Integrin β1 Increases Stem Cell Survival and Cardiac Function after Myocardial Infarction

Abstract

Bone mesenchymal stem cells (BMSCs) transplantation is a promising therapeutic approach for myocardial infarction (MI), but its application is limited by poor viability of BMSCs. In this study, we aimed to improve the survival of BMSCs by lentivirus vector mediated overexpression of integrin β1. In vitro study showed that integrin β1 overexpression could facilitate the proliferation of BMSCs under oxygen glucose deprivation condition and regulated the expression of Caspase-3, Bax, Bcl-2, FAK, and ILK in BMSCs. Next, MI was induced in rat model and Igtb1BMSCs, NullBMSCs, or NatBMSCs were transplanted by intramyocardial injection. One week later, the survival of BMSCs was higher in Itgb1 BMSCs group than in other groups. Four weeks after transplantation, heart function was significantly improved in Igtb1BMSCs group compared to other groups. The expression levels of Caspase-3 and Bax were decreased while the expression levels of Bcl-2, FAK, ILK, and VEGF were increased in the cardiomyocytes of Igtb1BMSCs group compared to other groups. In conclusion, integrin β1 overexpression could increase the survival of BMSCs and improve the efficacy of transplanted BMSCs for MI treatment. The beneficial effects may be mediated by inhibiting the apoptosis of both transplanted BMSCs and cardiomyocytes through adhesion-mediated cell survival signaling.

Keywords: adhesion; apoptosis; bone mesenchymal stem cell; integrin β1; myocardial infarction.

Figure 1

Expression of integrin β1 in BMSCs. (A) BMSCs were observed under fluorescent microscope (MOI = 1:20); (B,C). RT-PCR analysis of integrin β1 mRNA expression. (D,E). Western blot analysis of integrin β1 expression. Fold change of integrin β1 level was calculated after normalization to ^NatBMSCs (set as 1). #p < 0.01 vs. ^NatBMSCs and ^NullBMSCs.

Figure 2

The survival of BMSCs under oxygen glucose deprivation. Cell survival was analyzed by CCK8 assay. #p < 0.05 vs. ^NatBMSCs and ^NullBMSCs.

Figure 3

The apoptosis of BMSCs under oxygen glucose deprivation. (A) Representative TUNEL staining of BMSCs. Apoptotic cells had red staining in the nuclei, while all cells were stained blue by DAPI. (B) Quantitative analysis of TUNEL staining. #p < 0.01 vs. ^NatBMSCs and ^NullBMSCs.

Figure 4

The expression of apoptosis and adhesion related proteins in BMSCs under oxygen glucose deprivation. (A) Western blot analysis of apoptosis related proteins. β-actin was loading control. (B) Densitometry analysis of fold change of protein levels. Protein levels in ^NatBMSCs were set as 1. (C) Western blot analysis of adhesion related proteins. β-actin was loading control. (D) Densitometry analysis of fold change of protein levels. Protein levels in ^NatBMSCs were set as 1. #p < 0.01 vs. ^NatBMSCs.

Figure 5

Integrin β1 overexpression improved cardiac function in rat model of MI. (A) ECG showed elevated ST segment in rat model of MI. (B–F) Echocardiographic assessment of cardiac function in four groups of rats. ^Itgb1BMSCs group, ^NullBMSCs group, ^NatBMSCs group, and Saline group were injected into the periphery region of infarcted myocardium with ^Itgb1BMSCs, ^NullBMSCs, ^NatBMSCs, and saline, respectively. #p < 0.01 vs. Saline group; ^*p < 0.05 vs. Saline group; ‡p < 0.01 vs. ^NatBMSCs group.

Figure 6

Survival of transplanted BMSCs. (A) Representative images showing significant increase of transplanted BMSCs in ^Itgb1BMSCs group. Survived BMSCs were marked by the arrows and they were stained blue by DAPI. (B) Quantitative analysis of the number of survived BMSCs in each field. ‡p < 0.01 vs. ^NullBMSCs group.

Figure 7

Immunohistochemical analysis of FAK and Caspase-3 in the myocardium of different groups of rats. (A) Representative immunohistochemical images. (B,C) Quantitative analysis of the expression of FAK and Caspase-3. #p < 0.01 vs. Saline group; ‡p < 0.01 vs. ^NatBMSCs group.

Figure 8

Expression levels of apoptosis and adhesion related proteins in the myocardium of different groups of rats. ^Itgb1BMSCs group, ^NullBMSCs group, ^NatBMSCs group, and Saline group were injected into the periphery region of infarcted myocardium with ^Itgb1BMSCs, ^NullBMSCs, ^NatBMSCs, and saline, respectively. (A) Western blot analysis of apoptosis and adhesion related proteins. β-actin was loading control. (B) Densitometry analysis of fold change of protein levels. #p < 0.01 vs. Saline group; ^*p < 0.05 vs. Saline group; ‡p < 0.01 vs. ^NatBMSCs group.