Vascularized composite allotransplantation and tissue engineering.

For many living with the devastating aftermath of disfiguring facial injuries, extremity amputations, and other composite tissues defects, conventional reconstruction offers limited relief. Full restoration of the face or extremities with anatomic equivalents recently became possible with decades of advancements in transplantation and regenerative medicine. Vascularized composite allotransplantation (VCA) is the transfer of anatomic equivalents from immunologically and aesthetically compatible donors to recipients with severe defects. The transplanted tissues are "composite" because they include multiple types essential for function, for example, skin, muscle, nerves, and blood vessels. More than 100 patients worldwide have benefited from VCA, the majority receiving hand or face transplants. Despite its demonstrated results, the clinical practice of VCA is limited by center experience, public awareness, donor shortage, and the risks of lifelong immune suppression. Tissue engineering (TE) is the generation of customized tissues in the laboratory using cells, biomaterials and bioreactors. Tissue engineering may eventually supersede VCA in the clinic, because it bypasses donor shortage and immune suppression challenges. Billions of dollars have been invested in TE research and development, which are expected to result in a myriad of clinical products within the mid- to long-term. First, tissue engineers must address challenges such as vascularization of engineered tissues and maintenance of phenotype in culture. If these hurdles can be overcome, it is to be hoped that the lessons learned through decades of research in both VCA and TE will act synergistically to generate off-the-shelf composite tissues that can thrive after implantation and in the absence of immune suppression.