Vascular Smooth Muscle Cells as a Valvular Interstitial Cell Surrogate in Heart Valve Tissue Engineering

BACKGROUND: Vascular smooth muscle cells (VSMCs) are a potential autologous cell source for aortic valve tissue engineering, but have a phenotype that differs from that of valvular interstitial cells in vivo. We hypothesized that combining basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), or platelet-derived growth factor (PDGF) with transforming growth factor beta-1 (TGF-beta1) would achieve a valvular interstitial cell-like phenotype of VSMCs. METHODS: VSMC phenotype was assessed by immunofluorescence, proliferation was measured by the tetrazolium reduction (MTT) assay, and extracellular matrix gene expression was determined by real-time polymerase chain reaction. RESULTS: Combinations of growth factors that included PDGF showed the greatest increases in proliferation. Immunofluorescence for alpha-smooth muscle actin demonstrated an inverse correlation between proliferation and a myofibroblast-like phenotype, while combinations of TGF-beta1+ EGF+bFGF (TEF) and TGF-beta1+EGF+PDGF (TEP) induced the greatest change of alpha-smooth muscle actin expression compared to untreated controls. Finally, TEP treatment showed an increase in versican, fibronectin, and type I collagen mRNA expression, while decreasing matrix metalloproteinase 1 expression. CONCLUSIONS: Combination of TGF-beta1 with EGF and PDGF induces VSMC proliferation and expression of extracellular matrix constituents found in the aortic valve. In vitro preconditioning of VSMCs provides a potentially viable surrogate cell source for developing a valve graft.