PERSPECTIVE: Advances in glycerol-free and low-glycerol cryopreservation of red blood cells

This review recounts the advances in cryopreservation technologies of red blood cells (RBC). The limitations of traditional glycerol-based methods and the latest developments in cryopreservation with no or less glycerol are elaborated. Although the use of glycerol at high-concentrations effectively prevents ice crystal formation, the associated osmotic stress damages RBC. Moreover, the cumbersome and time-consuming deglycerolization process not only increases operational costs, but also poses the risks of contamination and additonal cell damage, thereby limiting the application of frozen blood for emergency situations. To overcome these challenges, novel strategies have focused on rapid freezing with no or less glycerol, new permeable cryoprotectants and the synergistic use of non-permeable macromolecular/saccharide protectants (such as trehalose and hydroxyethyl starch). These approaches aim to achieve more efficient and safer preservation through multi-faceted protective mechanisms via the reduction of ice crystal damage, osmotic stress and oxidative damage. New strategies demonstrate significant advantages in streamlining processes (eliminating or simplifying deglycerolization steps), improving cell recovery and quality (low hemolysis) and enhancing in vivo efficacy. However, challenges such as long-term storage stability, scale-up production costs, standardization and regulatory approval remain critical issues to be addressed before clinical translation can be realized. Future research needs to focus on optimizing cryoprotectant formulations, elucidating molecular mechanisms, establishing a standardized quality control system and clinical validation, thereby revolutionizing blood inventory management.