L-carnitine as an antioxidant to improve the efficiency of cord blood hematopoietic progenitor cell cryopreservation

The cryopreservation of hematopoietic progenitor cells (HPCs) derived from cord blood is a critical component of regenerative medicine and transplantation, ensuring the long-term availability of viable cells for therapeutic use. However, oxidative stress during the freezing and thawing process can compromise cell survival and function, highlighting the need to improve cryopreservation protocols. Purpose. This study aimed to evaluate the effectiveness of L-carnitine, an antioxidant, when added to DMSO-based cryoprotective solutions in enhancing the post-thaw survival and viability of human cord blood-derived HPCs under in vitro conditions simulating transfusion. Materials and methods. Cord blood-derived nucleated cells, including CD45dimCD34+ HPCs, were collected after normal deliveries (n = 5). Cryopreservation was performed using DMSO at concentrations of 2.5 %, 5 %, and 7.5 %, supplemented with L-carnitine in the range of 1-50 mM. Cell viability was assessed immediately after thawing and following in vitro simulated transfusion (incubation in Hanks’ solution at 37 °C for 1 hour) using 7-aminoactinomycin D (7-AAD) staining and flow cytometry. Results. The addition of L-carnitine to the cryopreservation medium significantly increased the viable yield of CD34⁺ cells, particularly at concentrations of 15-20 mM, both immediately after thawing and following incubation at physiological temperature. These results indicate that L-carnitine confers protective effects against oxidative stress-induced damage during cryopreservation. Conclusion. The results obtained indicate that L-carnitine increases the efficiency of cryopreservation of human cord blood hematopoietic progenitor cells, contributing to an increase in their preservation and viability. The determined optimal cryoprotective medium may be useful for the development of new and improvement of existing protocols for the preservation of human cord blood-derived cellular components.