Effect of long-term cryopreservation at −80 °C on the viability and recovery of peripheral blood stem cells

Objectives: We aimed to determine the effects of long-term storage and the presence of other cells on the viability and recovery of cryopreserved PBSCs. Methods: Autologous and allogeneic PBSC samples (n = 115) were cryopreserved at −80 °C in a mechanical freezer without controlled-rate freezing. CD34+ cell viability and recovery were evaluated after storage for up to 60 months using flow cytometry. We also evaluated the effect of other blood cells on the cryopreservation of CD34+ cells. Results: The viability and recovery of CD34+ cells stored for >24 months decreased. Furthermore, samples containing ≥10% granulocytes showed a decrease in the number of viable CD34+ cells. Conclusions: Our findings suggest that PBSCs can be stored at −80 °C in a mechanical freezer without controlled-rate freezing for up to 24 months. High granulocyte content affects the viability of CD34+ cells during cryopreservation.