OBJECTIVETo investigate the efficacy of transplantation of mesenchymal stem cells (MSC) with gelatin microspheres containing vascular endothelial growth factor in ischemic regions in infracted swine hearts.

METHODSTwelve Chinese mini swines with infarction were randomized to receive autogenetic MSC injection to the peri-infarction area of left ventricular wall (MSC group, n = 6) or MSC transplantation with gelatin hydrogel microspheres incorporating vascular endothelial growth factor (VEGF-MSC group, n = 6). Three weeks later, left ventricular function was assessed by magnetic resonance imaging (MRI). The contrast of the MSC hypointense lesion was determined using the difference in signal intensity between the hypointense and normal myocardium divided by signal intensity of the normal region. Myocardial capillary density, the number of DAPI positive MSC and the apoptotic MSC were also determined.

RESULTSThe diameter of the microspheres averaged (104.0 +/- 22.6) microm. At 24 hours after transplantation, MSC were identified by MRI as large intramyocardial signal voids at injection sites which persisted up to 3 weeks. There was no significant difference in the contrast of the lesions and in the size of the lesions at 24 hours between two groups. At 3 weeks after injection, the size of the lesions and the contrast of the lesion were decreased (P < 0.05) in both groups. The capillary density of the injection site was significantly more in the MSC-VEGF microsphere group than that in MSC group [(15.2 +/- 5.4)/HPF vs. (10.2 +/- 5.0)/HPF, t = 2.43, P < 0.05], and there were more dense DAPI labeled MSC per high power fields in injection sites of MSC-VEGF microsphere group than that in MSC group [(354 +/- 83)/HPF vs. (278 +/- 97)/HPF, t = 3.14, P < 0.05]. Moreover, the apoptosis rate of MSCs of MSCs-VEGF microsphere group was less than that of MSC group [(6.4 +/- 4.1)% vs. (11.9 +/- 4.8)%, t = 2.97, P < 0.05].

CONCLUSIONSMSC transplantation with gelatin hydrogel microspheres incorporating VEGF enhanced the efficacy of MSC in this swine model of myocardial infarction. MRI tracking of MSC is feasible and represents a preferred method for studying the engraftment of MSCs in infracted tissue.