Thermal Analyses of a Human Kidney and a Rabbit Kidney During Cryopreservation by Vitrification

Abstract

This study focuses on thermal analysis of the problem of scaling up from the vitrification of rabbit kidneys to the vitrification of human kidneys, where vitrification is the preservation of biological material in the glassy state. The basis for this study is a successful cryopreservation protocol for a rabbit kidney model, based on using a proprietary vitrification solution known as M22. Using the finite element analysis (FEA) commercial code ANSYS, heat transfer simulations suggest that indeed the rabbit kidney unquestionably cools rapidly enough to be vitrified based on known intrarenal concentrations of M22. Scaling up 21-fold, computer simulations suggest less favorable conditions for human kidney vitrification. In this case, cooling rates below -100 °C are sometimes slower than 1 °C/min, a rate that provides a clear-cut margin of safety at all temperatures based on the stability of rabbit kidneys in past studies. Nevertheless, it is concluded in this study that vitrifying human kidneys is possible without significant ice damage, assuming that human kidneys can be perfused with M22 as effectively as rabbit kidneys. The thermal analysis suggests that cooling rates can be further increased by a careful design of the cryogenic protocol and by tailoring the container to the shape of the kidney, in contrast to the present cylindrical container. This study demonstrates the critical need for the thermal analysis of experimental cryopreservation and highlights the unmet need for measuring the thermophysical properties of cryoprotective solutions under conditions relevant to realistic thermal histories.

Thermal conductivity of cryoprotective agents loaded with nanoparticles, with application to recovery of preserved tissues and organs from cryogenic storage

“…Ehrlich et. al [ 32 ] has demonstrated the effects of such thermal conductivity variations on thermal analyses of kidney cryopreservation. Fig 4 displays the low variation in thermal conductivity in the temperature range of measurement (-180°C to 0°C) across repeated measurements of M22.…”

A Roadmap to Cardiac Tissue‐Engineered Construct Preservation: Insights from Cells, Tissues, and Organs

“…generated a computational model, based on prior experimental work on the vitrification of a rabbit kidney and on the thermal properties of CPAs, to study the thermal conditions required for the vitrification of a human kidney. [ 73 ] A major issue in kidney vitrification is the high heterogeneity of this organ, which interferes with CPA loading and thermal variation. As such, this model simulates vitrification in a cylindrical container, which allows for a uniform warming when a radiofrequency electrical field is applied.…”

Emerging technologies in organ preservation, tissue engineering and regenerative medicine: a blessing or curse for transplantation?

“…−150 °C) without ice crystal formation, is another promising strategy . Ice avoidance is facilitated by the addition of a mixture of different cryoprotectants with a very rapid but highly controlled cooling rate . Cryopreserved organs and tissues reach the glass transition temperature – about −137 °C for water – where preserved items enter an amorphous or glass‐like conformation, allowing indefinite preservation .…”