(3e) Regenerative Medicine: From Tissue Engineering to Organ Engineering

The only definitive treatment for end-stage liver disease is orthotopic liver transplantation. Although successful, this procedure is limited by the severe shortage of donor organs with over 27,000 patients dying annually due to lack of the available donor organs, hence, alternative methods to supply viable cells and tissues to patients is urgent. A promising, innovative approach is tissue engineering in which the most appropriate cell populations and biological scaffolds are incorporated and assembled to mimic in vivo structure and physiology of intact organ. Recently, we developed a successful liver decellularization protocol to create transplantable grafts from decellularized whole livers. Decellularized liver matrix (DLM) scaffolds retain a fully intact structure and composition of native organ extracellular matrix (ECM) as well as vascular network, and can be repopulated with hepatocytes (the cells that carry out most of the liver’s primary functions), demonstrating function in vitro and in vivoafter transplantation. Although we have shown successful transplantation of the recellularized grafts in the short term (8 h), long-term survival of recipients was limited by occurrence of thrombosis due to contact of blood with the naked ECM scaffold upon transplantation. Therefore, a DLM graft that is thromboresistant is necessary to extend the transplantation time and evaluate therapeutic benefits of the implant in animal models of liver failure.

The long-term goal is to engineer a transplantable liver graft for curing and treating relevant liver diseases. The objective is to generate a thromboresistant and functional liver graft by forming a heparin-coated surface in the DLM via layer-by-layer (LbL) self-assembly technique and repopulating with primary hepatocytes and microvascular endothelial cells. The central hypothesis is that the heparin immobilization of the DLM scaffold will extend survival of the graft recipients by blocking thrombosis in vivo and allow for functional evaluation of the grafts in animal models of liver failure in the long-term. The rationale is that heparin anticoagulant surface modification of the decellularized matrix will greatly aid in preventing thrombosis during blood perfusion while allowing for repopulation with cells in vitro; these findings will lead to create a desirable tissue-engineered liver that enables to support long-term recipient survival after transplantation.