Sorting of murine vascular smooth muscle cells during wound healing in thechicken chorioallantoic membrane

The vascular wall is built up of a heterogeneous population of smooth muscl e cells, which exhibit not only morphological distinctions but also importa nt differences in the composition of their structural and contractile prote ins. "Epithelioid" smooth muscle cells correspond to an intimal-like type a nd display features associated with immaturity, whereas "spindle-shaped" ce lls closely resemble the more typical medial smooth muscle population. We h ave investigated the integration of these two cell types into the vascular architecture of an in vivo wound-healing model. Stably transfected with the beta-galactosidase gene, intima- and media-like cells were injected intrav enously into the chicken chorioallantoic membrane, within which superficial foci of granulation tissue had been created by thermal or chemical injury. At 24 to 72 h after injection, cells had homed in on the lesion sites and were observed in juxtaposition to the endothelial lining of the capillaries . They began to deposit laminin, thereby indicating an impending role in th e formation of the vascular wall. Intima- and media-like smooth muscle cell s did not differ in their capacity to associate with capillaries, and, in s o doing, their biochemical lineage characteristics became indistinguishable from one another. However, intima-like cells also penetrated the adventiti al and medial layers of arteries. These findings reveal vascular smooth mus cle cells to possess an extraordinary degree of plasticity, being able to a dapt flexibly to changes in functional demands. (C) 1999 Academic Press.