Purpose of review: This review outlines the concept of cell-based therapy to restore tissue function, and addresses four key points to consider in cell transplantation: source, surveillance, safety, and site. Whereas each point is essential, additional attention should be given to transplantation sites if cell therapy is going to be successful in the clinic. Various ectopic locations are discussed, and the strengths and weaknesses of each are compared as suitable candidates for cell therapy.
Recent findings: Studies in rodents often demonstrate cell transplantation and engraftment in ectopic sites, with little evidence to suggest why it may also work in humans. For example, transplantation to the subcapsular space of the kidney is often performed in rodents, but has not been a good predictor of clinical success. Recent work has shown that the lymph node may be a good site for transplantation of multiple tissue types, and several reasons are highlighted as to why it should be considered for future studies.
Summary: The use of cell-based therapy in the clinic has been hampered by the lack of appropriate sites for transplantation. The lymph node is a promising alternative for cell transplantation, and offers hope for clinical application.