Glycine and Melatonin Improve Preimplantation Development of Porcine Oocytes Vitrified at the Germinal Vesicle Stage

Abstract

Lipid-rich porcine oocytes are extremely sensitive to cryopreservation compared to other low-lipid oocytes. Vitrification has outperformed slowing freezing in oocyte cryopreservation and is expected to improve further by minimizing cellular osmotic and/or oxidative stresses. In this study, we compared the effects of loading porcine cumulus-oocyte complexes with glycine (an organic osmolyte) or glycine plus melatonin (an endogenous antioxidant) during vitrification, thawing and subsequent maturation to mitigate osmotic injuries or osmotic and oxidative damages on the developmental potential of porcine oocytes. Our data demonstrated that glycine treatment significantly increased the vitrification efficiency of porcine oocytes to levels comparable to those observed with glycine plus melatonin treatment. It was manifested as the thawed oocyte viability, oocyte nuclear maturation, contents of reactive oxygen species, translocation of cortical granules and apoptotic occurrence in mature oocytes, levels of ATP and transcripts of glycolytic genes in cumulus cells (markers of oocyte quality), oocyte fertilization and blastocyst development. However, the latter was more likely than the former to increase ATP contents and normal mitochondrial distribution in mature oocytes. Taken together, our results suggest that mitigating osmotic and oxidative stresses induced by vitrification and thawing can further enhance the developmental competency of vitrified porcine oocytes at the germinal vesicle stage.

Endocrine disorders and fertility and pregnancy: An update

“…Similarly in animal studies, the melatonin level in the follicular fluid correlated with the quality of oocytes and ovarian reserve ( 106 , 107 ). In addition, melatonin seems to be a good component of cryopreserves used in the storage of the oocytes ( 108 – 110 ). The induction of estradiol production by granular cells was also confirmed ( 106 ).…”

Application of Nanoparticles and Melatonin for Cryopreservation of Gametes and Embryos

“…In pigs, Tang et al reported that a melatonin-glycine mixture improves the development of vitrified GV oocytes via regulating osmotic stresses [ 45 ]. In 2021, Zhang et al presented that melatonin maintains the permeability of the oolemma and suppresses oxidative stress through upregulation of aquaporin-1 expression in human vitrified oocytes [ 46 ]…”

“…Melatonin (N-acetyl-5-methoxytryptamine) is a hormone secreted from vertebrate pineal gland and regulates homeostasis of reproductive tissues such as ovary and placenta [ 22 ] through receptor-mediated signaling pathways [ 23 ]. Recent studies have reported that melatonin plays a critical role in the cryopreservation of sperm [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ], oocytes [ 40 , 41 , 42 , 43 , 44 , 45 , 46 ], and embryos [ 47 , 48 , 49 , 50 , 51 ] in various species. In addition, melatonin is an antioxidant that acts as a free radical scavenger and affects G-protein-coupled receptor-related signaling transduction [ 23 , 52 ].…”

Influences of glycine supplementation during vitrification on the developmental potential of vitrified/warmed immature dromedary camel oocytes

“…Glycine is an osmolyte that was reported to protect oocyte mitochondrial homeostasis and improved blastocyst development rates following IVF in mice (Cao et al, 2016;Zander-Fox et al, 2013). It also enhanced the developmental competence of vitrified/warmed ovine and porcine oocytes (Ahmadi et al, 2019;Tang et al, 2022).…”

“…Glycine is an osmolyte that was reported to protect oocyte mitochondrial homeostasis and improved blastocyst development rates following IVF in mice (Cao et al, 2016; Zander‐Fox et al, 2013). It also enhanced the developmental competence of vitrified/warmed ovine and porcine oocytes (Ahmadi et al, 2019; Tang et al, 2022). Besides, glycine is one of the organic osmolytes which were verified to protect embryos from osmotic stress when grown under hyperosmotic circumstances (Richards et al, 2010).…”