Neointimal Smooth Muscle Cells Research Articles

Recovery of prostacyclin production by de-endothelialized rabbit aorta. Critical role of neointimal smooth muscle cells.

Prostacyclin (PGI2) synthetic capacity was assayed at the surface of aortas at various intervals after removal of endothelium with a balloon catheter. Results were correlated with morphologic changes in the vessel wall seen by light microscopy, scanning and transmission electron microscopy. To assay PGI2 synthetic capacity, we applied an incubation chamber to the luminal surface of the aortas; after arachidonic acid stimulation we assayed the PGI2 synthesized with a bioassay and radioimmunoassay. PGI2 synthesis in de-endothelialized aortas was determined immediately after balloon-catheter injury and at intervals of 1 h and 2, 4, 15, 35, and 70 d. PGI2 synthesis was low at 1 h and increased over time with levels at 35 and 70 d reaching that of normal artery. Scanning and transmission electron microscopy of de-endothelialized areas showed persistent absence of endothelium with formation of a neointima composed of smooth muscle cells. De-endothelialized aorta was covered with adherent platelets shortly after injury, however several days later only a few platelets adhered to the denuded surface. Results indicated that (a) endothelium is responsible for nearly all PGI2 production at the luminal surface of the normal aorta, (b) de-endothelialized muscular neointima synthesized increasing quantities of PGI2 with time after injury, and (c) increase of PGI2 production at the luminal surface of de-endothelialized aorta correlates with formation of a neointima and with the acquired thromboresistance of the aorta.

Pathological changes of anastomotic false aneurysms.

Anastomotic parts of polyester vascular prostheses implanted in thoracic aortae of 270 dogs were examined. Anastomotic false aneurysms were seen with 3 cases (1.2%), in which disruption did not occur, however, the grafts which have no aneurysm showed the following features, i.e., suture migration, degenerative changes of the host arterial wall sustaining a suture and dissection between the host arterial wall and a prosthesis. From the results of an analysis of the arrangement pattern of smooth muscle cells in neointima, it was clarified that a suture had been subjected to continuous tensile stress. So that, the host arterial wall sustaining a suture is clinched and pulled toward prosthesis by the suture at every pulsation during implantation. These results indicate that the features mentioned above are phenomena of the developing into anastomotic false aneurysms.

Pattern of arrangement of smooth muscle cells in neointimae of synthetic vascular prostheses

Neointimae of fabric vascular prostheses of three types (crimped and knitted [A], stretchable [B], and expansile [C]) were examined under both light and electron microscopes from 1 to 1,240 days after implantation in the thoracic aorta of 161 dogs. With all types of prostheses, a very uniform arrangement of smooth muscle cells was observed beneath the endothelial cells. In the crimped and knitted prostheses (A), the smooth muscle cells in the neointima showed a regular arrangement perpendicular to the direction of the bloodstream at each inner ridge of the crimp. In the stretchable prostheses (B), which can stretch only longitudinally, the long axes of the smooth muscle cells oriented in rows parallel to the bloodstream. In the expensive prostheses (C), which can expand only circumferentially, the smooth muscle cells were perpendicular to the bloodstream. These observations suggest that the arrangement of the smooth muscle cells in neointima is largely governed by the tension to which they are subjected.

SEM Observation of Smooth Muscle Cells in Neointima of Synthetic Vascular Prosthesis

SEM Observation of Smooth Muscle Cells in Neointima of Synthetic Vascular Prosthesis