Evaluation of a xeno-free protocol for long-term cryopreservation of cord blood cells

Cord blood is regarded as a powerful source for adult stem cells. Cord blood transplants have been used successfully to treat children and adults in autologous and allogeneic settings. Nevertheless, in many cases, the clinically relevant cell number (CD34+ cells and total leukocytes) is a limiting factor. To enable standardized cell banking and future in vitro expansion of adult stem/progenitor cells, elimination of serum, which inevitably differs from lot to lot and donor to donor, is highly desirable. Here, we demonstrate the feasibility of a xeno-free, chemically defined cryopreservation procedure for cord blood-derived cells over a period of 1 year. Cell recoveries with respect to retrieval of clinically relevant CD34+ cells, colony-forming units, and in vitro cultures of erythroid progenitor cells under standardized conditions were analyzed after 1 week or 1 year of cryopreservation and found to be very high and similar to the samples before freezing. The established xeno-free procedure is an important step toward using the full potential of adult stem cells from cord blood, enabling the elimination of serum-derived factors negatively influencing proliferation, differentiation, and survival of hematopoietic stem cells.