cAMP Modulators before In Vitro Maturation Decrease DNA Damage and Boost Developmental Potential of Sheep Oocytes

Cyclic AMP mediates ovine cumulus-oocyte gap junctional function via balancing connexin 43 expression and phosphorylation

Gap junction channels in cumulus-oocyte complexes (COCs) enable the transmission and communication of small molecular signals between adjacent cells, such as cAMP. However, the regulation of gap junction function (GJF) by cAMP and the underlying mechanisms involved are not fully clarified. This study investigated the effect of cAMP on connexin 43 (CX43) expression and GJF in ovine COCs using immunofluorescence, quantitative real-time PCR (qRT-PCR), western blotting, and GJF detection. The CX43 was only found in the cumulus cells (CCs) side of ovine COC. The intra-oocyte cAMP showed a significant increase at 30 min, while the intra-CC cAMP exhibited two peaks at 10 min and 1 h during in vitro maturation (IVM). Phosphorylated CX43 protein exhibited an immediate increase at 10 min, and CX43 protein displayed two peaks at 10 min and 1 h during IVM. The duration of pre-IVM exposure to forskolin and IBMX significantly enhanced phosphorylated and total CX43, as well as Gja1 and Creb genes, for 10 min; these effects were counteracted by Rp-cAMP. Both pre-IVM with forskolin and IBMX for 1 h and the GJF and CX43/p-CX43 ratio were elevated. The closure of gap junction channels caused by phosphorylated CX43 to prevent cAMP outflow from oocytes in early IVM of COC. Cyclic AMP upregulated phosphorylated and total CX43 via genomic and non-genomic pathways, but its functional regulation was dependent on the balance of the two proteins. This study provides a new insight into the regulatory mechanism between cAMP and GJF, which would improve IVM in animal and clinical research.

Effects of forskolin on cryopreservation and embryo development in the domestic cat

One of the approaches to improve cryotolerance in lipid-rich embryos is to modify their lipidome in vitro. This work is aimed to study the effects of forskolin exposure on the in vitro embryo development of the domestic cat and to evaluate how the change in lipid content affects the cryopreservation results. In vitro-derived embryos were cultured with 10 μM forskolin from the 2-cell stage for 24 h or 96/168 h to the morula/blastocyst stage. Some of the embryos treated with forskolin for 24 h were cryopreserved with slow freezing, the other ones were used to characterize their developmental rates and the amount of intracellular lipids. The in vitro exposure to forskolin had a positive effect on the embryo development, as more embryos developed to the morula stage in the forskolin-treated group (92.9%) compared to the controls (64.7%) after 120 h of in vitro culture (IVC). Nile Red staining revealed a reduced amount of intracellular lipids in the forskolin-treated embryos. The percentage of embryos developed to the morula stage was lower in the frozen-thawed embryos not treated with forskolin (54.5%), but not in the frozen-thawed forskolin-treated group (63.6%) as compared to non-frozen controls (80.8%). Thus, the exposure of embryos to forskolin in vitro reduced the level of intracellular lipids and affected embryo development before and after cryopreservation.

The role of forskolin as a lipolytic stimulator during in vitro oocyte maturation and the in vitro embryo production of livestock

Cryopreservation is a modern technique which assists in the preservation of genetic material from oocytes and embryos for a long time. However, elevated vulnerability to cryopreservation due to the large accumulation of intracellular lipids within oocytes or embryos avoids success of this method. These lipids remain the main crucial factor limiting survival rates of oocytes and embryos after thawing. Lipid ingathering in the oocyte cytoplasm augments lipid peroxidation (LPO) and oxidative stress increases the apoptosis process, declines the viability after thawing, declines cytoskeleton actin filament injuries, lowers the blastocyst rates and reduces cryotolerance in the early stages of embryo development. There have been several attempts to reduce the ingathering of intracellular lipids in oocytes or embryos during the cryopreservation process, in that way enhancing the competence of cryopreserved oocytes or embryos and increasing their viability. One of the most applied agents for chemical delipidation is forskolin. Forskolin exhibited a possible part in improving the oocytes cryopreservation through stimulating cyclic adenosine monophosphate (cAMP) production. The main purpose of cAMP modulation is to provide energy to sustain the mammalian oocytes´ meiotic arrest. The purpose of the existing article is to assess and offer more evidence concerning the forskolin utilization as a modulator of cAMP during the cryopreservation of oocytes and its influence on meiosis completion and the reorganization of cytoplasm, which are prerequisites for the development of oocytes in addition to the contribution to fertilization and subsequently, the development of embryos.