Cryopreservation Techniques and Freezing Solutions

Hematopoietic progenitor cell (HPC) products remain viable and capable of engraftment in a transplant recipient when stored in the “liquid state” at either refrigerated or room temperatures for approximately 72 h following collection. Cryopreservation enables long-term storage of HPC products and is used extensively for autologous products collected prior to high-dose chemotherapy (HDT) that are intended for use after treatment to rescue hematopoiesis. Allogeneic products may also be cryopreserved if treatment is delayed due to the donor’s or recipient’s medical condition, the donor’s cells are collected prior to their anticipated use because of donor availability, or more donor cells are obtained than needed and remaining cells are stored for future use. Similarly, allogeneic cord blood products are cryopreserved, prospectively banked, and made available through donor registries. In order for cryopreservation to be an effective tool, when thawed and infused, HPC must be able to regain their ability to proliferate, engraft, and provide the same functional capability prior to cryopreservation. Pre-cryopreservation storage conditions and manipulation procedures, cryoprotectant formulation, freezing rate, long-term storage temperatures, length of time in storage, and thawing conditions all have the potential to affect the quality and engraftment of thawed HPC products.