Stem cells in CNS and cardiac regeneration.

The central nervous system (CNS) and the heart muscle regenerate poorly after injury, yet evidence is mounting that both harbor cells capable of rebuilding neural and cardiac tissue. The reason for the poor regenerative response of CNS tissue and myocardium must therefore lie in the nature of the injury environment, which promotes fibrosis over regeneration. Strategies for regenerating these tissues thus rely on overcoming the fibrotic response by filling lesions with tissue-specific regeneration-competent cells that replace or rescue dying cells, or by activating endogenous regeneration-competent cells that do likewise. There has also been considerable excitement about the possibility of transplanting bone marrow cells into CNS or cardiac lesions to repair them, because bone marrow cells have been reported to be pluripotent. In this chapter, contemporary evidence for the existence of regeneration-competent cells in the CNS and heart is discussed, as well as attempts to use these cells and bone marrow cells to reconstitute new tissue.