2.1 Search results
The initial search identified 481 articles (Pubmed=91; Embase databases=263; The Cochrane Library=127), of which 464 references were excluded because of duplication, reviews, reviews, animal experiments, and inconsistent research content. Then, 17 articles were read in full, and 10 articles were finally included, of which 1 article [18] was excluded because of statistical contradictions in the LVEF baseline data. Finally, 9 articles with 460 patients were included. A flow diagram depicting studies selection process is demonstrated in Fig. 1.
2.2 Characteristics and quality of included studies
In total, 460 patients with AMI (MSCs group 240, control group 220) from 9 RCT were available for the final meta-analysis. Publication years were from 2004 to 2021. Follow-up duration was from 3 to 24 months. MSC was infused into intracoronary (7 studies) [9] [10] [19] [20] [21] [22] [23] and intravascular (2 studies) [24] [25] routes. Total injected cell doses ranged from <107 to >108, and infusion time after PCI was between less than 2 days and 2 weeks later. The origin of MSCs were bone marrow (7 studies) [19] [24] [20] [21] [25] [22] [23], adipose tissue (1 study) [9], and umbilical cords (1 study) [10]. The main characteristics of each individual study are summarized in Table 1 and Table 2. The methodological quality of the enrolled studies was assessed using RevMan 5.3 as shown in Fig. 2 and Fig. 3.
TABLE1. Basic characteristics of involved studies
Author, year
|
Country
|
Sample size n(T/C)
|
Age (T/C years)
|
Study design
|
Setting
|
Population
|
Chen et al., 2004[19]
|
China
|
69(34/35)
|
58±7/57±5
|
RCT
|
Single-center
|
AMI
|
Hare et al., 2009[24]
|
USA
|
60(39/21)
|
59.0±12.3/55.1±10.2
|
RCT
|
multi-center (10)
|
AMI
|
Houtgraaf et al., 2012[9]
|
Netherlands
|
14(10/4)
|
61±2.1/55±7.5
|
RCT
|
Single-center
|
AMI
|
Gao et al., 2013[20]
|
China
|
43(21/22)
|
55.0±1.6/58.6±2.5
|
RCT
|
multi-center (4)
|
AMI
|
Lee et al., 2014[21]
|
South Korea
|
69(33/36)
|
53.9±10.5/54.2±7.7
|
RCT
|
multi-center (3)
|
AMI
|
Gao et al., 2015[10]
|
China
|
116(58/58)
|
56.7±1.7/57.3±1.3
|
RCT
|
multi-center (11)
|
AMI
|
Chullikana et al.,2015[25]
|
India
|
20(10/10)
|
47.31±12.10/47.79±6.48
|
RCT
|
multi-center (4)
|
AMI
|
kim SH et al., 2018[22]
|
South Korea
|
26(14/12)
|
57.8±8.9/55.3±8.6
|
RCT
|
Single-center
|
AMI
|
Zhang et al., 2021[23]
|
China
|
43(21/22)
|
59.3±9/58.6±11
|
RCT
|
multi-center (6)
|
AMI
|
Note: RCT randomized controlled trail; AMI acute myocardial infarction.
TABLE 2. Procedural characteristics of involved studies
Author, year
|
Cell type
|
Cell dose
|
Time of cell therapy
(post-PCI)
|
Route of delivery
|
Follow-up (months)
|
Endpoint
|
Chen et al., 2004[19]
|
Autologous
BM-MSCs
|
8-10×10^9
|
18.4±0.5 days
|
IC
|
3, 6
|
①
|
Hare et al., 2009[24]
|
Unmatched allogeneic
BM-MSCs
|
0.5,1.6,5×10^6
|
Randomized 1-10 days
|
IV
|
3, 6, 12
|
①②③
|
Houtgraaf et al., 2012[9]
|
Autologous
ADRCs
|
1.74±0.41×10^7
|
24 hours
|
IC
|
6
|
①
|
Gao et al., 2013[20]
|
Autologous
BM-MSCs
|
3.08±0.52×10^6
|
17±1 days
|
IC
|
6, 12, 24
|
①②③
|
Lee et al., 2014[21]
|
Autologous
BM-MSCs
|
7.2 ± 0.90×10^7
|
25±2.4 days
|
IC
|
6
|
①②③
|
Gao et al., 2015[10]
|
Unmatched allogeneic
WJ-MSCs
|
2 × 10^8
|
5-7 days
|
IC
|
4,12,18
|
①②③
|
Chullikana et al.,2015[25]
|
Unmatched allogeneic
BM-MSCs
|
2×10^6/kg
|
2 days
|
IV
|
6, 24
|
①
|
kim SH et al., 2018[22]
|
Autologous
BM-MSCs
|
7.2 ± 0.90×10^7
|
30±1.3 days
|
IC
|
4,12
|
① ②③
|
Zhang et al., 2021[23]
|
Autologous
BM-MSCs
|
3.31±1.7× 10^6
|
14.07±9.53 days
|
IC
|
6,12
|
① ②③
|
Note: BM-MSCs bone marrow mesenchymal stem cells; ADRCs Adipose Tissue-Derived Regenerative Cells; WJ-MSCs Wharton’s jelly–derived mesenchymal stem cells; IC intracoronary; IV intravascular; ① LVEF; ② LVESV; ③ LVEDV.
