Toxicity Measurements for Human-Scale Organ Vitrification CPAs

Vitrification is a cryopreservation method that employs high concentrations of cryoprotective agents (CPA) to preserve organ viability indefinitely. Achieving vitrification typically requires CPA concentrations of 8–9M to effectively permeate tissues or organs; however, these levels are associated with significant toxicity. The CPA toxicity rate (k) quantifies the rate at which CPAs induce cytotoxic effects, influenced by CPA formulation, concentration and temperature. CPAs such as VM3 (8.46M), M22-PVP (9.34M) and M22 (9.35M) are currently under investigation for large organ cryopreservation. VM3 has been applied in kidney slice vitrification, while M22-PVP and M22 have been applied in rabbit kidney vitrification. This study evaluates the toxicity of these scalable CPAs at 4◦C using rat kidney tissue slices. The slices were progressively exposed to increasing concentrations of VMP (a transitional CPA) to reach the final concentration, followed by exposure to VM3, M22-PVP or M22 for varying durations. Changes in tissue viability were measured, and toxicity rates were subsequently determined. VM3 exhibited the lowest toxicity rate (k = 0.007958min−1) compared to M22-PVP (k = 0.01755min−1) and M22 (k = 0.02339min−1). The findings from this study, combined with future research on the temperature dependence of CPA toxicity, will drive the development of long-term human kidney banking for transplantation, enhancing donor-recipient matching, promoting equitable access, refining patient preparation and tolerance induction protocols, optimizing organ utilization and ultimately improving survival outcomes.