Role of the extracellular matrix in whole organ engineering.

End-stage organ failure is a devastating problem with limited therapeutic options. The definitive treatment is orthotropic transplantation, however, there exists a severe shortage of viable donor organs, and this shortage is worsening with an aging demographic and as the number of new cases of organ failure increases. Patients fortunate enough to receive a transplant are required to receive immunosuppressive therapies and can face transplant rejection. The emerging concept of organ engineering may offer a new hope for these patients. Researchers in the field of regenerative medicine and tissue engineering are using three-dimensional whole organ scaffolds composed of allogeneic or xenogeneic extracellular matrix (ECM) for engineering functional tissue suitable for transplantation. Perfusion decellularization is an approach that generates native ECM scaffolds with intact 3D anatomical architecture and vasculature. Decellularized organs provide the ideal transplantable scaffold with all the necessary microstructure and extracellular cues for cell attachment, differentiation, vascularization, and function. The present manuscript will review the role of the ECM in normal development, the concept of ECM tissue specificity, and the effect of processing methods on eventual clinical outcomes. An overview of existing challenges and future directions will also be discussed.