The role of versican in the biology of smooth muscle cells and in the engineering of elastin rich blood vessel substitutes

Proteoglycans are extracellular matrix (ECM) macromolecules that interact with other ECM components to influence tissue organization and function. For example, the proteoglycan versican influences the expression and organization of elastin. Small interfering RNAs (siRNAs) were designed and tested for the ability to downregulate the expression of versican in a uterine leiomyosarcoma smooth muscle cell line (SK-LMS-1) that normally expresses abundant versican. Downregulation of versican expression resulted in increased levels of elastin expression, as shown by mRNA, protein, and immunohistochemistry. Moreover, downregulation of versican resulted in slower rates of cell proliferation and migration, increased cell adhesion, decreased hyaluronan (HA) accumulation, and changes in expression of genes associated with elastin synthesis and degradation. Addition of purified versican to siRNA-transduced SK-LMS-1 cell cultures restored cell proliferation to the level of control SK-LMS-1 cells and decreased cell adhesion in a dose-dependent manner. Versican siRNA-transduced SK-LMS-1 cells generated tumors in nude mice that had lower volumes and reduced levels of mitosis compared to control SK-LMS-1 tumors. By immunohistochemistry, the versican siRNA-transduced tumors expressed significantly less versican and HA, but more elastin than did control tumors.;The V3 isoform of versican has been shown to induce elastogenesis in vitro and in vivo and, therefore, could be used to improve the limited elastogenesis that is typical of tissue-engineered blood vessels (TEBVs). Accordingly, smooth muscle cells were transduced to overexpress V3 and specific clonal lines were selected for elevated elastin synthesis. Subsequently, these lines were used to create TEBVs, which were evaluated for levels of elastin mRNA and protein, for deposition/organization of elastin and associated ECM components, and for collagen fiber thickness, burst strength, compliance, stress/strain response, and viability. V3-derived TEBVs had thicker collagen fibers, and greater elastin staining, desmosine content, and compliance than did control TEBVs. In conjunction with V3 overexpression, culture of TEBVs in the absence of ascorbate increased the expression of elastin and elastin-associated proteins.;Collectively, the findings of this dissertation indicate that downregulation of versican using siRNA results in significant increases in elastogenesis that are associated with decreased tumor growth. Furthermore, the overexpression of V3 results in increased elastogenesis and improved performance of TEBVs.