Lipid modulators during in vitro maturation of porcine oocytes
Resumo
Swine in vitro embryo production (IVP) has limitations for better outcomes in
reproductive biotechnologies. Among factors impairing IVP, high lipid content in both
oocytes and embryos, insufficient media composition and consequent reactive oxygen
species (ROS) production are the most prominent. The 1
st paper of this dissertation
contains a review regarding metabolizers included into the IVP system in order to
sustain nuclear and cytoplasmic maturation, as well as improvement of lipid droplet
(LD) consumption. The 2
nd paper reports a study where 50µM DHA was added during
the maturation period, with and without porcine follicular fluid (pFF) supplementation.
The results demonstrated that DHA without pFF impairs maturation and embryo
development. Also, there was no reduction of the lipid content in oocytes treated with
DHA, a finding that might be related to metabolic disorders in the cumulus-oocyte
complexes (COC). During maturation period, porcine oocytes prefer glucose as
substrate for energy consumption. Phenazine Ethosulfate (PES) is an electron
receptor that converts NADPH to NADP, inducing glucose utilization through the
pentose phosphate pathway (PPP), influencing lipid droplets (LD) metabolism.
Forskolin (FSK) is another chemical modulator that stimulates lipolysis through cAMP
activation, being also able to synchronize cytoplasmic and nuclear maturation of
oocytes. In the 3
rd paper, two concentrations of PES (0.5µM and 0.05µM) and one of
FSK (10 µM) were used during the entire in vitro maturation period, for two different
experiments. In Experiment 1, oocyte maturation and lipid content were evaluated; and
embryo development, embryo cell count and lipid content of blastocysts on day 7 were
evaluated in Experiment 2. The concentration of 0.5µM of PES had a negative impact
on most of the evaluated parameters, while the lowest PES dose was similar to the
negative control (NC) and FSK control in both data of Experiment 1, but also had lower
cleavage rates when compared to NC in Experiment 2. Taken together, our results
demonstrated impairment of embryo development due to possible disharmony on
oocyte maturation and metabolism disorder caused by either addition of DHA or PES.
Also, FSK did not improve maturation rates or reduced lipid content.