Transforming Growth Factor-β-Induced Differentiation of Smooth Muscle From a Neural Crest Stem Cell Line

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Abstract
During vascular development, nascent endothelial networks are invested with a layer of supporting cells called pericytes in capillaries or smooth muscle in larger vessels. The cellular lineage of smooth muscle precursors and factors responsible for regulating their differentiation remain uncertain. In vivo, cells derived from the multipotent neural crest can give rise to vascular smooth muscle in parts of the head and also the cardiac outflow tract. Although transforming growth factor-β (TGF-β) has previously been shown to induce some smooth muscle markers from primary cultures of neural crest stem cells, the extent of the differentiation induced was not clear. In this study, we demonstrate that TGF-β can induce many of the markers and characteristics of vascular smooth muscle from a neural crest stem cell line, Monc-1. Within 3 days of in vitro treatment, TGF-β induces multiple smooth muscle-specific markers, while downregulating epithelial markers present on the parent cells. Treatment with TGF-β also induces a contractile phenotype that responds to the muscarinic agonist carbachol and is not immediately reversed on TGF-β withdrawal. Examination of the signaling pathways involved revealed that TGF-β activation of Smad2 and Smad3 appear to be essential for the observed differentiation. Taken together, this system provides a novel model of smooth muscle differentiation that reliably recapitulates the process observed in vivo and allows for dissection of the pathways and processes involved in this process.