Fibroblasts are mesenchymal cells which came from the embryonic mesoderm. They are useful tools for several cellular and molecular studies; as they are one of easiest types of cells to grow in culture. Their durability also makes them amenable to a variety of manipulations ranging from studies employing gene transfection to microinjection. Fibroblasts in the vascular adventitia, the outermost connective tissue covering of a vessel, are related to vascular injuries through transient changes in their phenotypic and proliferative properties; but also due to accumulation of extracellular matrix proteins in the adventitia. Such changes play an important role in the remodeling of vessel walls under pathological conditions; and thus suggest great potential for site-specific vascular wall gene therapy to regulate vascular tone through vascular adventitial fibroblasts