Long-term patency of small-diameter vascular graft made from fibroin, a silk-based biodegradable material.
OBJECTIVE
There is an increasing need for vascular grafts in the field of surgical revascularization. However, smaller vascular grafts made from synthetic biomaterials, particularly those <5 mm in diameter, are associated with a high incidence of thrombosis. Fibroin is a biodegradable protein derived from silk. Silk fibroin from Bombyx mori provides an antithrombotic surface and serves as a scaffold for various cell types in tissue engineering. We evaluated the potential of fibroin to generate a vascular prosthesis for small arteries.


METHODS
A small vessel with three layers was woven from silk fibroin thread. These fibroin-based grafts (1.5 mm diameter, 10 mm length) were implanted into the abdominal aorta of 10- to 14-week-old male Sprague-Dawley rats by end-to-end anastomosis. Polytetrafluoroethylene (PTFE)-based grafts were used as the control. To investigate the origin of the cells in the neointima and media, bone marrow transplantation was performed from green fluorescent protein (GFP) rats to wild-type rats.


RESULTS
The patency of fibroin grafts at 1 year after implantation was significantly higher than that of PTFE grafts (85.1% vs 30%, P < .01). Endothelial cells and smooth muscle cells (SMCs) migrated into the fibroin graft early after implantation and became organized into endothelial and medial layers, as determined by anti-CD31 and anti-alpha-smooth muscle actin immunostaining. The total number of SMCs increased 1.6-fold from 1 month to 3 months. Vasa vasorum also formed in the adventitia. Sirius red staining of the fibroin grafts revealed that the content of collagen significantly increased at 1 year after implantation, with a decrease in fibroin content. GFP-positive cells contributed to organization of a smooth muscle layer.


CONCLUSIONS
Small-diameter fibroin-based vascular grafts have excellent long-term patency. Bone marrow-derived cells contribute to vascular remodeling after graft implantation. Fibroin might be a promising material to engineer vascular prostheses for small arteries.
Enomoto
Soichiro
S
Department of Cardiovascular Medicine, University of Tokyo Graduate School of Medicine, Tokyo, Japan.
Sumi
Makoto
M
Kajimoto
Kan
K
Nakazawa
Yasumoto
Y
Takahashi
Rui
R
Takabayashi
Chiyuki
C
Asakura
Tetsuo
T
Sata
Masataka
M
D020341:Absorbable Implants; D000199:Actins / Q000378:metabolism; D000818:Animals; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging / Q000378:metabolism / Q000601:surgery*; D001027:Aortography; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000295:instrumentation*; D001854:Bone Marrow Cells / Q000378:metabolism; D016026:Bone Marrow Transplantation; D002465:Cell Movement; D003094:Collagen / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism; D005349:Fibroins; D049452:Green Fluorescent Proteins / Q000235:genetics; D008297:Male; D008422:Materials Testing; D023421:Models, Animal; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D011138:Polytetrafluoroethylene; D011474:Prosthesis Design; D051381:Rats; D017207:Rats, Sprague-Dawley; D055647:Rats, Transgenic; D013997:Time Factors; D018615:Ultrasonography, Doppler, Color; D014654:Vascular Patency
D000199:Actins; D003094:Collagen; D005349:Fibroins; D049452:Green Fluorescent Proteins; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D011138:Polytetrafluoroethylene; C485184:enhanced green fluorescent protein; C482288:fibroin, silkworm; C498862:Acta2 protein, rat