Would L-carnitine improve the survival and viability of vitrified/warmed in vitro bovine blastocysts?

Abstract

The experiment was conducted to verify the effects of delipidation using L‑carnitine on the development and survival of in vitro‑produced bovine embryos, cryopreserved by vitrification, using the evaluation of the intracytoplasmic content of lipids, cellular apoptosis, mitochondrial potential, the rates of re‑expansion and hatching post‑warming. The embryos were cultured without the addition of L‑carnitine (Control), in the presence of L‑carnitine (0.6 mg/mL) added to the culture medium of D1 to D7 (L‑Ivc), during the culture before vitrification and post‑warming re‑culture (L‑IvcR) and during in vitro maturation, in vitro culture before vitrification and post‑warming re‑culture (L‑ IvmIvcR). The supplementation with L‑carnitine did not change the cleavage rate in D3 (p ˃0.05) but increased the production of blastocysts in D7 by 20.7% and the proportion of grade I embryos by 30.1% in LIvc (p<0.05), as well as the re‑expansion rate (2‑hour) (p<0.05), but the hatching rates and the number of degenerate structures at the 24 and 48‑hour post‑warming did not differ between treatments (p˃0.05). The treatment with L‑carnitine was effective in reducing cell apoptosis, intracytoplasmic content of lipids, and mitochondrial potential of blastocysts (p<0.001). In conclusion, media supplementation with 0.6 mg/mL of L‑carnitine during in vitro embryo production improved vitrified/warmed bovine blastocysts' survival and viability, reducing cell apoptosis and intracellular lipids' amount and positively impacting mitochondrial activity potential. Under the presented conditions, this supplementation can be used only in the culture medium since no additional benefit was verified by adding this L‑carnitine concentration during oocyte maturation, blastocyst culture, or post‑warming culture.