A novel in vitro model system for smooth muscle differentiation from human embryonic stem cell-derived mesenchymal cells

Guo X, Stice SL, Boyd NL, Chen SY. A novel in vitro model system for smooth muscle differentiation from human embryonic stem cell-derived mesenchymal cells. Am J Physiol Cell Physiol 304: C289-C298, 2013. First published December 5, 2012; doi:10.1152/ajpcell.00298.2012.-The objective of this study was to develop a novel in vitro model for smooth muscle cell (SMC) differentiation from human embryonic stem cell-derived mesenchymal cells (hES-MCs). We found that hES-MCs were differentiated to SMCs by transforming growth factor-beta (TGF-beta) in a dose-and time-dependent manner as demonstrated by the expression of SMC-specific genes smooth muscle alpha-actin, calponin, and smooth muscle myosin heavy chain. Under normal growth conditions, however, the differentiation capacity of hES-MCs was very limited. hES-MC-derived SMCs had an elongated and spindle-shaped morphology and contracted in response to the induction of carbachol and KCl. KCl-induced calcium transient was also evident in these cells. Compared with the parental cells, TGF-beta-treated hES-MCs sustained the endothelial tube formation for a longer time due to the sustained SMC phenotype. Mechanistically, TGF-beta-induced differentiation was both Smad-and serum response factor/myocardin dependent. TGF-beta regulated myocardin expression via multiple signaling pathways including Smad2/3, p38 MAPK, and PI3K. Importantly, we found that a low level of myocardin was present in mesoderm prior to SMC lineage determination, and a high level of myocardin was not induced until the differentiation process was initiated. Taken together, our study characterized a novel SMC differentiation model that can be used for studying human SMC differentiation from mesoderm during vascular development.