Analysis of HPC and HSC post-thaw viability, clonogenic capacity, and proliferative potential after cryopreservation in comercially available media

The recent availability of a commercially-available media formulation (CryoStor^TM) designed for optimal long-term HSC storage prompted us to analyze HPC and HSC subset viability, clonogenic capacity, and proliferative potential of RBC-depleted CB samples after cryopreservation using these media formulations, compared with using our standard storage media formulation. Flow cytometric analysis indicated slightly improved viability of CD45+ CD34+ hematopoietic progenitor cells and CD45+ CD34+CD38-CD90+ hematopoietic stem cells after cryopreservation using CryoStor 5, compared to a standard 5% DMSO and 3% Hetastarch-containing cryopreservation media. The ability of the frozen/thawed cells to proliferate in culture in response to SCF, FLt-3 and TPO, as measured by BrDU uptake after 48 hrs, appears to be decreased after cryopreservation in the commercially available media (n=1), although further evaluation is needed. The clonogenic capacity after cryopreservation in both media formulations appears similar, with 94 CFU/10⁵ cells in CryoStor 5, compared to 85 CFU/10⁵ cells in standard cryopreservation media (n=1). Even though there may only be a small difference, if any in the viability and recovery of cells with a hematopoietic progenitor and stem cell phenotype between the two freezing formulations, it may be advantageous to use the commercially available media for cryopreservation and storage of HPC products intended for transplant. Future experiments will extend the evaluations to more samples and include a further evaluation of the proliferative capacity of progenitor and stem cells cryopreserved using the two formulations.