Lipid Content of Non‐cultured and Cultured Pig Embryo

Abstract

The objectives of the study were: (i) to work out a precise and efficient method for quantitative analysis of lipid content and (ii) to quantitatively determine the lipid content in non-cultured and cultured pig embryos. The experiment was carried out on pig embryos from zygote to late blastocyst stages produced in vivo and embryos collected at the zygote stage and then cultured in vitro up to blastocyst stage. Embryos were fixed, dehydrated, embedded in epoxy resin and cut into semi-thin sections to analyse the quantity of lipids in fat droplets. Stained sections were then analysed with Cavalieri and point counting methods to evaluate the following stereological parameters of the embryo: total embryo volume - V(e), volume density of cytoplasm per unit volume of embryo - Vv(c,e), volume density of lipid droplets per unit volume of embryo cytoplasm - Vv(fat,c) and total volume of lipid droplets per whole embryo - V(fat). Values of Vv(fat,c) and V(fat) remained unchanged up to the morula stage, but decreased significantly at blastocyst and late blastocyst stages both in cultured and non-cultured embryos. Volume density of lipid droplets per unit volume of embryo cytoplasm and total volume of lipid droplets for cultured embryos showed statistically significant differences between late blastocyst and almost all other stages. Comparisons of Vv(fat,c) in embryos at the same stages of development but differing in origin of embryos (non-cultured or cultured) show that statistically significant differences exist for all analysed stages. In conclusion, differences in lipid content observed in pig embryos were dependent on the developmental stage of the embryo as well as the culture conditions (i.e. cultured and non-cultured embryos at the same stage of development).

Characterisation of the dynamic behaviour of lipid droplets in the early mouse embryo using adaptive harmonic generation microscopy

“…Elevated LD content has been associated with suboptimal embryo health and increased cryo-sensitivity in bovine embryos [38]. In porcine embryos, in vitro cultured embryos had more LD than non-cultured (presumably healthier) embryos [39]. THG can be used to quantify LD volume and number in live embryos without staining, providing objective criteria for assessing embryo quality.…”

Current progress in oocyte and embryo cryopreservation by slow freezing and vitrification

“…Others suggest that they are needed as a lipid source for cell division (Yoneda et al 2004). Lipid content depends on the stage of embryo development, significantly decreasing after the morula stage (Romek et al 2009), thus making early stages more susceptible to low temperatures. Following the observation that embryos with high intracellular lipid content are more prone to cryoinjury, at least three methods to manipulate these lipid droplets have been attempted.…”

The embryonic stress response to in vitro culture: insight from genomic analysis

“…The low cryotolerance (Sudano et al 2014) and cell degeneration (Huang et al 2010) observed in these embryos correlate with differential expression of genes involved in lipid biosynthesis and cholesterol metabolism (Van Hoeck et al 2015). Such effect could be due to any of the various factors present in serum (glucose, lipids, growth factors) (Leroy et al 2010), and some studies have shown that the lipid fraction of serum increases the triglyceride and cholesterol contents of IVC embryos (Abe et al 2002, Romek et al 2009.…”

“…Accumulating of evidence shows that IVC embryos bear the hallmarks of energetic stress in terms of nutrient utilisation (increased conversion of glucose to lactate), nutrient storage (lipid accumulation) and ATP synthesis (Spielmann et al 1984, Thompson et al 1991, Van Blerkom et al 1995, Khurana & Niemann 2000, Swain et al 2002, Romek et al 2009). This metabolic state occurs because of inadequate support in the in vitro environment.…”

“…Besides having an energetic deficiency, IVC embryos also differ from their in vivo counterparts in terms of lipid metabolism (Romek et al 2009). Lipids are an important source of energy and anabolic products required for embryo development.…”