Application of a novel intravascular stent prepared by metal powder injection molding in animals
Objective: To assess the feasibility and safety of using a novel intravascular stent in clinical practice through animal experiment. Methods: Thirty intravascular stents prepared by metal powder injection molding were implanted into the aorta of 30 experimental dogs, respectively. After implantation, the intra-aortic conditions were observed by computed tomography angiography, and the neointimal formations on the stent surface at different postoperative times were observed by gross visual inspection and microscopic and electron microscopic evaluation as well as immunohistochemical staining. Results: All intravascular stents were successfully implanted into the aorta of the dogs. All stents were patent without any evidence of stent displacement, distortion or fracture and intrastent infection or thrombosis as well as intraluminal stenosis or occlusion; the longitudinal and radial shrinkage rates of the stents were less than 2% and 4%, respectively. At one week after implantation, the luminal surface of the stent was rapidly covered by a thin layer of semi-transparent membrane-like structure; at one month after implantation, neointimal formations were seen on most of the luminal surface of the stent which connected with the surrounding intima; at 2 months after implantation, nearly the complete luminal surface of the stent (98.83%) was covered by the neointima, and its thickness reached a peak value (350.00 μm); at 3 to 6 months after implantation, the thickness of the neointima was gradually reduced, its inside diameter was gradually increased to almost the initial size before implantation, and finally, the neointimal surface was covered by a single layer of fully mature endothelial cells. In the neointimal tissues on the luminal surface of the stent, positive staining of smooth muscle α-actin was detected at each time point except one week after immplantaion, while positive staining of vascular endothelial growth factor was detected at any time point after immplantaion. Conclusion: The novel intravascular stent prepared by metal powder injection molding can maintain stable form and structure with fast endothelialization of the luminal surface of stent, and keep long-term patency. It shows favorable structural, physical and chemical stability and biocompatibility, and may have a promising application prospect in clinical practice.