Abstract 5051: GATA-4 Promotes Mesenchymal Stem Cells Transdifferentiation Into Cardiomyocyte via Insulin Growth Factor Binding Protein 4 Upregulation
It has been reported that GATA-4 stimulates differentiation of beating cardiomyocytes from stem cell. However, the underlying mechanism remains unknown. We hypothesize that GATA-4 enhances MSC mediated myogenesis via upregulating insulin growth factor binding protein 4 (IGFBP-4).
Method: MSC were isolated from rat bone marrow and transfected with GATA-4 (MSCGATA-4) using Clontech pMSCV retroviral expression system. MSC transfected with GFP (MSCGFP) was used as control. Cardiomyocytes (CM) were obtained from neonatal rat ventricles. The transdifferentiation of MSC was directly studied by co-culture MSC with CM, and confirmed by immunostaining and quantitative PCR.
Results: GATA-4 not only remarkably upregulated the expression of myogenic genes (Table⇓), but also significantly increased the expression of IGFBP-4 (9.21±0.60 fold in MSCGATA-4) compared to those in MSCGFP. After co-culture with CM for 7 days, some MSC were tested positive for α-actinin (Fig. A⇓). The percentage of α-actinin positive green cells was significantly higher in MSCGATA-4 (34.9%) than that in MSCGFP (8.6%). The expression of cardiac markers, including BNP, Nkx2.5 and Islet-1 was significantly increased in MSCGATA-4 (Fig. B⇓). Transdifferentiated MSC also showed action potential which was similar to the native CM. To determine whether IGFBP-4 enhanced MSC mediated myogenesis, IGFBP-4 neutralizing antibody (20~40μg/ml) was added into culture medium, which attenuated MSCGATA-4 differentiatiation into cardiomyocyte.
Conclusion: GATA-4 promotes MSC differentiation into myocardial phenotypes partially via upregulating IGFBP-4.