Calpain activation following cryopreservation: An initial investigation into their roles in cell death and cell adhesion

Recent focus of the phenomenon of cryopreservation-induced delayed-onset cell death (CIDOCD) has been linked to molecular-based cellular responses. Current literature suggests that along with caspases, the classical apoptotic proteases, additional proteases such as calpains, may also play integral roles in cell death. Although the regulation and activation of calpains is not fully understood, it is becoming increasingly clear that they perform multifaceted tasks within a cell. They have been implicated in initiating or progressing a wide variety of events including cell death and cell adhesion.; In this study we investigated for the first time the involvement the calpain family of proteases has on cell death and cell adhesion during cryopreservation (CP) and the subsequent recovery period. It was hypothesized that a CP-dependent activation of the calpain cascade would contribute to the activation and progression of the events associated with CIDOCD, and by modulating this activity more successful CP could be achieved. Additionally, we began an initial investigation into the relationship between the calpain and caspase proteolytic pathways during CIDOCD.; Our data show a CP-induced change in the activation of the calpain proteolytic pathway, a 10 to 20% improvement in cell survival when specific calpain inhibitors are utilized, and a small, 3 to 4% decrease in viability when calpain inhibitors are used in the recovery medium. These results appear to support the multipurpose nature of calpain activity. That is, calpains may prove to be pivotal in both CIDOCD and post-thaw cellular adhesion, two limiting steps in the realization of a successful CP protocol. Ultimately, this study opens the door to improving CP efficacy through the modulation of the calpain proteolytic pathways.