Cell-based cardiovascular repair--the hurdles and the opportunities.

Cardiovascular cell therapy offers the first real potential to treat the underlying injuries associated with cardiac and vascular disease. By delivering appropriate exogenous cells to an injury site, the potential exists to mitigate injury or even to begin to reverse damage. Based on their inordinate pre-clinical promise as myogenic or angiogenic precursors, skeletal myoblasts and bone marrow or blood-derived mesenchymal and hematopoietic progenitor cells have all rapidly moved from bench to early clinical studies. From these parallel paths we are learning a number of useful lessons and have begun to visualize the hurdles to be overcome as we move these therapies forward. It is now obvious that cell-based cardiac and vascular repair are feasible-both early and later in the disease process. In fact, cell therapy may offer an unparalleled opportunity for improvement to millions of individuals living with cardiovascular disease. However, many questions about the technology remain. The mechanisms associated with cardiovascular repair remain unclear. Whether a best cell type, delivery method, or route of administration exists is unknown. And, whether cellbased disease prevention is feasible is still unanswerable. Now is the time to delve deeply into the questions of cell-based myocardial and vascular repair-even as we cautiously proceed clinically. Only by understanding these issues will we be able to decrease unanticipated clinical effects and to fulfill the potential promise of the most exciting opportunity yet to treat CVD. As we do so, we must prevent uncontrolled, poorly planned studies and until we understand cell therapy's potential, we must limit "too good to be true" promises. Only by addressing unanswered questions, carefully limiting our promises, and rigorously performing pre-clinical and clinical studies can we provide the surest opportunity for safely moving the field forward.