Genetic modification of smooth muscle cells to control phenotype and function in vascular tissue engineering

Rat smooth muscle cells (SMCs) stably transfected with the gene for the phenotype regulating protein cyclic guanosine monophosphate-dependent protein kinase (PKG) were used as a cell source in the preparation of three-dimensional (3D) collagen type I vascular constructs. PKG-transfected cells expressed severalfold higher levels of the contractile protein smooth muscle alpha-actin (SMA), relative to untransfected SMCs, both in monolayer culture and in 3D gels. The proliferation rate of PKG-transfected cells was lower than that of untransfected cells in both culture geometries. Three-dimensional collagen constructs made with PKG-transfected cells compacted to a similar degree as those made with untransfected cells, and this compaction could be augmented by biochemical stimulation with platelet-derived growth factor BB (PDGF) or transforming growth factor beta(1) (TGF). Application of cyclic mechanical strain to tubular collagen gels seeded with PKG-transfected cells resulted in a higher degree of gel compaction and circumferential matrix alignment, relative to statically grown controls, but cell proliferation and SMA expression were not affected. These results show that genetic modification of SMCs can be used as a tool to control cell function in vascular tissue engineering, and that the function of such cells can be further modulated by application of biochemical and mechanical stimulation.