Introduction: The clinical efficiency of small-diameter synthetic vascular grafts has been limited by rapid thrombosis and poor patency. We recently achieved excellent patency of the small-diameter decellularized vascular grafts with the inner diameter of 2 mm and the length of 20-30 cm in porcine femoral-femoral crossover bypass model (FF bypass) by modifying the luminal surface with the neointima-inducing peptide modifier[1]. This modification was found to reduce the early stage thrombus formation, which is one of the most important mechanisms. In this study, the neointima formation process in the minipig model was monitored from 1 hr to 1 week, and the cells participated in the luminal endothelialization was identified by scanning electron microscopic (SEM) analysis and histological staining.
Material and Method: Ostrich carotid artery was decellularized by ultra-high hydrostatic pressure treatment. The graft was immersed with 10 mM peptide solution for peptide modification. The peptide-modified and unmodified grafts were transplanted into pig femoral artery as FF bypass and orthotopic transplantation. After transplantation, the luminal surface was observed by SEM. Endothelialization was evaluated by histological staining using HE, vWF, as well as primary antibody against vimentin, CD31, CD105, CD34, and Flk-1.
Results: SEM and HE staining revealed that the luminal surface of the grafts in FF bypass at the center part was completely covered with cells in three days. These cells expressed CD34 and Flk-1, which were progenitor makers. Cellular uptake of acetylated-low density lipoprotein was also confirmed. After orthotopic transplantation for three month, the cell layer expressed vWF, CD31, and CD105 without CD34 and Flk-1 expression.
Discussion: Some researchers have been proposing that the progenitor cells for endothelial cells exist in the peripheral blood. In our experimental results clarified that the endothelial-like progenitor cells were captured onto the luminal surface of peptide-modified grafts in 3 days. These cells formed the matured endothelial cell layer with the histological feature similar to the native blood vessels after three months.
Conclusion: The progenitor cells, which exist in the peripheral blood flow, were captured rapidly by the peptide-modified surface, and it was found that the good patency and suppressed thrombogenicity were achieved due to the rapid endothelialization mechanism.
References:
[1] Mahara A. et al. Biomaterials, 58, 54-62, 2015.