Cell-based therapies: from basic biology to replacement, repair, and regeneration.

A series of meetings in the last 6 months has afforded an extraordinary opportunity to assess the progress that has been made in the development of cell-based therapeutic approaches and the issues that still need to be addressed. Even though real progress has been made, it has become clear that the key to success will come from a better understanding of the basic biology so as to be able to deliver the right biological signals at the right place and at the right time. Beyond the basic biology, there are some other key issues. These include the selection of cell source, the development of "smart", instructive biomaterials that can be used to deliver the biological signals, and the development of bioreactors for the expansion of cells and the growth of tissues, ones that can be scaled up for clinical studies. Tissue engineering and regenerative medicine, though still very much in a fledgling state, continues to offer the promise to address clinical needs where today there are no treatment options available. To do this, however, will require a better understanding of the biology and the development of key technologies. Long-term clinical therapies and treatments must move beyond the replacement of tissues and organs to the harnessing of the intrinsic repair and regenerative potential of the human body.