Endothelial cell proliferation in swine experimental aneurysm after coil embolization.

After coil embolization, recanalization in cerebral aneurysms adversely influences long-term prognosis. Proliferation of endothelial cells on the coil surface may reduce the incidence of recanalization and further improve outcomes after coil embolization. We aimed to map the expression of proliferating tissue over the aneurysmal orifice and define the temporal profile of tissue growth in a swine experimental aneurysm model. We compared the outcomes after spontaneous thrombosis with those of coil embolization using histological and morphological techniques. In aneurysms that we not coiled, spontaneous thrombosis was observed, and weak, easily detachable proliferating tissue was evident in the aneurysmal neck. In contrast, in the coil embolization group, histological analysis showed endothelial-like cells lining the aneurysmal opening. Moreover, immunohistochemical and morphological analysis suggested that these cells were immature endothelial cells. Our results indicated the existence of endothelial cell proliferation 1 week after coil embolization and showed immature endothelial cells in septal tissue between the systemic circulation and the aneurysm. These findings suggest that endothelial cells are lead to and proliferate in the former aneurysmal orifice. This is the first examination to evaluate the temporal change of proliferating tissue in a swine experimental aneurysm model

Intra- and postoperative angiograms.

<p>(<b>A</b>) Intraoperative views of the sidewall-type aneurysm a) before and b) after coil embolization. (<b>B</b>) a and c) intraoperative angiograms; d) angiogram obtained immediately after coil embolization; and b and e) angiogram obtained 1 week after surgery.</p

Evaluation of the aneurysmal orifice.

<p>(<b>A</b>) Photomicrographs of aneurysmal orifices 1, 2 and 4 weeks after the operation. (<b>B</b>) The proportion of proliferating tissue covering the aneurysmal orifice in the embolization and control groups. Data are mean ± SEM of three swine in each group. *<i>P</i><0.05, **<i>P</i><0.001, compared with the control group.</p

Immunohistochemical analysis of proliferating cells.

<p>(<b>A</b>) Photomicrographs of vWF-positive cells 1, 2 and 4 weeks after surgery in the embolization and control groups. Scale bars = 50, 20 µm (enclosure). (<b>B</b>) Number of vWF-positive cells. (<b>C</b>) Photomicrographs of PCNA-positive cells 1, 2 and 4 weeks after surgery in the embolization and control groups. Scale bars = 50, 20 µm (enclosure). (<b>D</b>) Number of PCNA-positive cells. (<b>E</b>) Photomicrographs of PECAM-1-positive cells 1, 2 and 4 weeks after surgery in the embolization and control groups. Scale bars = 50, 20 µm (enclosure). (<b>F</b>) Number of PECAM-1-positive cells. Bars = 50, 20 µm (enclosure). (<b>G</b>) Photomicrographs of CD34-positive cells 1, 2 and 4 weeks after surgery in the embolization and control groups. Bars = 50, 20 µm (enclosure). (<b>H</b>) Number of CD34-positive cells. Data are mean ± SEM of three swine in each group. *<i>P</i><0.05, **<i>P</i><0.001, compared with the control group.</p