Native macrophages genetically modified to express heme oxygenase 1 protect rat liver transplants from ischemia/reperfusion injury

We investigated whether native macrophages overexpressing heme oxygenase 1 (HO-1) could protect rat orthotopic liver transplant (OLT) against cold ischemia/reperfusion injury (IRI). Livers from Sprague-Dawley rats were stored at 4°C in University of Wisconsin solution for 24 hours, and then they were transplanted into syngeneic recipients. Bone marrow-derived macrophages (BMMs) that were transfected ex vivo with heme oxygenase 1 adenovirus (Ad-HO-1), β-galactosidase adenovirus (Ad-β-gal), or HO-1 small interfering RNA (siRNA) were infused directly into the OLT before reperfusion. Controls were OLT conditioned with unmodified or scrambled siRNA-transfected cells. The transfer of Ad-HO-1/BMMs increased the survival of OLT to 100% (versus 40%-50% for controls) and decreased serum alanine aminotransferase levels and histological features of hepatocellular damage. In contrast, an infusion of macrophages transfected with HO-1 siRNA/Ad-β-gal failed to affect IRI. Gene therapy-induced HO-1 suppressed toll-like receptor 4 expression, decreased expression of proinflammatory tumor necrosis factor α, interleukin-1β, monocyte chemoattractant protein 1, and chemokine (C-X-C motif) ligand 10, and attenuated endothelial intercellular cell adhesion molecule 1 expression with resultant diminished OLT leukocyte sequestration. Although Ad-HO-1/BMMs decreased the frequency of apoptotic cells positive for terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and ameliorated caspase-3 activity, the expression of interleukin-10 and antiapoptotic B cell lymphoma 2/B cell lymphoma extra large increased in well-functioning OLT. Thus, the transfer of native macrophages transfected ex vivo with HO-1 can rescue rat iso-OLT from IRI. Our study validates a novel and clinically attractive concept: native macrophages transfected ex vivo with the antioxidant HO-1 can be applied at the time of transplantation to mitigate otherwise damaging antigen-independent liver inflammation and injury resulting from the peritransplant harvesting insult. If this new, refined strategy is proven to be effective in allo-OLT recipients, it should be considered in clinical settings to increase the supply of usable donor organs and ultimately improve the overall success of liver transplantation