家兎総頸動脈における内膜切除術後の内膜再生機序についての実験的検討 : 標準食飼育群と高コレステロール食飼育群におけるspindle typeとovoid type細胞について

Endothelial regeneration of the rabbit carotid artery was investigated after endarterectomy, which involved the removal of a 4 mm length including the endothelium, internal elastic laminae and part of the muscle layer of the media. Regeneration was studied at intervals from 1 hour to 8 weeks after surgery. There were two groups, Group A consisting of Japan White rabbits fed a standard diet and Group B consisting of rabbits fed a 1% cholesterol diet for a month prior to surgery and continued until the annimals were sacrificed. The healing process of the endarterectomized arterial wall was observed using light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The origin of regenerated cells was examined with immunohistochemical double-labeled staining. Scanning electron microscopy (SEM) showed two kinds of regenerated cells which were observed on the luminal surface of the endarterectomized wall, namely, spindle type and ovoid type cells in both Group A and Group B. Complete endothelial regrowth was confirmed 2 weeks after surgery in both groups. After the endothelial regrowth was completed, the ovoid type cells were localized in the low shear stress area. Transmission electron microscopy (TEM) showed both the spindle type and ovoid type cells consisted of pinocytotic vesicles and demonstrated tight-junction adherence, which confirmed their endothelial origin. Immunohistochemical findings showed both the spindle type and ovoid type cells stained positively for anti-Factor VIII antibody in Group A and stained positively for anti-CD31 antibody in Group B, which confirmed their endothelial origin. In Group B the speed of the endothelial regrowth was not remarkably delayed from that in Group A, but SEM revealed enlarged spindle type cells and irregular-sized ovoid type cells. TEM showed vacuoles existed in both spindle type and ovoid type cells. In addition, foam cells which were stained for antimacrophage cell antibody RAM11 migrated subendothelially, after which intimal thickening was observed. It could be suggested that the reason for the low rate of clinically postoperative restenosis after carotid endarterectomy is that preoperative control leads to the reduction of risk factors of atherosclerosis, and consequently clinical endothelial regeneration of the human carotid artery after endarterectomy is likely to resemble that of the rabbit carotid artery in Group A.