Measurement of the apparent diffusivity of ethylene glycol in mouse ovaries through rapid MRI and theoretical investigation of cryoprotectant perfusion procedures

Abstract

Successful organ cryopreservation will significantly benefit human health and biomedical research. One of the major challenges to this accomplishment is the need for optimization of cryoprotectant agent (CPA) perfusion procedures that involve highly complicated mass transfer processes in organs. The diffusivity of CPA is of critical importance for designing perfusion procedures to minimize the associated toxicity and osmotic damage. However, to date there have been no attempts to measure the CPA diffusivity in organs. In this study, we established a simple CPA diffusion model for relatively small organs, e.g., mouse ovaries, defined the apparent diffusivity ( D ¯ ) of CPA for these organs, and established a practical approach to measure the value of D ¯ through magnetic resonant imaging (MRI). Using rapid MRI techniques and water saturation analyses, the distribution of ethylene glycol (EG) concentration in the centric cross-section of mouse ovaries was measured at a series of time points during perfusion, and these data were fit to the integral form of the mass transfer equation in the established model. These fits resulted in a value of D ¯ for EG in mouse ovaries of 6.1 ± 1.4 × 10 −7 cm 2/s (mean ± SD). Based on these results, we proposed a modified perfusion procedure that may improve the survival of small organs or thin tissues during equilibrium cooling processes and assessed its efficiency through theoretical analyses.