Supplementation of fetal bovine serum alters histone modification H3R26me2 during preimplantation development of in vitro produced bovine embryos

Abstract

In vitro production (IVP) of bovine embryos is not only of great economic importance to the cattle industry, but is also an important model for studying embryo development. The aim of this study was to evaluate the histone modification, H3R26me2 during pre-implantation development of IVP bovine embryos cultured with or without serum supplementation and how these in vitro treatments compared to in vivo embryos at the morula stage. After in vitro maturation and fertilization, bovine embryos were cultured with either 0 or 2.5% fetal bovine serum (FBS). Development was evaluated and embryos were collected and fixed at different stages during development (2-, 4-, 8-, 16-cell, morula and blastocyst). Fixed embryos were then used for immunofluorescence utilizing an antibody for H3R26me2. Images of stained embryos were analyzed as a percentage of total DNA. Embryos cultured with 2.5% FBS developed to blastocysts at a greater rate than 0%FBS groups (34.85±5.43% vs. 23.38±2.93%; P<0.05). Levels of H3R26me2 changed for both groups over development. In the 0%FBS group, the greatest amount of H3R26me2 staining was at the 4-cell (P<0.05), 16-cell (P<0.05) and morula (P<0.05) stages. In the 2.5%FBS group, only 4-cell stage embryos were significantly higher than all other stages (P<0.01). Morula stage in vivo embryos had similar levels as the 0%FBS group, and both were significantly higher than the 2.5%FBS group. These results suggest that the histone modification H3R26me2 is regulated during development of pre-implantation bovine embryos, and that culture conditions greatly alter this regulation.

Supplementation of fetal bovine serum increased the quality of in vitro fertilized porcine embryo

“…The percentages of BLs development and the total cell number per BL were significantly increased in the medium supplemented with FBS. Similar results were found in IFV porcine embryo development where 10% FBS was added in the chemically defined medium [ 19 ], and also 2.5% FBS was used for IVF bovine embryo production [ 20 ]. However, it was found that 5% FBS has been advantageous during the pre-cleavage stage, and 10%–20% FBS has been advantageous during the post-cleavage stage of the bovine embryos and also overcomes the deleterious effects of serum on early developing embryos by exploiting embryotrophic effects during later stage [ 21 ].…”

“…Another study on bovine embryo culture indicated that adding FBS in the culture medium promoted development to the morula and BL stage [ 20 ]. Mostly, FBS acts as a protein source in the culture medium.…”

“…This would be consistent with the idea that superior quality embryos contain higher mRNA levels from the anti-apoptotic gene and conversely lower levels of the pro-apoptotic transcriptome. However, FBS had some detrimental effects when used in porcine parthenote, and in that case, the total numbers of cells per BL were significantly reduced and apoptotic cells were significantly increased [ 20 ]. In fact, increased expression of the anti-apoptotic gene BCL-2 in embryos determined the presence of embryos with good morphological quality in IVC media [ 32 ].…”