HETEROGENEITY IN MIGRATION OF SMOOTH-MUSCLE CELLS FROM NORMAL AND INJURED RAT THORACIC AORTA IN PRIMARY CULTURE

Objective: Aside from proliferation, migration of smooth muscle cells is an essential component of the arterial sclerotic reaction. The aim of this study was to define a model to study migration. Methods: Prima ry cultures of smooth muscle cells were derived from normal or injured rat thoracic aorta. An image analysis system was used to track cells migrating out of the explants and measure the displacement of their ce ntre of gravity. Results: Migration speeds for smooth muscle cells ran domly sampled from the normal whole media were very heterogeneous. The media were therefore separated into three vertical segments. Cells fr om the middle third migrated faster than those from the upper and lowe r thirds, regardless of whether they originated from the anterior and posterior parts of the segment (P = 0.001). Heparin (10 mu g.ml(-1)) o nly inhibited smooth muscle cell migration from the middle segment (P < 0.001). Migration of smooth muscle cells from explants of aorta 3 an d 14 d after injury was also studied using a balloon catheter. Three d ays after injury, cell velocity varied widely among the segments of th e same media. In contrast, 14 d after injury cells from neointimal exp lants migrated homogeneously and at a slower rate than those obtained from normal media. Conclusions: These experiments show migratory varia tions among smooth muscle cells depending upon their position in the n ormal aorta and their state of activation after arterial injury. This variability must be taken into account when planning experiments to st udy smooth muscle cell migration.