Potency, Proliferation and Engraftment Potential of Stem Cell Therapeutics: The Relationship between Potency and Clinical Outcome for Hematopoietic Stem Cell Products

This review describes why potency is important and how potency can be measured to release stem cell cellular therapeutic products for transplantation into patients. Particular attention is paid to umbilical cord blood as a stem cell product and the misconception that potency must correlate with clinical outcome. The case is made that present day tests and assays used in the cord blood industry provide only basic cell characterization. Although these tests and assays may correlate with time to engraftment as a clinical outcome, they do not measure the potency of the stem cells that are responsible for, and correlate with, the engraftment response. It is suggested that present cell therapeutic product characterization be supplemented with more advanced assays that incorporate accepted concepts and principles of potency testing and can actually measure stem cell potency in accordance with regulatory requirements.