Takeshi Nishina

Upregulation of SR-PSOX/CXCL16 and Recruitment of CD8+ T Cells in Cardiac Valves During Inflammatory Valvular Heart Disease

Objective—SR-PSOX/CXCL16 is a transmembrane chemokine and is implicated in activated CD8+ T cell trafficking. In the present study, we examined the expression pattern of SR-PSOX/CXCL16 in the heart and investigated a potential role of SR-PSOX/CXCL16 in inflammatory valvular heart disease. Methods and Results—Initial expression of SR-PSOX/CXCL16 in murine embryos was detected in endothelial cells lining endocardial cushions in the forming heart at E11.5. From mid-gestation to adult, expression of this gene in the heart was exclusively observed in valvular endothelial cells. Examination of SR-PSOX/CXCL16 expression in human cardiac valves demonstrated that SR-PSOX/CXCL16 was strongly expressed in valvular and neocapillary endothelial cells in patients with infective endocarditis. SR-PSOX/CXCL16 expression in neocapillary endothelial cells was also observed in patients with rheumatic and atherosclerotic valvular disease. Moreover, CD8+ T cells were distributed closely to endothelial cells expressing SR-PSOX/CXCL16. In vitro adhesion assays showed that SR-PSOX/CXCL16 induced adhesion of activated CD8+ T cells to vascular cell adhesion molecule-1 (VCAM-1) through very late antigen-4 (VLA-4) activation. Furthermore, SR-PSOX/CXCL16 stimulated interferon-&ggr; (IFN-&ggr;) production by CD8+ T cells. Conclusions—SR-PSOX/CXCL16 may be involved in CD8+ T cell recruitment through VLA-4 activation and stimulation of IFN-&ggr; production by CD8+ T cells during inflammatory valvular heart disease.

Chymase inhibition prevents cardiac fibrosis and dysfunction after myocardial infarction in rats

Human chymase activates not only angiotensin II but also transforming growth factor-β, a major stimulator of myocardial fibrosis, while rat chymase activates transforming growth factor-β, but not angiotensin II. To clarify the role of chymase-dependent transforming growth factor-β activation, we evaluated whether chymase inhibition prevents cardiac fibrosis and cardiac dysfunction after myocardial infarction in rats. Myocardial infarction was induced by ligation of the left anterior descending coronary artery. One day after the ligation, rats were randomized into 2 groups: 1) a chymase-treated group that received 10 mg/kg per day of the chymase inhibitor NK3201 orally for 4 weeks; and 2) a vehicle group of non-treated rats with myocardial infarction. We also included a control group who underwent sham-operation and no treatment. Four weeks after ligation, echocardiography revealed that chymase inhibitor treatment reduced the akinetic area and increased fractional area change but did not significantly change left ventricular end-diastolic area. Chymase inhibition significantly reduced left ventricular end-diastolic pressure, increased the maximal end-systolic pressure–volume relationship and decreased the time constant of left ventricular relaxation. Chymase activity in the non-infarcted myocardium was significantly increased in the vehicle group, but it was significantly reduced by chymase inhibitor treatment. The fibrotic area in the cardiac tissues and the mRNA levels of collagen I and collagen III were also significantly lower in the chymase inhibitor-treated group than in the vehicle group. Therefore, the pathway forming chymase-dependent transforming growth factor-β may play an important role in myocardial fibrosis and cardiac dysfunction rather than left ventricular dilatation after myocardial infarction.

Atrial Natriuretic Peptide Helps Prevent Late Remodeling After Left Ventricular Aneurysm Repair

