Trials investigating the role of mesenchymal stem cells (MSCs) in increasing ejection fraction (LVEF) after acute myocardial infarction (AMI) have raised some controversies. This study was conducted to find whether transplantation of MSCs after AMI can help improve myocardial performance indices or clinical outcomes.
Randomized trials which evaluated transplantation of MSCs after AMI were enrolled. The primary outcome was LVEF change. We also assessed the role of cell origin, cell number, transplantation time interval after AMI, and route of cell delivery on the primary outcome.
Thirteen trials including 956 patients (468 and 488 in the intervention and control arms) were enrolled. After excluding the biased data, LVEF was significantly increased compared to the baseline among those who received MSC (WMD = 3.78%, 95% CI: 2.14 to 5.42, p < 0.001, I2 = 90.2%) with more pronounced effect if the transplantation occurred within the first week after AMI (MD = 5.74%, 95%CI: 4.297 to 7.183; I2 = 79.2% p < 0.001). The efficacy of trans-endocardial injection was similar to that of intracoronary infusion (4% [95%CI: 2.741 to 5.259, p < 0.001] vs. 3.565% [95%CI: 1.912 to 5.218, p < 0.001], respectively). MSC doses of lower and higher than 107 cells did not improve LVEF differently (5.24% [95%CI: 2.06 to 8.82, p = 0.001] vs. 3.19% [95%CI: 0.17 to 6.12, p = 0.04], respectively).
Transplantation of MSCs after AMI significantly increases LVEF, showing a higher efficacy if done in the first week. Further clinical studies should be conducted to investigate long-term clinical outcomes such as heart failure and cardiovascular mortality.