Implantation study of small-caliber "biotube" vascular grafts in a rat model.

We developed autologous vascular grafts, called "biotubes," by simple and safe in-body tissue architecture technology, which is a practical concept of regenerative medicine, without using special sterile conditions or complicated in vitro cell treatment processes. In this study, biotubes of extremely small caliber were first auto-implanted to rat abdominal aortas. Biotubes were prepared by placing silicone rods (outer diameter 1.5 mm, length 30 mm) used as a mold into dorsal subcutaneous pouches in rats for 4 weeks. After argatroban coating, the obtained biotubes were auto-implanted to abdominal aortas (n = 6) by end-to-end anastomosis using a custom-designed sutureless vascular connecting system under microscopic guidance. Graft status was evaluated by contrast-free time-of-flight magnetic resonance angiography (TOF-MRA). All grafts were harvested at 12 weeks after implantation. The patency rate was 66.7 % (4/6). MRA showed little stenosis and no aneurysmal dilation in all biotubes. The original biotube had wall thickness of about 56.2 ± 26.5 μm at the middle portion and mainly random and sparse collagen fibers and fibroblasts. After implantation, the wall thickness was 235.8 ± 24.8 μm. In addition, native-like vascular structure was regenerated, which included (1) a completely endothelialized luminal surface, (2) a mesh-like elastin fiber network, and (3) regular circumferential orientation of collagen fibers and α-SMA positive cells. Biotubes could be used as small-caliber vascular prostheses that greatly facilitate the healing process and exhibit excellent biocompatibility in vascular regenerative medicine.