Formation of cell junctions between grafted and host cardiomyocytes at the border zone of rat myocardial infarction

BACKGROUND

Cardiomyocyte transplantation is an innovative strategy for the treatment of heart failure after myocardial infarction. Cell junctions show diverse temporal polarization toward intercalated disks during postnatal development and exhibit altered distribution in diseased hearts. To elucidate the formation of cell junctions between grafted and host cardiomyocytes at the border zone of myocardial infarction, the 3D distribution of cell junctions was examined using immunohistochemistry and confocal microscopy.

METHODS AND RESULTS

Neonatal cardiomyocytes obtained from 3-day-old rats by collagenase digestion and Percoll density centrifugation were injected into the border zones of infarction sites 10 days after coronary ligation in adult rats. At 4 to 14 days after transplantation, hearts were harvested and processed by immunohistochemistry. Antibodies against connexin43, desmoplakin, and cadherin were used to analyze the distribution of gap junctions, desmosomes, and adherens junctions, respectively. Grafted cardiomyocytes were identified by immunohistochemistry for alpha-smooth muscle actin. Grafted cardiomyocytes tended to align parallel to the host cardiomyocytes. Connexin43, desmoplakin, and cadherin were localized between grafted cardiomyocytes themselves and between grafted and host cardiomyocytes. Semiquantitative analysis revealed that all junctions showed increasing polarization to longitudinal cell termini, especially at the border of grafted and host cardiomyocytes, as time advanced from 4 to 7 days after transplantation.

CONCLUSIONS

These findings indicate that grafted cardiomyocytes foster electrical pathways with host counterparts through the gap junction and suggest that the environment in infarcted hearts could influence the localization of gap junctions, desmosomes, and adherens junctions.

Transposition of the great arteries with anomalous origin of the left coronary artery from the pulmonary artery

We describe an extremely rare case of successful arterial switch operation for an infantile complete transposition of the great arteries associated with ventricular septal defect and anomalous origin of the left coronary artery from the pulmonary artery in which the left main coronary artery arose from the posterior sinus of the pulmonary artery and the right coronary artery and an accessory branch arose from the aorta.

[Clinical problems in surgical treatment for active infective endocarditis]

From October, 1982, to December, 1995, 22 patients with active infective endocarditis underwent surgical treatment. Of 22 patients, 12 patients (group P) demonstrated microorganisms on blood culture obtained at the operation and/or in the excised valve, and 10 patients (group N) showed acute inflammatory reaction in the excised valve microscopically. Operative mortality in group P was significantly higher than that in group N (50% versus 0%,p < 0.01). Especially in group P, five of six patients (83%) with uncontorolled infection for more than eight days died within 30 days of operation. This showed that prolonged preoperative periods of uncontrolled infection influenced the surgical outcome of active infective endocarditis. In conclusion, patients who do not promptly response to antibiotic treatment must be considered for early operation within seven days of the diagnosis of infective endocarditis to decrease operative mortality. The plasma level of CRP and definition of sepsis may be useful as indicators of uncontrolled infection.

[Surgical treatment for ascending aortic aneurysm using a transthoracic left ventricular venting]

Three patients with ascending aortic aneurysms underwent graft replacement using deep hypothermic circulatory arrest with continuous retrograde cerebral perfusion. In all three cases, preoperative radiographic examination revealed that the aneurysm was large, thin, and adherent to the back of the sternum. For this reason, left ventricular venting was performed through a left thoracotomy before median sternotomy, to decrease both the risk of rupture of the aneurysm and the difficulty of cannulation. This new method, called transthoracic left ventricular venting, was very useful for performing a median sternotomy under hypotensive and hypothermic conditions adequate to reduce the risk of rupture and to manage any rupture immediately through deep hypothermic circulatory arrest.

[A successful correction of common atrium with left atrial isomerism]

A successfully treated case of one-year-old girl of common atrium associated with bilateral superior vena cava and an interrupted inferior vena cava with hemiazygos continuation is reported. In addition to these anomalies of systemic venous connection, both atrial appendages show morphological characteristics of left type, and the final diagnosis of left atrial isomerism was made. In the corrective surgery, atrial septation was reconstructed using trimmed autogenous pericardial patch to allow the left superior vena cava to drain into the right side of the common atrium. The patient had been pointed out bradycardia (50-100/min) since her birth. Postoperative electrocardiogram also showed bradycardia (78-100/min). Especially in sleeping, her heart rate was 50-60/min, resulting in A-V junctional escaped rhythm and A-V dissociation. This fact suggests that her sinus node is absent or hypoplastic, one of the characteristics of left atrial isomerism. Since left atrial isomerism is reported to cause a decrease of atrial rhythm with aging, careful postoperative observation on specific arrhythmia is necessary.