Stem cell therapies have been quite successful in hematologic disease but the outcomes of clinical studies using stem cells for cardiopulmonary disease have been rather modest.
Explanations for this discrepancy such as the fact that our blood has a high rate of physiologic, endogenous turnover and regeneration whereas these processes occur at far lower rates in the heart and lung. Furthermore, hematopoietic stem cells can be easily identified via cell-surface markers and and engraft. There is far less of a consensus on regenerative cells in the heart and lung and their regenerative potential despite more than 15 years of research.
A major challenge is to fundamentally rethink our current approaches to cardiopulmonary regeneration.