Membrane-permeable trehalose improves the freezing ability and developmental competence of in-vitro matured feline oocytes

Oocytes are highly sensitive to cryopreservation, which frequently results in an irreversible loss of developmental competence. We examined the effect of membrane-permeable trehalose on the freezing ability of feline oocytes matured in vitro. In Experiment 1, intracellular trehalose (trehalose hexaacetate; Tre-(OAc)(6)) was synthesized from trehalose precursor and subjected to spectroscopic characterization. The membrane permeability of the Tre-(OAc)(6) was investigated by incubating oocytes with different concentrations of Tre-(OAc)(6) (3, 15, and 30 mM). Optimum concentration and the toxicity of Tre-(OAc)(6) were assessed in Experiment 2. The effects of Tre-(OAc)(6) on freezing ability in terms of apoptotic gene expression and developmental competence of in-vitro matured oocytes were examined in Experiments 3 and 4, respectively. The Tre-(OAc)(6) permeated into the ooplasm of cat oocytes in a dose-and time dependent manner. The highest concentration of intracellular trehalose was detected when the oocytes were incubated for 24 h with 30 mM Tre-(OAc)(6). For the toxicity test, incubation of oocytes with 3 mM Tre-(OAc)(6) for 24 h did not affect maturation rate and embryo development. However, high doses of Tre-(OAc)(6) (15 and 30 mM) significantly reduced maturation and fertilization rates (p < 0.05). In addition, frozen-thawed oocytes treated with 3 mM Tre-(OAc)(6) significantly upregulated anti-apoptotic (BCL-2) gene expression compared with the control (0 mM) and other Tre-(OAc)(6) concentrations (15 and 30 mM). Oocyte maturation in the presence of 3 mM Tre-(OAc)(6) prior to cryopreservation significantly improved oocyte developmental competence in terms of cleavage and blastocyst rates when compared with the control group (p < 0.05). Our results lead us to infer that increasing the levels of intracellular trehalose by Tre-(OAc)6 during oocyte maturation improves the freezing ability of feline oocytes, albeit at specific concentrations.(c) 2022 Elsevier Inc. All rights reserved.