In Vivo Construction Of Small-Caliber Blood Vessels By Small Intestinal Submucosa Conduits And Bone Marrow Cells

Objective: To investigate the feasibility of in vivo one-stage construction of blood vessels using small-caliber vascular conduits made of porcine small intestinal submucosa and bone marrow cells.Materials and Methods: The SIS films were agglutinated into small-caliber (D=3mm) conduits by a mixed solution of collagen and chondroitin sulfate, and crosslinked by carbodiimide afterwards. Then the burst pressure measurement, in vitro hemolysis test and cytotoxicity test were performed to examine the mechanical strength and biocompatibility of the scaffolds. The water contact angles and in vitro coagulation time were also tested to assess the anticoagulation capability of SIS conduits. In the animal experiments, traditional sutured SIS conduits, agglutinated and crosslinked SIS conduits, and the later combined with autologous bone marrow cells were implanted to replace the defects of rabbit common carotid arteries respectively (L=15mm). After the operation, periodic color Doppler was applied to detect the patency, and histological HE stain, Masson stain as well as immunohistochemistry were performed to observe the tissue remodeling. Through the group comparision, the performance of SIS conduits and development of applied cells and scaffolds could be evaluated.Results:The burst pressure of the agglutinated and crosslinked SIS scaffolds was 22.1kPa at moist status. The hemolysis rate was 1.4%, and the cytotoxisity gradation was 0~1. Compared with the untreated SIS, the water contact angle of crosslinked SIS was significantly decreaced, and coagulation time was obviously prolonged ( p<0.05). After 2 months'implantation of conduits to replace the common carotid arteries of rabbits, the patency rate of the agglutinated and crosslinked ones was 86.7% (13/15), which was higher than that of the sutured ones (33.3%, 5/15, p<0.05). Among the patent vessels, the rate of aneurysmal dilatation was high (100% and 38.5%) in the sutured conduits and agglutinated and crosslinked ones, while none happened in the conduits combined with bone marrow cells. Complete and confluent endothelia could form while the ingrowth of vascular smooth muscle cells in SIS tissue could be observed in all of the harvasted patent vessels at 1 mon postoperatively; and the SIS degraded with the increase of vascular smooth muscle cells at 2 mon postoperatively. No obvious inflammatory reaction or angiorrhexis occurred in all the scaffolds. And the immunohistochemistry examination demonstrated that the intimal layer was composed of smooth and intact blood vessel endothelium, and the vessel wall was ingrown by regular vascular smooth muscle cells.Conclusion: The agglutination and crosslink could improve the performance of SIS as vascular scaffolds;The prepared SIS conduits combined with autologous bone marrow cells replace the defects of small-caliber vessels in one stage, maintain favourable patence and morphous, and form biological vessels gradually.