The aim of the present study was to investigate the changes in absolute myocardial blood flow (AMF) after intracoronary injections of mesenchymal SC (MSC) and compared to controls in closed-chest reperfused acute myocardial infarction (AMI) in pigs. Male MSCs, transiently transfected with Luciferase (Luc-MSC) were delivered (9.7 ± 1.2 x 10(6)) intracoronary in the open infarct-related artery one-week post-AMI in female pigs (group MSC), while saline was injected with the same injection rate in controls (group C). The AMF was measured immediately after, and 3, 12 and 24 h post-intracoronary Luc-MSC or saline injections. In vitro bioluminescence images and quantitative real-time TaqMan PCR measurements were performed to quantify the sex-mismatched MSCs. No difference between the groups was observed regarding the weight, heart rate, blood pressure and global ejection fraction 1-week post-AMI. The baseline AMF were similar in the groups (61.3¿±¿15. vs 61.1¿±¿12.0 ml/min). AMF was decreased significantly immediately after intracoronary MSC delivery (42.0¿±¿12.4 vs 57.7¿±¿15.7 ml/min p¿=¿0.013), and remained low at 3 h (40.9¿±¿13.4 vs 55.8¿±¿4.9 ml/min, p¿=¿0.004), 12 h (43.0¿±¿3.7 vs 57.8¿±¿5.4 ml/min, p¿=¿0.001) with incomplete recovery at 24 h (47.2¿±¿5.5 vs 62.1¿±¿14.1 ml/min, p¿=¿0.038) as compared to controls, respectively. In vitro bioluminescence displayed transfected Luc-MSCs along the proximal and mid part of the LAD, with limited number (295¿±¿101 sry copied/million cardiac cells) of Y-chromosome-MSCs in the infarcted area. Intracoronary injection of SCs results in immediate decrease of AMF, with delayed recovery. The delivery of the SC into the injured myocardium might be hindered by the altered coronary pressure and flow conditions.

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