Serum Apoe as a Reliable Marker to Monitor Graft Function after Hepatocyte Transplantation: 2056

Background: Hepatocyte transplantation is a promising treatment for patients with acute liver failure or metabolic liver diseases. However, major limitations are the lack of reliable noninvasive markers of graft function and the limited engraftment of transplanted cells. Apolipoprotein E (ApoE) is almost exclusively excreted by hepatocytes and is important for lipoprotein metabolism. The ApoE knockout mouse is severely hypercholesterolemic and develops premature atherosclerosis. We established a hepatocyte transplantation model in the ApoE knockout mouse evaluating both serum ApoE as well as lipoprotein profiles as marker of engraftment and function of tranplanted wildtype hepatocytes. Inflammatory injury of transplanted hepatocytes is recognized to be a major cause of initial graft loss. Using this model we also investigated whether pretreatment with Anakinra (anti-IL-1 antagonist) with and without methylprednisolone could improve engraftment of transplanted wildtype hepatocytes. Methods: ApoE-KO mice (B6.129P2-Apoetm1 Unc N11) were transplanted with wildtype hepatocytes isolated from C57BL/6 mice by collagenase perfusion. Controls were transplanted with ApoE-KO hepatocytes. A total of 6 x 106 hepatocytes were transplanted by three seperate intrasplenic injections. Animals were treated before transplantation and daily thereafter for 7 days with either 100 mg/kg/day i.p. Anakinra, alone or in combination with 15mg/kg/day i.p. methylprednisolone. Control mice received sham injections. Weekly blood samples were taken for lipoprotein analysis and quantification of serum ApoE by ELISA. Expression of ApoE mRNA in liver and spleen was quantified by TaqMan RT-PCR. Results: The low level of hepatocyte engraftment (1.5%) did not alter cholesterol or triglyceride lipoprotein profiles in ApoE-KO mice. Repeated hepatocyte transplantations significantly increased liver repopulation. Serum ApoE levels increased two-fold with each hepatocyte infusion. Serum ApoE levels correlated well with hepatic mRNA expression indicating that serum ApoE is a reliable marker of hepatocyte engraftment. Treatment with either Anakinra with and without methylprednisolone did not significantly increase serum ApoE or hepatic mRNA expression. Conclusions: Serum ApoE seems to be a sensitive and reliable marker of engraftment and function of transplanted hepatocytes. Blocking the inflammatory injury of transplanted hepatocytes by Anakinra with or without methylprednisolone does not significantly improve hepatocyte engraftment.