Cryopreservation of umbilical cord blood with a novel freezing solution that mimics intracellular ionic composition

Cryopreservation protocols have remained relatively unchanged since the first umbilical cord blood banking program was established. This study evaluated the preservation efficacy of a novel intracellular-like cryopreservation solution (CryoStor, BioLife Solutions, Inc.), the rate of addition of two cryopreservation solutions to cord blood units (CBUs), and reduced final dimethyl sulfoxide (DMSO) concentration of 5%.

Split-sample CBUs were cryopreserved with either an in-house 20% DMSO-based cryopreservation solution or CryoStor CS10 at a rate of 1 mL/min (n = 10; i.e., slow addition) or as a bolus injection (n = 6; i.e., fast addition). Infrared images of exothermic effects of the cryopreservation solutions were monitored relative to the rate of addition. Prefreeze and postthaw colony-forming unit assays, total nucleated cells, and CD34+ cell counts were compared.

Maximum temperature excursions observed were less than 6°C, regardless of the rate of solution addition. Fast addition resulted in peak excursions approximately twice that of slow addition but the magnitude and duration were minimal and transient. Slow addition of CryoStor CS10 (i.e., final concentration ≤ 5% DMSO) resulted in significantly better postthaw CD34+ cell recoveries; no other metrics were significantly different. Fast addition of CryoStor resulted in similar postthaw metrics compared to slow addition of the in-house solution.

Slow and fast addition of cryopreservation solutions result in mean temperature changes of approximately 3.3 to 4.45°C. Postthaw recoveries with CryoStor were equivalent to or slightly better than with the in-house cryopreservation solution. CryoStor also provides several advantages including reduced processing time, formulation consistency, and reduced DMSO in the frozen product (≤ 5%).