Protective effects of melatonin on the in vitro developmental competence of bovine oocytes

Abstract

The present study investigated the effects of melatonin on bovine oocyte maturation and subsequent embryonic development in vitro. Results showed that the nuclear and cytoplasmic maturation, characterized by first polar body extrusion, normal distribution of cortical granules and mitochondria, as well as increased mitochondrial membrane potential, were significantly improved in 10 mol/L melatonin-treated oocytes. Melatonin supplementation reduced intracellular reactive oxygen species level and enhanced glutathione production. Meanwhile, the presence of melatonin (10 mol/L) during oocyte maturation resulted in a decreased early apoptotic rate in oocytes. After in vitro fertilization, oocytes receiving melatonin supplementation exhibited a significantly higher blastocyst formation rate and yielded a markedly lower number of apoptotic cells. Mechanistic explorations showed that addition of 10 mol/L melatonin to in vitro maturation media significantly attenuated the transcript level of caspase-3, while the expressions of BCL-2, XIAP, CAT and HSP70 were significantly reinforced in the resultant embryos. Taken together, melatonin ameliorates bovine oocyte maturation potential, and the beneficial effects can affect subsequent embryonic development. The protective role of melatonin may be due to its anti-apoptotic and anti-oxidative activities.

Effects of Melatonin Administration to Pregnant Ewes under Heat-Stress Conditions, in Redox Status and Reproductive Outcome

“…A similar pattern of developmental adjustment of thermal resistance has been described in sheep in in vivo conditions, as well [52]. Furthermore, the addition of melatonin to the ovary storage medium had beneficial effects on sheep oocyte development and embryo quality by reducing the oxidative stress caused by ROS and preventing the deterioration of oocytes [53][54][55]. Two high-affinity G-protein-coupled receptors, melatonin MT1 and MT2 receptors, are expressed in sheep oocytes, cumulus cells, and granulosa cells [56], and the presence of MT1 receptors was found in sheep blastocysts, confirming the direct impact of melatonin on embryo development [53].…”

Oxidative homeostasis in oocyte competence for in vitro embryo development

“…In addition, the change in oxidative homeostasis may be more prominent in a given oocyte group, due to its initial levels of ROS and GSH, further increasing the difference in oocyte competence between groups. The significance of oxidative homeostasis has been demonstrated in studies that analyzed ROS and GSH levels with the addition of exogenous antioxidants in in vitro maturation, thereby improving the results of the in vitro produced embryos (Keshavarzi et al, ; Liang et al, ; Pang et al, ; Sovernigo et al, ). In addition, according to the results of these studies, the addition of exogenous antioxidants probably leads to optimization in oxidative homeostasis levels, similar to those found in oocytes soon after follicular removal.…”

Importance of Melatonin in Assisted Reproductive Technology and Ovarian Aging

“…Figure 3 summarizes the mechanism of melatonin that are assumed to improve oocyte maturation and quality based on reports to date. Melatonin membrane receptors (MT1, MT2) are located in oocytes and granulosa cells (cumulus cells) [58][59][60][61]; it would be of great interest to determine the intracellular signaling pathway by which melatonin promotes oocyte maturation and embryo development. While some reports have examined these intracellular processes of melatonin in oocytes [62][63][64][65], the details remain unclear.…”