Abstract 18495: Loss of Syndecan-1 Results in De-differentiation of Vascular Smooth Muscle Cells
Introduction: Vascular smooth muscle cells (vSMCs) display a wide phenotypic continuum, altered during the vascular remodeling process in disease or following injury. The phenotypic state of vSMCs, modulated by the cellular microenvironment, can range from a highly proliferative, extracellular matrix-synthesizing phenotype to a highly differentiated, contractile phenotype. Syndecans, heparan sulfate proteoglycans serving as cell surface co-receptors, have emerged as powerful and complex regulators of cell function. However, the ability of syndecan-1 to regulate vSMC differentiation is not yet known.
Hypothesis: We hypothesized that syndecan-1 is a regulator of vSMC phenotype and can consequently regulate the pathophysiology of disease or vessel wall restenosis.
Methods and Findings: To test our hypothesis, we performed gene and protein expression studies for wild-type (WT) and syndecan-1 knockout (S1-KO) mice-derived primary vSMCs. Real time RT-PCR (n=4) indicated higher levels of smooth muscle α-actin (α-SMA), calponin, myosin heavy chain (MYH) II, and desmin, and, lower levels of the embryonic form of smooth muscle MYH in WT relative to S1-KO cells, both in low serum vSMC growth medium and in differentiation medium with heparin and transforming growth factor-β1. Higher α-SMA and calponin levels were corroborated using Western blots and immunocytochemical studies. Mechanistic studies involving the serine/threonine kinase Akt (involved in vSMC survival and differentiation) and the mTOR downstream target p-S6 ribosomal protein (p-S6RP) indicated that p-Akt tripled and p-S6RP halved in WT cells (n=3). Integrated morphometric analysis indicated that S1-KO cells were 3 times larger area-wise, more circular, and less elongated, compared to WT. Further, S1-KO cells were about 1.5 times as proliferative as WT (n≥3). Immunocytochemical assessments to evaluate the effect of syndecan-1 knockout on syndecan-1 binding proteins indicated that syntenin, cortactin, and vinculin were present in significantly higher amounts in WT compared to S1-KO cells.
Conclusion: Taken together, our results support a positive role for syndecan-1 in promoting vSMC differentiation, reducing the chances of intimal hyperplasia after vascular injury.
- © 2012 by American Heart Association, Inc.