Systematic review of islet cryopreservation

Figures & data

Figure 1. Flowchart of Cryopreservation. This chart describes the range of temperature, rate of temperature change, and the procedure involved during cryopreservation (adapted from ref#¹⁷).

Figure 2. Slow Rate Cooling Temperature Diagram: Temperature Diagram showing the current standard in cooling rate, which is 0.25°C/min. This slow rate allows the tissue to reach thermal equilibrium, and allows time for water displacement, thus preventing intracellular ice crystal formation. Outlined is the burden of time which occurs due to such slow rates of cooling.

Figure 3. Medium Rate Cooling Temperature Diagram: Temperature diagram showing the significant difference in time when cooling at a rate of 20°C/min. This fast rate of cooling, although untraditional, was found to arrest immunostimulatory agents better than slow freezing.

Figure 4. Fast Cooling Temperature Diagram: Temperature diagram showing the significant difference in time when cooling at a rate of 60°C/min. This fast rate of cooling, although untraditional, was found to arrest immunostimulatory agents better than slow freezing.

Table 1. Cryopreservation Parameters and Suggested Methods: A quick summary of the parameters which had the best outcome for the islets during cryopreservation. Assessment methods include islet viability, glucose sensitivity, and GSIS values after thawing.

Parameter	Method	Reference Number
Cryoprotectant	EPA+DHA+Metformin	40
Cooling Rate	Rapid (50–70°C/min)	27–29
Thawing Rate	Rapid (150–200°C/min)	32
Oxygen Environment	50% during thawing	54
3D Structure	Freeze as individual cells, re-aggregate into spheroids after thaw	51
Encapsulation	1.75% Alginate encapsulation prior to cryopreservation	Unpublished data (Lakey J, et al.)

Rajotte RV, Lakey J, Warnock GL. Adult islet cryopreservation. In: Ricordi C, editor. Methods in cell transplantation. Austin, TX: R. G. Landes Company, 1995. p. 517–524.

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