Thymosin beta 4 impeded murine stem cell proliferation with an intact cardiovascular differentiation

Thymosin beta 4 (T beta 4) is a key factor in cardiac development, growth, disease, epicardial integrity, blood vessel formation and has cardio-protective properties. However, its role in murine embryonic stem cells (mESCs) proliferation and cardiovascular differentiation remains unclear. Thus we aimed to elucidate the influence of T beta 4 on mESCs. Target genes during mESCs proliferation and differentiation were detected by real-time PCR or Western blotting, and patch clamp was applied to characterize the mESCs-derived cardiomyocytes. It was found that T beta 4 decreased mESCs proliferation in a partial dose-dependent manner and the expression of cell cycle regulatory genes c-myc, c-fos and c-jun. However, mESCs self-renewal markers Oct4 and Nanog were elevated, indicating the maintenance of self-renewal ability in these mESCs. Phosphorylation of STAT3 and Akt was inhibited by T beta 4 while the expression of RAS and phosphorylation of ERK were enhanced. No significant difference was found in BMP2/BMP4 or their downstream protein smad. Wnt3 and Wnt11 were remarkably decreased by T beta 4 with upregulation of Tcf3 and constant beta-catenin. Under mESCs differentiation, T beta 4 treatment did not change the expression of cardiovascular cell markers alpha-MHC, PECAM, and alpha-SMA. Neither the electrophysiological properties of mESCs-derived cardiomyocytes nor the hormonal regulation by Iso/Cch was affected by T beta 4. In conclusion, T beta 4 suppressed mESCs proliferation by affecting the activity of STAT3, Akt, ERK and Wnt pathways. However, T beta 4 did not influence the in vitro cardiovascular differentiation