Does serum cause lipid-droplet accumulation in bovine embryos produced in vitro, during developmental days 1 to 4?

Abstract

SummaryPurpose Serum supplementation has shown to have beneficial effects on in vitro bovine embryo development. However, it is often assumed that serum supplementation may produce mitochondrial damage and this damage would generate lipid accumulation, a major obstacle for cryopreservation. The aim of the present study is to investigate the previous assumptions in early embryonic stages. Methods We considered in vitro produced bovine embryos from day 1 to 4 of development, which were grown in presence of serum from days 1, 2 or 3 or in absence of it. Electron transmission micrographs allowed us to quantify the area occupied by lipid droplets and by the different mitochondrial types to evaluate serum effect. Using confocal microscopy we analyzed mitochondrial activity and location. Results We found no evidence of lipid droplets accumulation or mitochondrial degeneration or reduction of mitochondrial area in serum supplemented media. Further, our results suggest that events of mitochondrial proliferation are taking place even in serum supplemented media.Conclusions Serum does not produce lipid accumulation or mitochondrial damage in bovine embryos from 2 to 16 cells. When serum was added to embryo culture medium on day 3 of development, there were ultrastructural signs of a beneficial effect for embryo development. The lack of serum until day 3 may also avoid the unnecessary exposure to potentially inhibitory factors present on it.

Ultrastructural Characterization of Fresh and VitrifiedIn Vitro-andIn Vivo-Produced Sheep Embryos

“…Likewise Crocco et al. () reported a negative association between the area covered by lipid droplets and hooded mitochondria in cattle embryos. Lipid droplets are the main storage of triacylglycerols in the embryo (Lapa et al., ; Prates et al., ) and are present in high content in in vitro ‐produced BL.…”

“…Moreover, the higher degree of cell damage with complete cell lysis, disruption of cytoplasmic and nuclear membranes can also be associated with severe mitochondrial damage (Cocero et al., ; Bettencourt et al., ) and impaired lipid metabolism (Abe et al., ; Prates et al., ). This negative association may indicate that the increase in mitochondrial area enhances the ability to perform embryonic β ‐oxidation of fatty acids and that impaired mitochondria and lipid accumulation are detrimental for embryo development (Crosier et al., ; Crocco et al., ). In fact, mitochondria metabolize fatty acids via the β ‐oxidation pathway to generate cellular ATP essential for embryonic development (Dunning et al., ).…”

Substituição Parcial Do Soro Fetal Bovino Durante Cultivo in Vitro Reduz a Concentração De Fosfolipídios Em Embriões Bovinos Produzidos in Vitro

“…The comparison of our results with literature data, shows that partial protein replacement seems to be more adequate than full substitution, since full FBS replacement by BSA during oocyte maturation and embryo culture decreased embryo production (Sena-Netto et al, 2020). One major challenge in IVP is to develop an appropriate growth medium, which mimics the essential components to the proper development of the embryo, reducing cell stress, loss of viability and allowing a technical improvement (Gómez et al, 2008;Cagnone and Sirard, 2014).…”

“…Assisted reproductive technologies (ARTs) are frequently used in domestic animals and a high number of bovine embryos are produced annually, but these techniques still reduce the quality and embryo rate production (Cagnone and Sirard, 2014). The development of a zygote until blastocyst stage during in vitro culture (IVC) is considered the most critical period of in vitro production (IVP) of embryos (Lonergan et al, 2003).…”

Beyond energy provider: multifunction of lipid droplets in embryonic development

“…Feeding fish oil to broiler females during gestation can reduce fat deposition in the offspring and reduce the potential risk of obesity in the offspring [ 60 ]. The effect of adding a synthetic serum to cultured embryos was similar to that of adding fetal calf serum [ 61 ], and the serum did not cause lipid accumulation or organelle damage to bovine embryonic cells [ 62 ], reducing the concentration of fetal bovine serum to 5% for culturing in vitro embryonic cells is an appropriate concentration [ 63 ]. Supplementation with all-trans retinoic acid [ 64 ], L-carnitine [ 65 ], melatonin [ 66 ], and dehydroepiandrosterone [ 67 ] in serum can improve in vitro embryo culturing, which provides a method for the livestock industry including other fields that require embryo culturing in vitro, and hopefully, more serum additives will enhance embryo In vitro culture viability.…”