Figure 4

Hypothetical origin of neointimal SMCs. (a) SMCs of the media (after switching into migratory phenotype) transmigrate into newly forming neointima. (b) SMCs present in the media undergo apoptosis. Stem/progenitor cells and resident fibroblasts present in adventitia acquire migratory phenotype and transmigrate into intima where they proliferate and differentiate into SMCs. (c) SMCs present in the media undergo apoptosis. Bone marrow progenitor cells (and possibly also circulation-derived CD34⁺ hematopoietic progenitor cells) acquire migratory phenotype, migrate into the intima, proliferate, and differentiate into SMCs.