Fatty acids and L-carnitine supplementation in vitrification media improves oocyte mitochondrial function and inner...

Fatty acid-supplemented warming solutions have been shown to improve blastocyst development and pregnancy outcomes after single vitrified-warmed cleavage stage embryo transfers. However, the effects of fatty acids, phospholipids, and L-carnitine on oocyte mitochondrial function and blastocyst development remain unexplored. This study aimed to evaluate whether supplementing both vitrification and warming solutions with these compounds enhance oocyte mitochondrial function and embryo development.

Preclinical study conducted with a C57Bl/6 J mouse strain. The study included five experimental groups. The control group comprised fresh oocytes not subjected to vitrification. The vitrification groups consisted of oocytes vitrified in Tvitri-4 medium supplemented with L-carnitine (T4/LC), L-carnitine and fatty acids (T4/FA), or L-carnitine, fatty acids, and phosphatidylcholine (T4/PC). Total cell number in the trophectoderm and inner cell mass (ICM) was analyzed by differentially labeling the nuclei with polynucleotide-specific fluorochromes. Oocyte mitochondrial activity was assessed by mitochondrial membrane potential (ΔΨm), intracellular oxidant levels, and oxidative metabolism. ΔΨm and the levels of oxidant species were evaluated using JC-1 and carboxy-H2DCFDA, respectively, while redox state was measured by the FAD/NAD(P)H autofluorescence ratio.

The ICM cell number did not differ between fresh and oocytes vitrified and warmed with L-carnitine and lipids (Tvitri-4/fatty acids and Tvitri-4/phosphatidylcholine) (p > 0.05). Additionally, oleic and linoleic acids with L-carnitine preserved mitochondrial membrane potential and reduced oxidative stress by lowering oxidant levels.

Adding lipids to the vitrification and warming solutions can modulate mitochondrial membrane potential and the production of oxidant species in mouse oocytes.