Blockade of endothelial Gi protein enhances early engraftment in intraportal cell transplant to mouse liver.
ABSTRACT The limited availability of liver donors and recent progress in cell therapy technologies has centered interest on cell transplantation as a therapeutic alternative to orthotopic liver transplant for restoring liver function. Following transplant by intraportal perfusion, the main obstacle to cell integration in the parenchyma is the endothelial barrier. Transplanted cells form emboli in the portal branches, inducing ischemia and reperfusion injury, which cause disruption of endothelial impermeability and activate the immune system. Approximately95% of transplanted cells fail to implant and die within hours by anoikis or are destroyed by the host immune system. Intravascular perfusion of Bordetella pertussis toxin (PTx) blocks endothelial G(i) proteins and acts as a reversible inducer of actin cytoskeleton reorganization, leading to interruption of cell confluence in vitro and increased vascular permeability in vivo. PTx treatment of the murine portal vascular tree 2 h before intraportal perfusion of embryonic stem cells facilitated rapid cell engraftment. By 2 h post-perfusion, the number of implanted cells in treated mice was more than five-fold greater than in untreated controls, a difference that was maintained to at least 30 days post-transplant. We conclude that prior to cell transplant, PTx blockade of the Gi protein pathway in liver endothelium promotes rapid, efficient cell implantation in liver parenchyma, and blocks chemokine receptor signaling, an essential step in early activation of the immune system.