Background—Left ventricular aneurysm repair (LVR) reduces LV wall stress and improves LV function. However, as we reported previously, the initial improvement of LVR was short-term because of LV remodeling but could be maintained longer with postoperative use of an angiotensin-converting enzyme (ACE) inhibitor. Atrial natriuretic peptide (ANP) has been used to treat patients with heart failure by natriuretic and vasodilatory actions. Recent reports have suggested that ANP inhibits the rennin-angiotensin system. In this study, the effects of ANP after LVR were evaluated. Methods and Results—Rats that had an LV aneurysm 4 weeks after left anterior descending artery ligation underwent LVR by plicating the LV aneurysm and were randomized into 2 groups: LVR+A group was intravenously administrated with 10 &mgr;g/h of carperitide, recombinant &agr;-hANP, by osmotic-pump for 4 weeks, and the LVR group was given normal saline. Echocardiography revealed better LV remodeling and function in LVR+A group than in LVR group. Four weeks after LVR, left ventricular end diastolic pressure (LVEDP) and Tau were significantly lower in LVR+A group (LVEDP: 10±4 in LVR+A group versus 18±6 mm Hg in LVR group, Tau: 13±2 versus 17±2ms). End-systolic elastance (Ees) was higher in LVR+A group (Ees: 0.34±0.2 versus 0.19±0.11 mm Hg/&mgr;L). The levels of myocardial ACE activity in LVR+A group was significantly lower than in LVR group. The mRNA expressions of brain natriuretic peptide and transforming growth factor &bgr;1 inducing fibrosis significantly decreased in LV myocardium in LVR+A group. Histologically, myocardial fibrosis was significantly reduced in LVR+A group. Conclusions—Intravenous administration of ANP had beneficial effects on LV remodeling, function, and fibrosis after LVR. ANP could be a useful intravenous infusion drug for postoperative management after LV repair surgery.

PMEA coating of pump circuit and oxygenator may attenuate the early systemic inflammatory response in cardiopulmonary bypass surgery.

We investigated the effects of coating a cardiopulmonary bypass (CPB) circuit and oxygenator with poly-2-methoxy-ethyl acrylate (PMEA) on the systemic inflammatory response during and after CPB. Thirty patients undergoing elective cardiac surgery were randomized into three groups (each group n = 10): noncoated (group N), heparin coated (group H), and PMEA coated circuit and oxygenator (group X). Bradykinin (BK), complement 3 activation (C3a) and interleukin-6 (IL-6) levels were measured as early phase indicators of inflammatory response, as were maximum C reactive proteins (CRP) and white blood cell (WBC) levels. The alveolar–arterial oxygen gradient (A-a DO2) was measured as a parameter of respiratory function. IL-6 levels after CPB were significantly higher in group N than in groups H and X (p < 0.05). Serum BK and C3a levels showed similar patterns in all groups. A-a DO2 was lower at the end of and 3 hours after CPB in groups H and X than in group N (p < 0.05). Maximum CRP levels were lower in group X than in groups N (p < 0.05). This prospective study suggests that PMEA coated CPB may improve respiratory function and decrease systemic inflammatory response after cardiac surgery, possibly because this circuit is as biocompatible as heparin coated CPB circuit.

Cardiomyocyte transplantation does not reverse cardiac remodeling in rats with chronic myocardial infarction

BACKGROUND Several reports have documented the potential benefits of cell transplantation as an alternative to cardiac transplantation. This study was designed to investigate whether cardiomyocyte transplantation is effective in rats with chronic myocardial infarction. METHODS Syngeneic Lewis rats were used in this study. Chronic myocardial infarction was induced in rats by ligating the left anterior descending artery. Four weeks later, after left ventricular (LV) dysfunction with akinetic regions was confirmed by echocardiography, the rats were randomized into two groups: a group that received fetal cardiomyocyte transplantation (TX group; n = 11); and a group that received an intramyocardial injection of culture medium only (control group; n = 12). RESULTS Four weeks after treatment, the TX group had smaller end-systolic dimension (LVDs) (7.5 +/- 0.9 vs 8.9 +/- 0.8 mm, p < 0.01) and better fractional shortening (FS) (26.2 +/- 5.9 vs 17.7% +/- 5.1%, p < 0.01) than the control group. However, there were no differences in LV end-diastolic dimension, LVDs, and FS between baseline and post-treatment values in the TX group. In addition, plasma levels of atrial natriuretic peptide were not significantly different between the two groups 4 weeks after treatment. In microscopic examination, small amounts of transplanted cardiomyocytes were found only in the periinfarct area, not in the center of scar area, and a thicker ventricular wall in the infarct area was detected in the TX group. CONCLUSIONS Fetal cardiomyocyte transplantation prevented, but did not reverse, cardiac remodeling that was accompanied with heart failure in myocardial infarction rats. Further investigation is warranted for optimal clinical application to the failing heart.

