TGF-β induces the differentiation of bone marrow stem cells into immature cardiomyocytes

Transforming growth factor-β₁ (TGF-β₁) was found to induce the myogenic differentiation of bone marrow stem cells (BMSC). We investigated the morphological and electrophysiological properties of differentiated cells, and the mechanisms related to TGF-β₁-induced myogenic differentiation. We found that TGF-β increased the expression of the cardiac transcription factors, GATA-4 and NKx-2.5, in BMSC after 1-3 days of cultivation. TGF-β also induced the expressions of cardiac myosin, troponins, and ANP after 3-14 days of cultivation. However, the Ca²⁺ transient was relatively weak, the connexin-43 expression was irregular, and spontaneous beating was not detected within 28 days observation. TGF-β stimulation up-regulated most of the TGF-β BMP signaling pathway genes, including TGFBI, ACVR2B, and phosphorylated Smad-2 and Smad-3, within 24 h. TGF-β induced the differentiation of BMSC into immature cardiomyocytes by activating the TGF-β BMP signaling pathway.