141 BENEFICIAL EFFECT OF ETHYLENEDIAMINETETRAACETIC ACID COMBINED WITH HEMOGLOBIN ON PRE-IMPLANTATION DEVELOPMENT OF PORCINE IN VITRO PRODUCED EMBRYOS

Abstract

Developing a porcine embryo culture system is important for increasing the rates of implantation and pregnancy of somatic cell nuclear transfer (SCNT) embryos. Ethylenediaminetetraacetic acid (EDTA) was shown to inhibit glycolytic activity of cleavage stage embryos, thereby preventing the premature stimulation of glycolysis and enhancing development. However, EDTA should not be used for later-stage embryos as the inhibition of glycolysis reduces energy production at the blastocyst stage and significantly inhibits inner cell mass development. On the other hand, addition of a nitric oxide (NO) scavenger, hemoglobin (Hb), to the culture medium is known to promote embryo development to the blastocyst stage. This study was conducted to evaluate the beneficial effect of EDTA combined with Hb on pre-implantation development of porcine embryos in vitro. Porcine embryos produced by in vitro maturation and fertilization were cultured for 6 days in North Carolina State University (NCSU)-23 medium supplemented with EDTA or/and Hb. All data were subjected to one-way ANOVA and protected least significant difference (LSD) test using the general linear models (GLM) procedure of the statistical analysis system (SAS Institute, Inc., Cary, NC, USA) program to determine differences among experimental groups. Statistical significance was determined when the P value was less than 0.05. In Exp. 1, culturing porcine zygotes with 100 mM EDTA (n = 537) significantly increased cleavage rates (85.3%) at 48 h post-insemination compared to supplementing with 0, 1, or 10 mM EDTA (78.9, 79.7, or 78.2%, respectively). However, EDTA at these concentrations did not promote blastocyst formation compared to the control. In addition, no difference was observed in total cell numbers in blastocysts among the experimental groups (41.8, 42.6, 45.8, 44.5, respectively). In Exp. 2, in vitro-fertilized oocytes were cultured with 0, 1, or 10 mg/mL Hb. Culturing with Hb did not promote porcine embryo development, but significantly increased the total cell number of blastocysts obtained from 1 mg/mL Hb supplementation (n = 566) compared to that of the control (56.8 vs. 41.6). In Exp. 3, culturing embryos (n = 548) with 100 mM EDTA + 1 mg/mL Hb significantly improved rates of cleavage (84.0% vs. 75.2%) and blastocyst formation (19.2% vs. 12.7%), and the total number of cells in blastocysts compared to those of the control (58.4 vs. 42.3). In conclusion, our results demonstrated that EDTA or Hb have different roles in supporting in vitro pre-implantation development of porcine embryos; EDTA mainly stimulated early cleavage up to the 2- to 4-cell stage, and Hb promoted the total cell number of blastocysts. However, combined supplementation with these two chemicals improved cleavage, blastocyst formation, and total cell number in blastocysts. This study was supported by a grant from Korea Ministry of Science and Technology (Biodiscovery).