Manipulation of autophagy regulates mitochondrial homeostasis and early embryo development of cryopreserved porcine oocytes

Abstract

Porcine oocytes experience severe mitochondrial cryoinjury after cryopreservation, posing challenge for post-warming survival and subsequent in vitro fertilization. Autophagy was involved in cellular self-renewal in cryopreserved porcine oocytes in response of stress. In this study, autophagy was manipulated in vitrified-warmed porcine oocytes by rapamycin (RAPA) or 3-methyladenine (3-MA) to assess the feasibility of autophagy modifications in redressing post-warming mitochondrial dysfunction and fertilizability. As the results, RAPA-induced autophagy redressed mitochondrial membrane potential (1.44 ± 0.06 vs 0.81 ± 0.07), inhibited oxidative stress (0.91 ± 0.11 vs 1.46 ± 0.07) and early apoptosis rate (23.74 ± 3.21 % vs 46.78 ± 4.45 %) in vitrified-warmed oocytes, promoted the viability (77.73 ± 4.24 % vs 58.87 ± 4.05 %), the cleavage rate (56.90 ± 2.97 % vs 41.10 ± 3.71 %) following parthenogenetic activation (PA) and the blastocyst rate (10.93 ± 0.82 % vs 2.63 ± 1.56 %) following in vitro fertilization (IVF) of vitrified-warmed oocytes. In contrast, inhibition of autophagy by 3-MA exacerbated mitochondrial dysfunction, oxidative stress, and early apoptosis, leading to the loss of oocyte viability, parthenogenetic potential, and IVF capacity, thus losing its practical applicability. This study regarded the manipulation of autophagy as an applicational strategy to maintain post-warming mitochondrial homeostasis and to enhance the IVF embryo outcome of cryopreserved porcine oocyte.