PDGF-DD, a novel mediator of smooth muscle cell phenotypic modulation, is upregulated in endothelial cells exposed to atherosclerosis-prone flow patterns

Departments of 1 Molecular Physiology and Biological Physics, 2 Biomedical Engineering, and 3 Cardiovascular Medicine and 4 Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, Virginia; 5 Ludwig Institute for Cancer Research, Stockholm Branch, Stockholm, Sweden; 6 Department of Hematology/Oncology, ZymoGenetics, Seattle, Washington; and 7 Laboratory of Molecular Pharmacology, Department of Pharmacy, University of Patras, Patras, Greece Submitted 16 February 2008 ; accepted in final form 20 November 2008 Platelet-derived growth factor (PDGF)-BB is a well-known smooth muscle (SM) cell (SMC) phenotypic modulator that signals by binding to PDGF -, β-, and ββ-membrane receptors. PDGF-DD is a recently identified PDGF family member, and its role in SMC phenotypic modulation is unknown. Here we demonstrate that PDGF-DD inhibited expression of multiple SMC genes, including SM -actin and SM myosin heavy chain, and upregulated expression of the potent SMC differentiation repressor gene Kruppel-like factor-4 at the mRNA and protein levels. On the basis of the results of promoter-reporter assays, changes in SMC gene expression were mediated, at least in part, at the level of transcription. Attenuation of the SMC phenotypic modulatory activity of PDGF-DD by pharmacological inhibitors of ERK phosphorylation and by a small interfering RNA to Kruppel-like factor-4 highlight the role of these two pathways in this process. PDGF-DD failed to repress SM -actin and SM myosin heavy chain in mouse SMCs lacking a functional PDGF β-receptor. Importantly, PDGF-DD expression was increased in neointimal lesions in the aortic arch region of apolipoprotein C-deficient (ApoE –/– ) mice. Furthermore, human endothelial cells exposed to an atherosclerosis-prone flow pattern, as in vascular regions susceptible to the development of atherosclerosis, exhibited a significant increase in PDGF-DD expression. These findings demonstrate a novel activity for PDGF-DD in SMC biology and highlight the potential contribution of this molecule to SMC phenotypic modulation in the setting of disturbed blood flow. shear stress; disturbed blood flow; smooth muscle myosin heavy chain; smooth muscle -actin Address for reprint requests and other correspondence: G. K. Owens, Dept. of Molecular Physiology and Biological Physics, Univ. of Virginia, MR5 Rm. 1220, 415 Lane Rd., PO Box 801394, Charlottesville, VA 22908 (e-mail: gko{at}virginia.edu )