Osmotic parameters of red blood cells from umbilical cord blood

The transfusion of red blood cells from umbilical cord blood (cord RBCs) is gathering significant interest for the treatment of fetal and neonatal anemia, due to its high content of fetal hemoglobin as well as numerous other potential benefits to fetuses and neonates. However, in order to establish a stable supply of cord RBCs for clinical use, a cryopreservation method must be developed. This, in turn, requires knowledge of the osmotic parameters of cord RBCs. Thus, the objective of this study was to characterize the osmotic parameters of cord RBCs: osmotically inactive fraction (b), hydraulic conductivity (L_p), permeability to cryoprotectant glycerol (P_glycerol), and corresponding Arrhenius activation energies (E_a). For L_p and P_glycerol determination, RBCs were analyzed using a stopped-flow system to monitor osmotically-induced RBC volume changes via intrinsic RBC hemoglobin fluorescence. L_p and P_glycerol were characterized at 4 °C, 20 °C, and 35 °C using Jacobs and Stewart equations with the E_a calculated from the Arrhenius plot. Results indicate that cord RBCs have a larger osmotically inactive fraction compared to adult RBCs. Hydraulic conductivity and osmotic permeability to glycerol of cord RBCs differed compared to those of adult RBCs with the differences dependent on experimental conditions, such as temperature and osmolality. Compared to adult RBCs, cord RBCs had a higher E_a for L_p and a lower E_a for P_glycerol. This information regarding osmotic parameters will be used in future work to develop a protocol for cryopreserving cord RBCs.