PHENOTYPIC MODIFICATION OF ARTERIAL SMOOTH-MUSCLE CELLS IN RESPONSE TO MEDIAL DISSECTION

Background In the treatment of peripheral arteries, percutaneous trans luminal angioplasty is commonly associated with intimal tears and diss ections. Objective To investigate the influence of medial dissection o n the remodelling of the vessel wall after balloon injury. Methods Aor tae were obtained from 14 Fauve de Bourgogne rabbits that had been fed a normal diet. Seven days after the initial pull-back injury, the aor tae were examined using morphometric and immunocytochemical methods. R esults Eight rabbits (57%) had a tear that extended into the media. Mo rphometric measurements showed that the intima was significantly thinn er when there was a medial dissection [(18.3 +/- 6.9) x 10(-3) versus (39.1 +/- 3.5) x 10(-3) mm without dissection, P < 0.001]. In the medi a of injured vessels, medial dissection was associated with a greater accumulation of extracellular matrix proteins (50.5 +/- 9.7 versus 12. 4 +/- 2.2% of the surface area), a marked reduction in alpha-smooth mu scle actin content (36.6 +/- 5.4 versus 47.4 +/- 7.5% of the surface a rea), a higher expression of a smooth muscle activation antigen (21.2 +/- 5.7 versus 8.9 +/- 1.5% of the 2P1A2-immunostained surface area) a nd an increase in the number of medial proliferating cell nuclear anti gen-positive nuclei (8.2 versus 1.2% of labelled nuclei). Conclusion T hese observations indicated that mechanical injury of the arterial wal l induces a phenotypic activation of medial smooth muscle cells. In th e case of acute distension, the response of the smooth muscle cells in the media was mainly responsible for wound healing in the presence of medial dissection; moreover, acute distension induced a significant h igher state of activation and a medial repairing that could prevent mi gration towards the intimal space. (C) Rapid Science Publishers.