Modification of decellularized vascular xenografts with 8-arm polyethylene glycol suppresses macrophage infiltration but maintains graft degradability.

Because acellular vascular xenografts induce an immunological reaction through macrophage infiltration, they are conventionally crosslinked with glutaraldehyde (GA). However, the GA crosslinking reaction inhibits not only the host immune reaction around the graft but also the graft's enzymatic degradability, which is one of the key characteristics of acellular grafts that allow them to be replaced by host tissue. In this study, we used an 8-arm polyethylene glycol (PEG) to successfully suppress macrophage infiltration, without eliminating graft degradation. Decellularized ostrich carotid arteries were modified with GA or N-hydroxysuccinimide-activated 8-arm PEG (8-arm PEG-NHS), which has a molecular weight of 17 kDa. To evaluate the enzymatic degradation in vitro, the graft was immersed in a collagenase solution for 12 hr. The 8-arm PEG-modified graft was degraded to the same extent as the unmodified graft, but the GA-modified graft was not degraded. The graft was transplanted into rat subcutaneous tissue for up to 8 weeks. Although CD68-positive cells accumulated in the unmodified graft, they did not infiltrate into either modified graft. However, the GA-modified grafts calcified, but the 8-arm PEG-modified graft did not calcify after transplantation. These data suggested that 8-arm PEG-NHS is a promising modification agent for biodegradable vascular xenografts, to suppress acute macrophage infiltration only.