Suprazero cooling conditions significantly influence subzero permeability parameters of mammalian ovarian tissue

Abstract

To model the cryobiological responses of cells and tissues, permeability characteristics are often measured at suprazero temperatures and the measured values are used to predict the responses at subzero temperatures. The purpose of the present study was to determine whether the rate of cooling from +25 to +4 degrees C influenced the measured water transport response of ovarian tissue at subzero temperatures in the presence or absence of cryoprotective agents (CPAs). Sections of freshly collected equine ovarian tissue were first cooled either at 40 degrees C/min or at 0.5 degrees C/min from 25 to 4 degrees C, and then cooled to subzero temperatures. A shape-independent differential scanning calorimeter (DSC) technique was used to measure the volumetric shrinkage during freezing of equine ovarian tissue sections. After ice was induced to form in the extracellular fluid within the specimen, the sample was frozen from the phase change temperature to -50 degrees C at 5 degrees C/min. Replicate samples were frozen in isotonic medium alone or in medium containing 0.85 M glycerol or 0.85 M dimethylsulfoxide. The water transport response of ovarian tissue samples cooled at 40 degrees C/min from 25 to 4 degrees C was significantly different (confidence level >95%) from that of tissue samples cooled at 0.5 degrees C/min, whether in the presence or absence of CPAs. We fitted a model of water transport to the experimentally-derived volumetric shrinkage data and determined the best-fit membrane permeability parameters (L(pg) and E(Lp)) of equine ovarian tissue during freezing. Subzero water transport parameters of ovarian tissue samples cooled at 0.5 degrees C/min from 25 to 4 degrees C ranged from: L(pg) = 0.06 to 0.73 microm/min.atm and E(Lp) = 6.1 to 20.5 kcal/mol. The corresponding parameters of samples cooled at 40 degrees C/min from 25 to 4 degrees C ranged from: L(pg) = 0.04 to 0.61 microm/min.atm and E(Lp) = 8.2 to 54.2 kcal/mol. Calculations made of the theoretical response of tissue at subzero temperatures suggest that the optimal cooling rates to cryopreserve ovarian tissue are significantly dependent upon suprazero cooling conditions.

Permeability Characteristics of Ovine Primordial Follicles Calculated with Two Parameter Kedem-Katchalsky Formulation

“…28 Interestingly, the rate at which equine and macaque ovarian tissue sections are first cooled from ϩ25°to ϩ4°C has a significant effect on the membrane permeability to water when these tissues are subsequently frozen in molar concentrations of either glycerol, dimethylsulfoxide or ethylene glycol. 27,28 More importantly, the subzero permeability values are lower by a factor of 10 (or even 100) from the suprazero permeability values obtained in the present study (as shown in Tables 1 to 4). Although spermatozoa with their unique morphology differ substantially in size, shape and their surface area/volume ratio from ovarian follicles, we do note that analogous large differences between permeability coefficients at suprazero versus subzero temperatures have also been found for spermatozoa of several species.…”

“…However, comparison of the permeability coefficients of ovarian follicles from the present study with recently published permeability coefficients of pieces of ovarian tissues at subzero temperatures (in the presence of extracellular ice) reveals significant differences. For example, the permeability of equine ovarian tissues at subzero temperatures ranged from 0.01 to 0.12 ϫ 10 Ϫ14 m 3 /N-sec 27 and the corresponding parameters for macaque ovarian tissues ranged from 0.026 to 0.12 ϫ 10 Ϫ14 m 3 /N-sec. 28 Interestingly, the rate at which equine and macaque ovarian tissue sections are first cooled from ϩ25°to ϩ4°C has a significant effect on the membrane permeability to water when these tissues are subsequently frozen in molar concentrations of either glycerol, dimethylsulfoxide or ethylene glycol.…”

Dual Dependence of Cryobiogical Properties of Sf21 Cell Membrane on the Temperature and the Concentration of the Cryoprotectant

“…The mean value of the inactive cell volume is 0.518 and the standard error is 0.089, n = 25. The V b of the Sf21 is similar to mammalian ovarian tissues (0.5 V 0 ) [26], [27], [28].…”

Fertility preservation through gonadal cryopreservation

“…Cat [135,215,216] Cortical tissue [135,216] Isolated follicles [215] CSF Ultra-structural analysis [216] Xenotransplantation [135] IVC of isolated follicles for 1 week [215] Normal ultra-structure [216] Development of antral follicles [135] Follicular survival [215] No Horse [217] Cortical pieces Recovery of endocrine function [138,218] and antral follicle development [219] No Dasyurids [222] Isolated follicles Vitrification IVC and viability analysis…”