“…This indicates that the earlier developmental stages are crucial in establishing a balanced interaction between the differ ent cell types involved in vasculogenesis [47,126,184,185], In very early stages of development, locally re cruited [27,136,184] mesenchymal cells, lacking SM-specific structural attributes [27,75,99,132,153], move into the region surrounding small endothelial tubes. Later on these cells assume some structural characteristics of SMCs and incorporate in the wall as cellular layers [2,116,136,154]. SMC proliferation and differentiation occurring in the formation of the arterial wall appear to be controlled by locally activated autocrine/paracrine mech anisms present in cells of the growing arterial wall which might contribute to the maturation process [184], Structural maturation proceeds in such a way that SMC lose their ability to proliferate [33,77], their fibroblast-like appearance, and become filled with myofila ments [60,153,198], The physiological hypertrophy of SMC [23,24] which takes place at this time is accompa nied by a progressive accumulation of cells with a tetraploid nuclear content [160].…”