Liquid or vapor nitrogen is considered the gold standard for the storage of cellular therapy products, ensuring long-term viability and stability. However, contingency planning remains a challenge, as each cryopreserved unit requires an available slot in another tank for redundancy in case of failure. Additionally, most transplant centers in Brazil lack liquid nitrogen storage tanks, and cryopreserved cellular products should be delivered before conditioning begins.

This study aimed to evaluate the impact of short-term transfer of cryopreserved cell therapy units from nitrogen storage to a -80°C freezer, using in vitro assays.

This experimental study included cellular therapy units from individuals referred for autologous stem cell transplantation. Cryopreservation was performed at a single processing facility between 2014 and 2024. Cryopreserved units authorized for discard and aliquoted into at least two bags were included. One bag was thawed immediately after removal from the vapor nitrogen tank, while the paired bag was stored at -80°C for three months before being thawed. The -80°C freezer was continuously monitored, with brief door openings, but temperatures never exceeded -76°C. Thawing was performed using a 37°C water-bath. A resuspension solution (3% human albumin, 2% hydroxyethyl starch 130/0.4, and 2.5% ACD) was added at double the final concentration in a 1:1 volume ratio. Samples were collected for total nucleated cell count, CD34+ immunophenotyping, and colony-forming assays. Data were described using medians with interquartile ranges or percentages, and continuous variables were compared using the non-parametric Wilcoxon paired test.

To date, seven paired bags have been analyzed. The median total nucleated cell count was 292.9 (272.4) × 108 in the liquid nitrogen group and 270.4 (255.9) × 108 in the -80°C group (p = 0.109). Viable CD34+ cell counts were comparable between groups, with medians of 50.4 (102.5) × 106 and 62.5 (50.5) × 106, respectively (p = 0.469). The number of GM colonies did not differ significantly, with 11 (31.5) colonies per 400 CD34+ cells/mL in the nitrogen group and 8 (39.5) colonies per 400 CD34+ cells/mL in the -80°C group (p = 0.313).

The study suggests that -80°C freezers can be a viable short-term storage solution for cryopreserved cellular therapy products, offering a feasible contingency option. This method could significantly reduce costs by lowering operational expenses and infrastructure needs. Furthermore, it could improve access to cellular therapies, especially in under-resourced settings and transplant centers lacking nitrogen storage. This would facilitate the decentralization and broader distribution of transplants across the country, enhancing the availability and delivery of life-saving treatments and contributing to more sustainable healthcare practices. These preliminary results indicate that -80°C freezers may serve as a short-term contingency storage strategy for cell therapy products, provided they are maintained under strict conditions to prevent transient warming events. However, the limited number of thawed units and lack of in vivo validation highlight the need for further research before clinical guidelines can be established.