Impact of left atrial volume reduction concomitant with atrial fibrillation surgery on left atrial geometry and mechanical function

OBJECTIVE Left atrial geometry and mechanical functions exert a profound effect on left ventricular filling and overall cardiovascular performance. We sought to investigate the perioperative factors that influence left atrial geometry and mechanical functions after the Maze procedure in patients with refractory atrial fibrillation and left atrial enlargement. METHODS Seventy-four patients with atrial fibrillation and left atrial enlargement (diameter > or = 60 mm) underwent the Maze procedure in association with mitral valve surgery. The maximum left atrial volume and left atrial mechanical functions (booster pump, reservoir, and conduit function [%]) were calculated from the left atrial volume-cardiac cycle curves obtained by magnetic resonance imaging. A stepwise multiple regression analysis was performed to determine the independent variables that influenced the postoperative left atrial geometry and function. RESULTS The multivariate analysis showed that left atrial reduction surgery concomitant with the Maze procedure and the postoperative maintenance of sinus rhythm were predominant independent variables for postoperative left atrial geometry and mechanical functions. Among the 58 patients who recovered sinus rhythm, the postoperative left atrial geometry and function were compared between patients with (VR group) and without (control group) left atrial volume reduction. At a mean follow-up period of 13.8 months, sinus rhythm recovery rate was better (85% vs 68%, P < .05) in the VR group and maximum left atrial volume was less (116 +/- 25 mL vs 287 +/- 73 mL, P < .001) than in the control group. The maximum left atrial volume reduced with time only in the VR group (reverse remodeling). Postoperative booster pump and reservoir function in the VR group were better than in the control group (25% +/- 6% vs 11% +/- 4% and 34% +/- 7% vs 16% +/- 4%, respectively, P < .001), whereas the conduit function in the VR group was lower than in the control group, indicating that the improvement of the booster pump and reservoir function compensated for the conduit function to left ventricular filling. CONCLUSION Left atrial reduction concomitant with the Maze procedure helped restore both contraction (booster pump) and compliance (reservoir) of the left atrium and facilitated left atrial reverse remolding. Left atrial volume reduction and postoperative maintenance of sinus rhythm may be desirable in patients with refractory AF and left atrial enlargement.

Does the β2-Agonist Clenbuterol Help to Maintain Myocardial Potential to Recover During Mechanical Unloading?

Objective—Chronic mechanical unloading induces left ventricular (LV) atrophy, which may impair functional recovery during support with an LV-assist device. Clenbuterol, a β2-adrenergic receptor (AR) agonist, is known to induce myocardial hypertrophy and might prevent LV atrophy during LV unloading. Furthermore, β2-AR stimulation is reported to improve Ca2+ handling and contribute to antiapoptosis. However, there is little information on the effects of clenbuterol during LV unloading. Methods and Results—We investigated LV atrophy and function after LV unloading produced by heterotopic heart transplantation in isogenic rats. After transplantation, rats were randomized to 1o f 2 groups (n=10 each). The clenbuterol group received 2 mg·kg−1·d−1 of the drug for 2 weeks; the control group received normal saline. The weight of unloaded control hearts was 48% less than that of host hearts after 2 weeks of unloading. Clenbuterol significantly increased the weight of the host hearts but did not prevent unloading-induced LV atrophy. Papillary muscles were isolated and stimulated, and there was no difference in developed tension between the 2 groups. However, the inotropic response to the β-AR agonist isoproterenol significantly improved in the clenbuterol group. The mRNA expression of myocardial sarco(endo)plasmic reticulum Ca2+-ATPase 2a (SERCA2a) and fetal gene shift (myosin heavy chain [MHC] mRNA isozyme) was also significantly improved by clenbuterol treatment. There was no difference in β1-AR mRNA expression between the 2 groups. In contrast, β2-AR mRNA was significantly decreased in the clenbuterol-treated, unloaded heart. This indicates that clenbuterol may downregulate β2-ARs. In the evaluation of apoptosis, mRNA expression of caspase-3, which is the central pathway for apoptosis, tended to be better in the clenbuterol group. Conclusions—During complete LV unloading, clenbuterol did not prevent myocardial atrophy but improved gene expression (SERCA2a, β-MHC) and β-adrenergic responsiveness and potentially prevented myocardial apoptosis. However, chronic administration of clenbuterol may be associated with downregulation of β2-ARs.

