Abstract:

BACKGROUND: The previous studies showed that intra-coronary or intra-myocadial intransplantation of human umbilical cord blood mononuclear cells (HUCBC) could promote angiogenesis, and reduce myocardial infarcted area associated with improvement of cardiac function. But, there is no study about the effect of human umbilical cord blood cells on cardiomyocyte apoptosis.
OBJECTIVE: To observe the effects of intravenous administration of HUCBC on cardiomyocyte apoptosis and the expressions of Bcl-2 and Bax proteins after acute myocardial infarction (AMI).
METHODS：A total of 45 adult rabbits were divided into three groups randomly: transplantation group with 15 rabbits was intravenously administrated with 500 μL HUCBC labeled with 2×107 bromodexyuridine (BrdU) at 24 hours after AMI: control group with 15 rabbits was intravenously administrated with 500 μL saline at 24 hours after AMI；sham operation group with 15 rabbits, not receiving ligation of left anterior descending branch, was intravenously administrated with 500 μL saline at 24 hours after operation. Cardiac functions were performed by echocardiography at 1, 2 and 4 weeks after transplantation. Myocardial tissue sections were observed using hematoxylin-eosin staining to measure pathological changes in myocardium at 4 weeks following transplantation. The apoptotic cells were detected in the myocardium by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). BrdU-positive cells and the expression of Bcl-2 and Bax proteins were identified in the myocardium by immunohistochemical method.
RESULTS AND CONCLUSION: ①Compared with control group, cardiac functions were significantly improved in the transplantation group. ②BrdU-positive cells were found surrounding infarct site in the transplantation group. ③Compared with the control group, Bcl-2 protein levels were significantly increased, but Bax protein levels were significantly decreased in the transplantation group. ④Number of apoptotic cardiomyocytes was significantly less in the transplantation group than the control group at 4 weeks following transplantation. These verified that HUCBCs by intravenous administration migrate into the peri-infarcted area, and regulate the expression of Bcl-2 and Bax proteins, and inhibit cardiomyocyte apoptosis in the peri-infarcted area, and finally improve cardiac function following myocardial infarction.