2.3 Overall effects of MSCs therapy on LVFE
The 9 studies included in present meta-analysis were tested for heterogeneity, I2=89%>50%, and the Q-test P<0.1, suggesting that there was high degree of heterogeneity between these studies. Therefore, we can choose a random effects model to summarize the data, or conduct a sensitivity analysis to confirm the statistical power of the study and seek out the heterogeneity sources (Fig. 4). Base on the random effects model, the results of our analysis indicated that overall LVEF is increased by 3.08% (95% CI, 1.81to 4.35; P <0.00001) compared to the control group (Fig. 5a). The initial result did not change when we removed the studies one by one. However, we observed that, when ignoring the studies by Chen et al., 2004[19] and Gao et al., 2013[20], the I2 value changed from 89% to 0% (Fig. 5b). Therefore, we hypothesize that the two studies may be sources of heterogeneity. After ignoring the two studies, injection of MSCs improved LVEF by 3.13 (95% CI, 2.85 to 3.41; P<0.00001; I2 =0%). We highly suspect that the source of the heterogeneity was the follow-up time, the dose and timing of stem cell transplantation, and subsequent subgroup analysis was conducted. The funnel plots was used to investigate whether there was publication bias in this study (Fig. 6). The basic symmetry of the funnel plots means that there was no publication bias. Using the Stata 15.1 to perform the begg test, P = 0.917>0.05, and the egger test, P = 0.837>0.05, which means that there was no publication bias in the 9 articles included in this study.
2.4 Effects of MSCs therapy on LVFE over time
Pooled statistics revealed that MSCs group did not improve in less than 3 months of follow-up compared with control group (MD, 7.38%; 95%CI, -2.67 to 17.43; P=0.14; I2=90%). The effect of MSCs in improving LVEF gradually appeared after 4 months of follow-up. However, this beneficial effect seems to diminish over time. LVEF increased by 3.21% (95%CI, 2.91 to 3.50; P<0.00001; I2=0%), 3.56% (95%CI, 1.62 to 5.51; P=0.0003 to I2=87%), 2.48% (95%CI, 1.16 to 3.80; P=0.0002; I2=93%) and 0.81% (95%CI, 0.37 to 1.24; P=0.0003; I2=0%) in 4, 6, 12 and 24 months respectively (Fig. 7a). We performed a sensitivity analysis for the subgroup at 6-month and 12-month follow-up. When omitting the studies one by one, we did not find the opposite result. Interestingly, when we ignore the results from Chen et al., 2004 [19] and Gao et al., 2013 [20], I2 change from 87% to 0% in the 6-month group; delete the result from Chullikana et al., 2015, I2 decreased from 93% to 0% in the 12-month. In the result of 2015, the I2 value changed from 93% to 0% (Fig. 7b). However, in cardiac parameters of LVESV and LVEDV, we have not found that MSCs treatment has a significant improvement effect, which may be related to the existence of heterogeneity (Fig. 8).
2.5 The dose of MSCs therapy
According to the combined data of dose subgroup, patients who injected more than 108 cells did not benefit more than patients with low cell doses. More specifically, for patients who received cell doses between 107 and 108, LVEF was significantly improved by 2.62% (95%CI, 1.54 to 3.70; P<0.00001; I2=0%). However, this result was not observed in the high cell dose group (>108 cells) (Fig. 9).
2.6 The timing of MSCs therapy
Compared with the control group, MSCs transplantation within 2 days after AMI did not significantly improve LVEF. Cell therapy within 2 to 14 days after AMI increased LVEF by 3.18% (95%CI, 2.89 to 3.47; P<0.00001; I2=0%). For cell transplantation >14 days after PCI, LVEF also increased significantly by 3.37% (95%CI, 1.04 to 5.69; P=0.004; I2=89%), but there was a high degree of heterogeneity (Fig. 10a). Further sensitivity analysis, we found that when Chen et al., 2004 [19] and Gao et al., 2013 [20] were ignored, the I2 value dropped from 89% to 23%. The improvement of LVEF in the transplantation group greater than 14 days seems to be lower than that in the transplantation group within 2 to 14 days (Fig. 10b).
2.7 The safety of MSCs therapy
7 studies reported all-cause mortality (OR 1.86; 95%CI,0.39 to 8.90; I2=0; P=0.44 (Fig. 11). The data shows that compared with the control group, MSC treatment was safe for patients with AMI.