The effects of endothelial injury on smooth muscle cell proliferation

The endothelial injury induced by the placement of a synthetic graft has been implicated as a stimulus for the development of MIH. In this study we compared the degree of EC coverage and the early SMC-PR in the arterial segments proximal and distal to 2 mm diameter PTFE grafts that had been placed in rabbit carotid arteries (n = 49). In vivo labeling with 3H-thymidine and Evans blue was carried out at intervals of 2 to 33 days after grafting. The SMC-PR was measured as the degree of 3H-labeled DNA divided by the total DNA for each segment, and the EC coverage was determined by planimetry of the area of Evans blue exclusion. There was an early rise in the SMC-PR in both arterial segments, but it was more marked in the distal segment (p less than 0.001). There was no correlation between the SMC-PR and the degree of EC coverage in either the proximal (r = 0.25) or the distal segments (r = 0.10). The data suggest that there is a greater SMC-PR at the distal end of an implanted PTFE graft. The degree of endothelial loss and its regrowth does not appear to be an important factor.