Visualization of intramuscular left anterior descending coronary arteries during off-pump bypass surgery

In off-pump coronary artery bypass surgery, an appropriate method for intraoperative evaluation of grafts and vessels has been awaited. We report the usefulness of a 15-MHz linear transducer for this purpose. A 15-MHz linear transducer with a SONOS 5500 (Philips Medical Systems, Best, Netherlands) was applied epicardially in off-pump coronary artery bypass surgery patients. Vascular anatomy was easily discerned when the transducer was applied in an appropriate way. In 6 patients, intramuscular coronary arteries were easily detected, and in all of these patients, anastomoses were successful. The shapes of the anastomoses were very clearly shown, and the flow and its phase in the bypass graft or coronary artery were measured with synchronization of electrocardiograms in all patients. The total left internal thoracic artery (LITA) flow (28.4 +/- 6.8 mL/s) and the pattern of the flow was dominantly diastolic in all patients. The 15-MHz linear transducer system (Philips) is very useful for detecting intramuscular left anterior descending coronary arteries and may become one of the standard tools for intraoperative evaluation in off-pump coronary artery bypass surgery.

Effect of edaravone, a novel free radical scavenger, supplemented to cardioplegia on myocardial function after cardioplegic arrest: in vitro study of isolated rat heart

Cardioplegic arrest has been the main mechanism of myocardial protection during open-heart surgery; however, it causes myocardial injury during ischemia-reperfusion. Free radical scavengers are widely known to attenuate ischemia-reperfusion injury in various settings. We investigated the effects of edaravone, a novel free radical scavenger that was originally used for cerebral protection, on myocardial function during ischemia-reperfusion after cardioplegic arrest. Rat hearts were excised and perfused using Langendorff apparatus. The hearts were cardioplegically arrested for 90 min using St. Thomas’ Hospital cardioplegic solution (ST solution) at 4°C every 45 min and then reperfused for 20 min. The hearts were divided into 4 groups (n = 13 in each group). In Group ST, the hearts were arrested using the ST solution alone. In Groups L, M, and H, the hearts were arrested using the ST solution supplemented with a low-dose (1 μM), moderate dose (10 μM), and high dose (100 μM) of edaravone, respectively. Left ventricular function (+dp/dtmax) and the levels of the cardiac enzymes released were measured before and after cardioplegic arrest. At the end of the study, the water content and the tissue oxidative stress (8-hydroxy-2′-deoxyguanosine) of the heart were measured. During reperfusion, the edaravone-treated groups showed a greater functional recovery with regard to the +dp/dtmax (P < 0.05). The lactate level was the lowest (P < 0.01) in Group M. The water content of the hearts in the edaravone-treated groups was significantly lower (P < 0.05) than that in Group ST. Oxidative stress was significantly lower (P < 0.01) in the edaravone-treated hearts than in Group ST, and it was the lowest in Group M. The addition of edaravone to the cardioplegic solution ameliorates the impairment in myocardial function by reducing the oxidative stress after cardioplegic arrest. In this study, the maximum improvement in the myocardial function was achieved by addition of a moderate dose (10 μM) of edaravone.

Results of Chronic Animal Experiments With a New Version of a Magnetically Suspended Centrifugal Pump

We have developed a magnetically suspended centrifugal pump (MSCP) for long-term ventricular support. This study reports results of chronic animal experiments using a new version of the MSCP. Three sheep weighing 50-70 kg were used in this study. A left heart assist system was established with cannulas into the descending aorta and the left ventricular apex. In two sheep the MSCP was positioned outside the body and in one sheep implanted on the chest wall. The pumping flow was estimated by the motor current and motor speed. The temperature of the pump and the muscle near the pump was recorded for 10 days after operation. The duration of continuous pumping was 60, 140, and 230 days+ (ongoing), respectively. The cause of termination was infection associated with thrombus formation in the first, and failure of magnetic suspension in the second sheep. No thrombus or embolus was observed after sacrifice of the second sheep. The third sheep has been going well despite skin necrosis around the pump pocket. The estimation of pumping flow was reliable even at 140 days. Temperature of the pump surface was 42 degrees C immediately after the operation and gradually reduced to 41 degrees C. The MSCP is a reliable pump for long-term circulatory assist.