GATA-4 promotes myocardial transdifferentiation of mesenchymal stromal cells via up-regulating IGFBP-4

Background aims. GATA-4 is a cardiac transcription factor and plays an important role in cell lineage differentiation during development. We investigated whether overexpression of GATA-4 increases adult mesenchymal stromal cell (MSC) transdifferentiation into a cardiac phenotype in vitro. Methods. MSC were harvested from rat bone marrow (BM) and transduced with GATA-4 (MSC^GATA-4) using a murine stem cell virus (pMSCV) retroviral expression system. Gene expression in MSC^GATA-4 was analyzed using quantitative reverse transcriptionpolymerase chain reaction (RT-PCR) and Western blotting. Native cardiomyocytes (CM) were isolated from ventricles of neonatal rats. Myocardial transdifferentiation of MSC was determined by immunostaining and electrophysiologic recording. The transdifferentiation rate was calculated directly from flow cytometery. Results. The expression of cardiac genes, including brain natriuretic peptide (BNP), Islet-1 and α-sarcomeric actinin (α-SA), was up-regulated in MSC^GATA-4 compared with control cells that were transfected with Green Fluorescent Protein (GFP) only (MSC^Null). At the same time, insulin-like growth factor-binding protein (IGFBP)-4 was significantly up-regulated in MSC^GATA-4. A synchronous beating of MSC with native CM was detected and an action potential was recorded. Some GFP ⁺ cells were positive for α-SA staining after MSC were co-cultured with native CM for 7 days. The transdifferentiation rate was significantly higher in MSC^GATA-4. Functional studies indicated that the differentiation potential of MSC^GATA-4 was decreased by knockdown of IGFBP-4. Conclusions. Overexpression of GATA-4 significantly increases MSC differentiation into a myocardial phenotype, which might be associated with the up-regulation of IGFBP-4.