Toward development of an implantable tissue engineered liver.

Hepatocyte transplantation on implantable devices is a tissue engineering approach to improve the treatment of liver disease and the efficacy of ex vivo gene therapy. Diverse physiological functions and high metabolic activity of the liver represent significant challenges to engineering implantable devices that provide long-term hepatic support. Liver tissue engineering research has explored alternatives to direct hepatocyte injection that include hepatocyte attachment to microcarriers, encapsulation and transplantation on biodegradable polymer scaffolds. Successful function of hepatocytes transplanted on implantable devices in animal models has been documented by production of albumin and other liver-specific markers, and clearance of bilirubin and urea metabolites. Strategies used to achieve these successes are reviewed, with particular emphasis on biodegradable polymer scaffolds, and two areas of investigation that may improve the function of implantable tissue engineered liver devices are highlighted.