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 (please see Table 1 for symbol definitions), and established a practical approach to measure the value of D̄ 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 D̄ 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.

Cryopreservation of seeds from endangered Brazilian bromeliads - Dyckia brevifolia Baker and D. delicata Larocca & Sobral

“…For this, during the process, cryoprotective substances are used. They act on the cell during the storage period at low temperatures and prevent the formation of intra and extracellular ice, besides preventing possible damage caused by dehydration (Han et al, 2009).…”

Mathematical model formulation and validation of water and solute transport in whole hamster pancreatic islets

“…These models assume that the local contribution of cell-cell and cell-interstitium transport can be approximated by a phenomenological diffusivity parameter in a contiuum model such as the diffusion equation or its porous media analogues. For example, Han et al [14] use the same radially symmetric linear diffusion equation to model mass transport in rat ovaries. However, Levin [6] used diffusion length arguments to show that if cells do not interact and are treated as a “bunch of grapes” for small tissues, equilibration should be solely dependent on the mass transport of single cells in suspension.…”

“…If, however, one keeps the non-interating model but discards the known self-diffusion parameter in lieu of a phenomenological diffusion coefficient (as in Han et al [14]), the challenge here is that the wide range of application conditions needed in cryopreservation protocols, including up to 10 mol/kg CPA concentrations and a nearly 200 °C temperature change in a tissue type that varies greatly in diameter suggests that it is unlikely that a model with a non-geometrically based fitting parameter would be valid in the necessarily wide range of applications. This was the motivation for our approach: that existing physical data for cells and tissues in these widely varying conditions could be adapted to a hybrid model of transport with minimal phenomenological fitting parameters.…”

“…Alternatively, cell-to-cell interactions are ignored and a model based on a diffusion equation with a phenomenological solute diffusivity [11, 12, 13, 14]. These diffusion models may be appropriate for larger and denser tissues with a considerable number of cell layers, and many alternate diffusion-based models have been proposed.…”

Dimethyl Sulfoxide is Less Effective in Immersing Cryopreserved Large Pieces of Tissue: A Rabbit Hind-Limb Model

“…According to this principle, MRS can distinguish different compounds in the frequency axis, and use chemical shift and J-coupling to convert the acquired information into a spectrum, the horizontal axis represents the chemical shift, and the vertical axis peak represents the signal intensity, while the peak of the spectrum The area is proportional to the concentration of the species that produces the peak, which is the basis for structural inference and quantitative analysis of the corresponding compounds by MRS [14]. Although MRS cannot be continuously measured the concentration of the compound, it has the following characteristics: completely non-invasive, accurate positioning, high sensitivity, and quantitative analysis of tissue metabolic changes at the molecular level by imaging technology [15].…”