876. Towards Establishing a Heterologous Liver in Rodents

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Top of pageAbstract Liver tissue engineering has been proposed as an approach toward treating several liver diseases as a means to avoid organ transplantation. We have previously reported that stable liver tissues can be engineered and maintained under the kidney capsule by transplanting mature hepatocytes together with extracellular matrix. Because the liver has robust regeneration potential, we investigated if liver tissue engineered at extra-hepatic sites (without portal circulation) would actively regenerate. The present study was aimed to assess graft regenerative activity, and persistence after the induction of active liver regeneration. METHODS: Hepatocytes were isolated from transgenic mice that express a serum marker protein, human alpha1-antitrypsin (hAAT). Two million hepatocytes were then transplanted with EHS gel matrix component under the kidney capsule of isogenic mice. The survival of the transplanted hepatocytes was monitored by histology and periodic measurement of serum hAAT. RESULTS: The hepatocytes were engrafted and maintained for over 20 weeks in all treated mice (n=28). In some of the mice, we confirmed that the grafted hepatocytes developed small pockets of liver tissue because they showed specific characteristics of differentiated hepatocytes composed of hepatocytes in cord structures between the capillaries. We then assessed if the engineered liver tissues maintain their regeneration potential in vivo. We induced an intrinsic mode of liver regeneration (compensatory regeneration) by performing a 2/3 hepatectomy of the naive liver 70 days after hepatocyte transplantation. Two weeks after this procedure, the serum hAAT levels in mice reached 237 ± 18% of the pre-hepatectomy level, establishing similar regeneration activity as that occurred in the naive host livers during this period. The daily increase in liver tissue regeneration reached a peak at day 3 in the engineered liver tissues, showing a similar trend to the naive livers. The regeneration of the engineered livers resolved with restoration of the naive liver to its pre-surgical mass. We also followed the liver tissues long-term after the regeneration, and found that the regenerated liver tissues were stably maintained for over 80 days (length of the experiment). CONCLUSION: The present studies demonstrate that liver tissue, which was recognized as a part of the host naiuml]ve liver in terms of the regeneration profile, could be engineered at a heterologous site that does not have access to the portal circulation.