Acellular Endocardium as a Novel Biomaterial for the Intima of Tissue-Engineered Small-Caliber Vascular Grafts

We aimed to investigate whether acellular endocardium can be used as a useful biomaterial for the intima of engineered small-caliber vascular grafts. Fresh endocardium was harvested from the swine left atrium and was decellularized by digestion with the decellularization solution of Triton X-100 and SDS containing DNase I and RNase A. Surface morphological characteristics and Young's modulus were evaluated. To analyze the effect of mechanical characteristics on cell adhesion, the decellularized endocardium was stiffened with 2.5% glutaraldehyde. Small-caliber vascular grafts were constructed using decellularized endocardium treated with or without glutaraldehyde as the intima. CD34+ cells were seeded onto the luminal surface of the vascular grafts and linked to bioreactors that simulate a pulsatile blood stream. Acellular endocardium had distinct surface morphological characteristics, which were quite different from those of other materials. The compliance of acellular endocardium was higher than that of other materials tested by Young's modulus. CD34+ cells formed a monolayer structure and adhered to the inner face of the acellular endocardium. The glutaraldehyde treatment stiffened the acellular endocardium but had little impact on the surface morphological characteristics or static adhesiveness of the cells. Data from the bioreactor study showed that the detachment of the cells from the surface of glutaraldehyde-treated acellular endocardium increased dramatically when the pressure was equal or higher than 40 mm Hg, while the cells on the untreated acellular endocardium remained well and formed confluent monolayers and tight junctions under the same pressure. Acellular endocardium has distinct structures and mechanical characteristics that are beneficial for CD34+ cell adhesion and retention under dynamic fluid perfusion. Thus, it can be used as a useful biomaterial for the construction of the intima of engineered small-caliber vascular grafts.