There is an ever-growing demand for transplantable livers to replace acute and chronically damaged tissues. This demand cannot be met by the current availability of donor organs. Efforts to provide an alternative source have led to the development of organ engineering, a discipline that combines cell biology, tissue engineering and cell/organ transplantation. Over the last several years, techniques to decellularize organs have been developed. We have developed a cadaveric liver decellularization protocol to create a whole-liver scaffold for engineering hepatic grafts in rats. We also demonstrated that adult hepatocytes, endothelial and bile duct cells can be seeded into these scaffolds, remaining viable and providing essential liver functions for up to 10 days. However, the implantations of engineered livers into recipients of rats have been limited to just a few hours due to the inadequate implantation sites and coagulation problems as naked collagen from the graft can be exposed to the blood stream and platelets. 

To solve these problems, we have developed a novel auxiliary partial liver transplantation (APLT) model in rats and an anticoagulant coating method for engineered liver scaffolds. In order to establish an animal model for liver repopulation to be used for transplantation of engineered liver grafts, we used FK506-immune suppressed Nagase analbuminemic rats as recipients. Prior to APLT, the recipient animal was injected with retrorsine and underwent a reduction of portal blood flow at the time of APLT, to create an environment where there was a selective growth advantage to transplanted grafts. The auxiliary partial graft was obtained by resection of the donor median and left lateral lobes, and was heterotopically transplanted into the recipient. Portal-Portal anastomosis and infrahepatic –infrahepatic vena cava anastomosis were performed in an end-to-side manner and bile duct was implanted into the duodenum of the recipient. Graft survival was evaluated over time (up to 28 days) by graft weight, histological evaluation of proliferative markers and serum albumin levels in analbuminemic rats. FK506-based immunosuppression protocol effectively control graft rejection. Transplanted grafts revealed regenerative potential as evaluated by increase of liver mass weight of the donor graft and Ki67 staining analysis. Serum albumin levels were maintained for the duration of the study. Additionally an anticoagulant coating for decellularized liver scaffolds was performed using N-hydroxylsuccinimide functionalized polyethylene glycol (PEG-NHS), which is used to inhibit platelet activation and deposition by blocking surface protein-platelet interactions. PEG-NHS coating in decellularized liver scaffolds reduced significantly (>40%) platelet deposition mainly in major vessels and allowed continued blood perfusion when compare to bared scaffold. Thus, it can be concluded that we have developed a novel APLT model in rats and we have established protocols for the future evaluation of engineered liver grafts with anti-thrombotic activity.