AbstractThe present study aimed to screen the best time window for the transplantation of bone marrow mesenchymal stem cells (MSCs) after acute myocardial infarction (MI) through targeted ultrasound microbubbles loaded with SDF-1α antibody. Thirty-six MI miniswine were randomly divided into six experimental groups according to the duration after infarction (1 day, 3 days, 1 week, 2 weeks, 3 weeks, and 4 weeks after infarction). MSCs were labeled with BrdU and then injected through the coronary artery in the stem cell transplantation group to detect the number of transplanted MSCs at different time points after MI. Three miniswine were randomly selected as the control group (sham operation: open chest without ligation of the coronary artery). All SDF-1α groups and control groups were injected with a targeted microbubble ultrasound contrast agent. The values of the myocardial perfusion parameters (A,β, andA×β) were determined.AT,βT, and (A×β)Tvaried with time and peaked 1 week after MI (P< 0.05). The number of transplanted stem cells in the myocardium through coronary injection of MSCs at 1 week was the greatest and consistent with the changing tendency ofAT,βT, and (A×β)T(r= 0.658, 0.778, 0.777,P< 0.05).βT(X), (A×β)T(X), and the number of transplanted stem cells was used to establish the regression equation as follows:Y= 36.11 + 17.601X;Y= 50.023 + 3.348X(R2= 0.605, 0.604,P< 0.05). The best time window for transplanting stem cells was 1 week after MI. The myocardial perfusion parameters of the SDF-1α targeted contrast agent can be used to predict the number of transplanted stem cells in the myocardial tissue.