Repair in arterial tissue

Summary

Mechanical lesion of the descending thoracic aorta of male albino rabbits was performed with an embolectomy catheter and observed as the basic lesion in a correlative study by scanning electron microscopy (SEM) and light microscopy of injury and repair of arterial wall. Fixation and silver-staining were carried out with the aortas in situ. Specimens collected 3, 6, 14, 30, 60, and 180 days after injury were studied en face by SEM and light microscopy, and sectioned tissue was submitted to histochemical investigations, reaffirming previous observations on embolectomy catheter lesion. Shamoperated animals were used as controls.

The observations by SEM and by surface light microscopy were the same: initial, severe trauma of the intimal surface followed by re-endothelialization from preserved endothelium on the aortic surface and around the intercostal arteries. In silver-stained specimens three main types of cellular patterns were recognized: hexagonal cells, foam-like patterns of cells, and polarized cells. The hexagonal cells were “true” endothelial cells, whereas the origin of the foam-like patterns of cells was less clear. From a comparison of the observations made in the present study and those recorded in morphological studies by other authors it is concluded that 1) re-endothelialization of rabbit thoracic aorta following extensive endothelial injury is slow, 2) re-endothelialization with “true” endothelium takes place from pre-existing endothelial areas, 3) the exposed arterial surface seems to be covered with sheets of cells from two sources, viz. pre-existing endothelium and cells originating from the blood and/or from the underlying tissue.