Augmented Expression of Cardiotrophin-1 and its Receptor Component, gp130, in both Left and Right Ventricles after Myocardial Infarction in the Rat

Cardiotrophin-1 (CT-1) is a potent cytokine that stimulates the assembly of sarcomeric units in series in cardiomyocytes through gp130 signaling, resulting in myocardial cell hypertrophy. To clarify the role of CT-1 and the gp130-signaling pathway during ventricular remodeling after myocardial infarction, we examined the expression of CT-1 and gp130 in a rat model of myocardial infarction. At 1, 3, 7, 14, 28 and 56 days (n=12 for each group) after ligation of a coronary artery, tissue samples were obtained from infarct tissue, the ventricular septum and the right ventricle. All animals developed large myocardial infarctions, with infarct sizes ranging from 39.8% to 50.3%. Progressive left ventricular dilatation and inadequate hypertrophy of the surviving myocardium were confirmed by echocardiography. CT-1 and gp130 mRNA levels were determined by semiquantitative reverse transcription-polymerase chain reaction using 1 or 5 μ g of total RNA followed by Southern blotting. The densitometric analysis of the Southern blots revealed a significant increase in CT-1 and gp130 mRNA levels (P<0.01) compared with those of the sham-operated rats at 1, 3, 7, 14, 28 and 56 days post-infarct in the infarct area, the ventricular septum (non-infarcted area) and right ventricle. The protein levels of CT-1 and gp130, determined by Western blot analysis, were significantly increased (P<0.05) compared with those of sham-operated rats, peaked during the acute stage and declined thereafter in the three regions described above. Immunohistochemical staining showed that CT-1 and gp130-immunoreactivities were detected in cardiomyocytes and fibroblast-like cells and that the intensity of staining was increased at 7 days post-infarct compared with that in sham-operated rats. An augmented CT-1 and gp130 system thus appears to play an important role during ventricular remodeling after myocardial infarction.