We propose that early changes in the extracellular matrix (ECM) that lead to arterial intimal thickening are due to modifications in the synthesis and interaction of three ECM components: versican (CSPG), hyaluronan (HA) and an HA-binding protein, RHAMM (receptor for HA-mediated motility). We hypothesize that the synthesis of these components by arterial smooth muscle cells (ASMC) is regulated in part by growth factors and that the modifications induced in versican by growth factors influence the adhesion or migration of ASMC. We will test these hypotheses using both in vitro and in vivo approaches, which will focus on human systems. The proposal contains five aims and is designed to examine the involvement of these molecules in vascular biology and pathology.
Aim I will characterize the structural modifications induced in the core glycoprotein and GAG chains of versican by the mitogen, platelet-derived growth factor (pDGF), and the growth inhibitor, transforming growth factor-beta1 (TGF-beta1). Both of these growth factors stimulate versican expression, and their effects on versican will be compared to those induced by interleukin-1(IL-1), which down-regulates versican expression. In this aim, we will focus on the identification of putative splice variants of versican and post- translational changes in the structure of the GAG chain attached to versican.
Aim II will examine the mechanisms by which these growth factors and cytokines regulate versican expression. Thus, experiments have been designed to ask whether regulation of versican expression involves transcriptional or post-transcriptional events, and whether growth factors independently regulate versican protein and GAG synthesis. In the third aim, we will examine whether the synthesis of HA and RHAMM, which interact with versican to form macromolecular complexes, is regulated in parallel with versican. We will also ascertain whether the formation of such macromolecular complexes is critical to the assembly and expansion of ASMC pericellular matrix, or influences ASMC migration.
The fourth aim will test whether versican and HA regulate vascular cell adhesion, and whether specific domains within versican are responsible for mediating interactions with cell surface or matrix ligands. The last aim will determine whether versican, HA and RHAMM are expressed and deposited in specific temporal or spatial patterns that characterize specific phases in the development of vascular lesions. In this work, we will focus on the examination of lesions that form following arterial injury and during vascular restenosis. We will also test whether altering the pattern of versican expression in vascular lesions influences lesion development. Identification of the mechanism(s) that regulate the expression of these macromolecules and studies designed to examine the relationships between their structure and their function within vascular tissue offer the potential for targeted therapeutic intervention and interruption of vascular lesion development.
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