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, 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 are involved in a wide variety of cellular events
including cell death and cell adhesion. In this study we investigated the involvement that 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. Our data show a CP-induced change in the activation of the calpain proteolytic pathway, a 10% to 15%
improvement in cell survival when specific calpain inhibitors are utilized in the preservation media, and a slight
decrease in viability when calpain inhibitors are used in the recovery medium. These results appear to support
the multifunctional nature of calpains after CP. That is, calpains may prove to be pivotal in both CIDOCD and
post-thaw cellular adhesion, two limiting steps in the realization of a more successful CP protocol. Ultimately,
this study opens the door for potential improvement of CP efficacy through the modulation of the calpain proteolytic
pathways.
