Effect of glycosaminoglycans on the preimplantation development of embryos derived from in vitro fertilization and somatic cell nuclear transfer

Abstract

The purpose of this study was to evaluate the effect of glycosaminoglycans (GAGs) added to the culture medium on the developmental competence of bovine embryos derived from in vitro fertilization (IVF) and from somatic cell nuclear transfer (SCNT). In vitro-matured oocytes were either inseminated with 1 &times; 10<emph type="7">6 spermatozoa mL<emph type="7">-1 or enucleated and reconstructed with bovine adult ear fibroblasts by SCNT. The embryos were then cultured in modified synthetic oviduct fluid (mSOF) containing 8 mg mL<emph type="7">-1 bovine serum albumin (BSA) (control mSOF) or control mSOF supplemented with various GAGs (hyaluronic acid, heparin or chondroitin sulfate) in a dose-dependent manner (0.1, 0.5 or 1.0 mg mL<emph type="7">-1). Developmental competence was evaluated by monitoring the numbers of 2-cell embryos, 8-16-cell embryos and blastocysts. The mean cell number of flattened blastocysts stained with 5 &mu;<emph type="6">M bisbenzimide on Day 8 was counted. The percentage of blastocyst formation (IVF and SCNT embryos) from cleaved embryos was significantly higher (P &lt; 0.05) in control mSOF supplemented with 0.5 mg mL<emph type="7">-1 hyaluronic acid (45% and 47%), heparin (40% and 47%) or chondroitin sulfate (38% and 44%) compared with control mSOF (30-31% and 30-33%). When compared with the efficacy of 0.5 mg mL<emph type="7">-1 GAGs, no significant differences were observed in the developmental competence of both IVF and SCNT embryos. Supplementing control mSOF with 0.5 mg mL<emph type="7">-1 GAGs had no effect on the cell number of IVF embryos. In contrast, supplementing 0.5 mg mL<emph type="7">-1 of hyaluronic acid, heparin or chondroitin sulfate to control mSOF significantly (P &lt; 0.05) increased the numbers of total cells (93-98 v. 88 cells) and trophectoderm (TE) cells (64-66 v. 55 cells), and decreased the inner cell mass (ICM) to TE cell ratio (48.2-49.8 v. 61.3) in SCNT blastocysts compared with embryos in control mSOF. In conclusion, supplementation of culture media with GAGs may improve the development of bovine IVM-IVF and SCNT embryos to the blastocyst stage. The GAGs increased the quality of blastocysts by increasing total cell numbers in the SCNT embryos.