**1. Introduction**

Vascular smooth muscle cells (VSMCs) are the major cell type in the vascular wall and their main role is contraction. VSMCs in the normal aorta are classified as having a contractile phenotype because they contract without proliferation. Conversely, VSMCs in vascular diseases, such as restenosis after percutaneous coronary intervention and the formation of atherosclerotic plaques, are described as having a synthetic phenotype because they can proliferate and migrate, but lose their ability to contract. The phenotypic modulation of VSMCs depends on the surrounding environment [1].

In order to conduct basic studies on the physiological function of VSMCs and to develop novel medical treatments, cultured VSMCs are used. When VSMCs are cultured on a plastic plate in the presence of 10% fetal bovine serum (FBS), which is the normal two-dimensional monolayer culture system, the cells can migrate and proliferate, but lose their contractile ability [2]. Cultured VSMCs are classified as having a synthetic phenotype and are used as a model of atherosclerotic lesion cells. As phenotypic modulation of VSMCs is responsible for restenosis and the progression of atherosclerosis, they could be the main target of medicinal treatment, and VSMCs cultured on plates are useful to evaluate the effects of medicines. However, there is no acceptable cell model that reflects the nature of VSMCs in the normal aorta of a living body. For this reason, information generated from synthetic VSMCs cannot be compared with that from contractile VSMCs in the normal aorta. In this chapter, we describe a new culture system for VSMCs that maintain their contractile phenotype.
