Expression of smooth muscle alpha-actin in mesenchymal cells during formation of avian endocardial cushion tissue: A role for transforming growth factor β3

Abstract

During early cardiac morphogenesis, outflow tract (OT) and atrio‐ventricular (AV) endothelial cells differentiate into mesenchymal cells, which have characteristics of smooth muscle‐like myofibroblasts, and which form endocardial cushion tissue, the primordia of valves, and septa in the adult heart. During this embryonic event, transforming growth factor β3 (TGFβ3) is an essential element in the progression of endothelial‐transformation into mesenchyme. TGFβs are known to be a potent inducer for mesodermal differentiation and a promoter for differentiation of endothelial cells into smooth muscle‐like cells. Using a monoclonal antibody against smooth muscle‐specific alpha‐actin (SMA), we examined the immunohistochemical staining of this form of actin in avian endocardial cushion tissue formation. To determine whether TGFβ3 initiates the expression of SMA, the pre‐migratory AV endothelial monolayer was cultured with or without chicken recombinant TGFβ3 and the expression of SMA was examined immunochemically. Migrating mesenchymal cells expressed SMA beneath the cell surface membrane. These cells showed a reduction of endothelial specific marker antigen, QH1. Stationary endothelial cells did not express SMA. The deposition of SMA in the mesenchymal tissue persisted until the end of the fetal period. Pre‐migratory endothelial cells cultured in complete medium (CM199) that contained TGFβ3 expressed SMA, whereas cells cultured in CM199 alone did not. At the onset of the endothelial‐mesenchymal transformation, migrating mesenchymal cells express SMA and the expression of this form of actin is upregulated by TGFβ3. The induction of the expression of SMA by TGFβ3 is one of the initial events in the cytoskeletal reorganization in endothelial cells which separate from one another during the initial phenotypic change associated with the endothelial‐mesenchymal transformation. Dev. Dyn. 209:296–309, 1997. © 1997 Wiley‐Liss, Inc.

Molecular basis of endothelial cell morphogenesis in three‐dimensional extracellular matrices

“…Croix et al (2000), many of the upregulated ECM genes from tumor-derived ECs were characteristically produced by mesenchymal cells such as collagen type I and collagen type III genes. This suggests the possibility that angiogenic ECs in colorectal carcinomas are undergoing an epithelial-mesenchymal transition, which is observed when epithelial or ECs invade interstitial matrices (Nakajima et al, 1997;Boyer et al, 2000;Savagner, 2001). In contrast, Bell et al (2001) showed that marked inductions of basement membrane matrix genes characteristic of EC differentiation were observed during EC morphogenesis in collagen matrices.…”

Smooth Muscle Progenitor Cells in Human Blood

“…2 Several growth factors have been implicated in embryonic smooth muscle cell differentiation, including transforming growth factors ␤ 1 , ␤ 3 , and platelet-derived growth factor BB (PDGF-BB). [2][3][4] Recently, Yamashita et al 5 reported embryonic vascular progenitors capable of differentiating into both endothelial and smooth muscle-like cells in response to vascular endothelial growth factor (VEGF) and PDGF-BB selection, respectively. Presently, there is no evidence for such growth factor-driven differentiation events in adult human subjects.…”

Possible involvement of protein kinase C activation in differentiation of human umbilical vein endothelium‐derived cell into smooth muscle‐like cell

“…Neointimal SMCs have for some time been believed to originate locally from the SMCs of the medial layer (Ross, 1993;Ross, 1999). However, several recent studies have suggested that SMC-like cells can arise from ECs (Arciniegas et al, 1992;DeRuitar et al, 1997;Nakajima et al, 1997;Frid et al, 2002). In addition, in our previous study we found that not only HUVE-DCs, but also human adult pulmonary artery ECs (HPAECs) have the potential to differentiate into smooth muscle-like cells (Ishisaki et al, 2003).…”

“…Fibroblast growth factors (FGFs) play key roles in the induction of both angioblasts (Poole et al, 2001) and haemangioblasts (Poole et al, 2001;Cox and Poole, 2000) from the mesoderm, and most endothelial precursors divide and differentiate in response to vascular endothelial growth factor (VEGF) (Raffi, 2000;Isner and Asahara, 1999). Although the above is true in general, several studies have suggested that SMC-like cells can arise from atrio-ventricular and dorsal aorta ECs (Arciniegas et al, 1992;DeRuitar et al, 1997;Nakajima et al, 1997;Frid et al, 2002). For instance, transforming growth factor b1 (TGF-b1) was found to induce an expression of smooth muscle a-actin (SM-aActin) both in bovine aortic ECs (Arciniegas et al, 1992) and in mesenchymal cells (Nakajima et al, 1997).…”

“…Although the above is true in general, several studies have suggested that SMC-like cells can arise from atrio-ventricular and dorsal aorta ECs (Arciniegas et al, 1992;DeRuitar et al, 1997;Nakajima et al, 1997;Frid et al, 2002). For instance, transforming growth factor b1 (TGF-b1) was found to induce an expression of smooth muscle a-actin (SM-aActin) both in bovine aortic ECs (Arciniegas et al, 1992) and in mesenchymal cells (Nakajima et al, 1997). Furthermore, one recent study suggested that both ECs and SMCs develop from the same precursor: Flk1-expressing cells derived from embryonic stem cells (Yamashita et al, 2000).…”