SMOOTH-MUSCLE LINEAGE DIVERSITY IN THE CHICK-EMBRYO - 2 TYPES OF AORTIC SMOOTH-MUSCLE CELL DIFFER IN GROWTH AND RECEPTOR-MEDIATED TRANSCRIPTIONAL RESPONSES TO TRANSFORMING GROWTH-FACTOR-BETA

Lineage analysis studies in the avian embryo have identified two types of smooth muscle cells (SMCs) in the tunica media of large elastic ar teries; one that originates within the cardiac neural crest and is ect oderm in origin (Ect) and another that arises from local mesenchyme of mesodermal origin (Mes). To determine if differences in primary embry onic lineage can give rise to SMCs with stable differences in growth a nd differentiation properties, we isolated Ect and Mes SMCs from the D ay 14 chick embryo aorta. me report that despite different primary emb ryonic origins, Ect and Mes SMCs express nearly identical levels of se ven SMC differentiation markers in vitro, consistent with their common smooth muscle developmental fates in vivo. By contrast, Ect SMCs disp layed a greater capacity for growth in serum-free medium than Mes SMCs , but only under conditions permitting short-range cell-cell interacti ons. Most of the peptide growth factors tested that might account for serum-independent growth (PDGF-AA, PDGF-BB, basic FGF, EGF, or activin ) stimulated DNA synthesis to similar extents in Ect and Mes SMCs. How ever, we found dramatic, lineage-dependent differences in SMC response s to transforming growth factor-beta (TGF-beta). Exposure to TGF-beta 1 (0.4 to 400 pmole/liter) consistently increased DNA synthesis in Ect SMCs, whereas in paired cultures of Mes SMCs, TGF-beta 1 was growth i nhibitory. In SMC cultures transfected with p3TP-lux, a luciferase rep orter controlled by the TGF-beta 1-response elements of the human PAI- I promoter, TGF-beta 1 (120 pM) produced 12+/-2-fold increases in luci ferase activity in Ect SMCs and only 3+/-1.5-fold increases in Mes SMC s. Analysis of TGF-beta receptor phenotypes by Northern blot, radiolig raad binding, and crosslinking assays showed that Ect and Mes SMCs exp ressed similar levels of types I, II, and III TGF-beta receptors. Howe ver, using a polyclonal antibody specific for the chick type Il TGF-be ta receptor subunit, we demonstrate that. Mes SMCs produce a fully gly cosylated form of this protein while Ect SMCs elaborate only an unglyc osylated type II TGF-beta receptor. These results show that Ect and Me s SMCs exhibit lineage-dependent differences in growth and receptor-me diated transcriptional responses to at least one important class of SM C morphogens and growth modifiers, e.g., the TGF-beta s. Our findings suggest that different SMC populations within a common vessel wall may respond in lineage-dependent ways to signals that direct formation of the tunica media in the embryo and to factors involved in the progres sion of vascular disease later in life. (C) 1996 Academic Press, Inc.