sinus cycle length has been reported to fluctuate after a ventricular premature beat (VPB). The purpose of this study was to assess the short-term fluctuations of sinus cycle length in patients with hypertrophic cardiomyopathy (HCM) and prior myocardial infarction (MI).

METHODS

The relative deviation of RR intervals from the mean of the last two RR intervals preceding a VPB were calculated during the 20 subsequent beats following the VPB from Holter recordings in 92 patients with non-obstructive HCM, 57 patients with prior MI and 54 healthy controls.

RESULTS

In controls, the deviations of the RR intervals were negative for several beats after a VPB and subsequently changed to positive before returning to the baseline. Similar changes in RR intervals following a VPB were exhibited in HCM patients; however, the late positive deviations of RR intervals were more marked than in controls. By contrast, in patients with prior MI, the early negative deviations of RR intervals were smaller compared with controls, and the deviations returned to the baseline without incidence of the positive changes.

CONCLUSIONS

Short-term fluctuations in sinus cycle length after a VPB differed exclusively among HCM patients, prior MI patients, and healthy controls.

A case of ST-segment elevation provoked by distended stomach conduit

A case of ST-segment elevation provoked by distended stomach conduit is presented. An 83-year-old woman was admitted to our hospital with worsening chest discomfort. She had a previous history of subtotal esophagectomy, which was reconstructed using a stomach conduit in the posterior mediastinum. Electrocardiogram showed ST-segment elevation in the inferior leads and a prominent negative P wave in lead V1. Echocardiography demonstrated normal left ventricular function without regional wall motion abnormality; however, the left atrium and ventricle compressed by a substantially distended stomach conduit was noted. Subsequent angiocardiography revealed no coronary atherosclerotic stenosis and normal contractility of the left ventricle. Chest symptoms resolved soon after nasogastric suction, leading to resolution of electrocardiographic changes. The stomach conduit diminished on following repeated echocardiography. The patient was discharged without any evidence of myocardial infarction. Esophagus disease of the reconstructed stomach conduit should be recognized as a rare but considerable cause for electrocardiographic changes.

Enhanced vagal modulation and exercise induced ischaemia of the inferoposterior myocardium

OBJECTIVE

To determine whether the Bezold-Jarisch reflex or enhancement of vagal nerves, which are preferentially distributed in the inferoposterior myocardium, results from exercise induced ischaemia in this region.

METHODS

On the basis of exercise myocardial scintigraphy and coronary angiography, 145 patients were classified as follows: group I, 34 patients with inferoposterior ischaemia; group A, 32 with anterior ischaemia; and control, 79 without ischaemia. The relation between ischaemic areas and ECG leads with ST segment changes and vagal modulation assessed by heart rate variability (HRV) (high frequency (HF) component (0.15-0.40 Hz) and coefficient of HF component variance (CCVHF), which is the square root of HF divided by mean RR interval) were assessed.

RESULTS

The rate of ST segment depression in any lead did not differ between group I and group A. HF and CCV(HF) were similar before exercise but higher in group I than in group A and the control group after exercise (mean (SEM) HF: 94 (17) ms2, 41 (7) ms2, and 45 (6) ms2, respectively, p = 0.021; CCV(HF): 1.18 (0.09)%, 0.81 (0.07)%, and 0.89 (0.05)%, p = 0.0053). Furthermore, the percentage change in CCV(HF) before and after exercise was higher in group I than in group A or controls (mean (SEM) 22 (10)%, -24 (4)%, and -21 (3)%, p < 0.0001). The optimal cut off for diagnosis of inferoposterior ischaemia was -5% with a sensitivity of 74%, specificity 75%, and accuracy 75%.

CONCLUSIONS

Vagal modulation as assessed by HRV analysis was enhanced in association with exercise induced inferoposterior ischaemia. Exercise ECG testing combined with HRV analysis would increase accuracy in the diagnosis of ischaemic areas in selected patients with angina pectoris.

Heart rate variability in adult patients with isolated left ventricular noncompaction

BACKGROUND

Isolated left venticular noncompaction (IVNC) is a rare congenital heart disease charactrized by a pattern of an excessively prominent trabecular meshwork with deep intertrabecular recesses. Heart rate variability (HRV) has been reported to be impaired in various heart diseases, though little is known regarding HRV in adult patients with IVNC.

METHODS

We measured spectral components of HRV using fast Fourier transformation of 24-h Holter recordings in 10 adult patients with IVNC, 40 patients with myocardial infarction (MI), 40 patients with hypertrophic cardiomyopathy (HCM) and 40 healthy controls.

RESULTS

The low frequency component and the high frequency component of HRV were lower in IVNC patients tahn those in controls (265 +/- 213 ms(2) vs. 469 +/- 195 ms(2), p < 0.01; 80 +/- 51 ms(2) vs. 185 +/- 126 ms(2), p < 0.01). Furthermore, 3 IVNC patients with a previous history of heart failure exhibited more decreased HRV (low frequency, 75 +/- 56 ms(2); high frequency, 39 +/- 18 ms(2)). Contrary, the ratio of low frequency to high frequency component was higher in patients with IVNC than controls (3.5+/-0.5 vs. 3.2 +/- 0.3, p < 0.05). The degree of impaired HRV was severest in MI patients, intermediate in IVNC patients and mildest in HCM patients compared with controls.

CONCLUSIONS

HRV is impaired in adult patients with IVCN, especially in patients with a previous history of heart failure, suggesting vagal withdrawal or sympathetic enhancement. HRV in IVNC adults is less impaired than in MI patients, and more impaired than in HCM patients of our cohort.

Very low frequency power of heart rate variability is a powerful predictor of clinical prognosis in patients with congestive heart failure

BACKGROUND

The present study examined whether the very low frequency (VLF) power of heart rate variability (HRV) is predictive of clinical prognosis in patients with congestive heart failure (CHF).

METHOD AND RESULTS

The study recruited 54 consecutive CHF patients with emergency admission because of exacerbation of pulmonary congestion. Holter monitoring was performed after improvement of pulmonary congestion. The frequency components of HRV were calculated in the frequency domain (VLF, low frequency (LF), high frequency (HF), total power (TP) and the ratio of LF to HF power). The left ventricular ejection fraction was calculated, and plasma brain natriuretic peptide (BNP) and norepinephrine were also measured at discharge. Within a mean follow-up period of 19.8 +/- 11.7 months, 18 patients experienced cardiovascular events; 7 patients died and 11 patients required rehospitalization because of worsening of CHF. In univariate analysis, diabetes mellitus (DM), BNP and New York Heart Association (NYHA) functional class were significant as risk factors for cardiac events. VLF power, LF power and TP were the strong predictors for cardiac events in HRV. In multivariate analysis, VLF power predicted cardiac events independently of LF power, TP, DM, BNP and NYHA functional class (chi-square=6.24, p=0.01).

CONCLUSIONS

VLF power is an independent risk predictor in patients with CHF.