Albumin-based solution is the ideal post-thawing suspension medium for cord blood hematopoietic stem cells: A stability and proliferative evaluation.

Background: Cryopreservation and thawing protocols represent key factors for the efficacy of cellular therapy products, such as hematopoietic stem cells (HSCs). While the HSC cryopreservation has already been standardized, the thawing procedures have been poorly studied. This study aimed to evaluate the thawing and washing protocol of cord blood (CB) derived HSCs or the HPC(CB), by selecting the optimal thawing solution and determining CD34+ cells' stability over time.

Study Design And Methods: Seven cryopreserved CB products were thawed, washed, and resuspended in three different solutions (10% Dextran40 in NaCl equally prepared with 5% human albumin; 5% human albumin in PBS/EDTA; and normal saline) and stored at 4°C (±2°C). Mononuclear cell (MNC) count, CD45+/CD34+ cell enumeration, and cell viability were tested at 0, 1, 2, 4, 6, 8, 12, 24, 36, and 48 h. The protocol with the selected solution was further validated on additional 10 CB samples. The above parameters and the colony-forming unit (CFU) assay were analyzed at time points 0, 2, 4, 6, and 8 h.

Results And Discussion: The results showed that the 5% human albumin was the most suitable thawing solution. MNCs were stable up to 4 h (p = 0.009), viable CD45+ cells were unstable even at 2 h (p = 0.013), and viable CD34+ cells were stable until 6 h (p = 0.019). The CFU assay proved the proliferative potential up to 8 h, although significantly decreased after 4 h (p = 0.013), and correlated with the viable CD34+ cell counts. We demonstrated that the post-thawed and washed HPC(CB) using 5% human albumin is stable for up to 4 h.