Xenotransplantation Literature Update September–October, 2005

During the period of September to October, 2005, six reviews of aspects of xenotransplantation were published [1–6]. Hammerman [2] reviewed studies that addressed the possibility of growing new organs in situ by implanting embryonic organs (anlagen). Kidney and pancreas anlagen, when transplanted into animal hosts, were shown to undergo differentiation and growth and could subsequently be transplanted into a final recipient. O’Connell [5] suggested that the thrombotic microangiopathy described by others might be the next major hurdle for xenotransplantation. Although hyperacute rejection (HAR) has been controlled by the use of geneticallymodifiedpig donors, thrombotic microangiopathy occurred when organs of a1,3-galactosyltransferase gene-knockout pigs were transplanted into baboons, possibly associated with major incompatibilities between species-specific clotting factors and thromboregulatory molecules present on pig endothelial cells. The author concluded that further genetic modifications should be performed on organ-source pigs, with the aim that their endothelial cells would lack Galactosea1,3Galactose (Gal) but also express both human complement-regulatory and thromboregulatory molecules [5]. Van de Kerkhove et al. [6] reviewed their experience using their Academic Medical Center Bioartificial Liver device containing porcine hepatocytes to bridge patients with acute liver failure to orthotopic liver transplantation. The Phase 1 study showed the in vitro functionality and the in vivo safety of the bioartificial liver in 12 patients.