Cell Damage during Thawing of Cryopreserved MRC-5 Cell Suspensions Sean McManus, Villanova University
The MRC-5 cell line (human lung fibroblast) is the primary cell line used in producing the chickenpox vaccine for global distribution. Cell suspensions must be cryopreserved for purposes of distribution, quality control, inventory control, and maintaining a consistent supply of cells. The cryopreservation process can result in intracellular ice formation (IIF), which causes irreversible cell damage. With some cooling rates, a consequence of IIF is cell darkening. However, during the thawing process there was evidence of cell darkening, which was previously thought to only be characteristic of cells incurring intracellular ice during freezing. This darkening, along with drastic cellular expansion, raises questions regarding whether or not there is a loss in cell viability during the thawing process. In the present study, the effect of rapid warming following various cooling rates (1-120° C/min) in suspensions of MRC-5 cells was investigated using a high-speed video cryomicroscopy system. Cells were cooled with and without the cryoprotectant dimethyl sulfoxide (DMSO) to -60° C and rapidly warmed at 120° C/min to 4° C. Results suggest that cell darkening during thawing varies depending on the cooling rate used to freeze the cells.