Role of platelet-derived growth factor in development of in vitro matured and in vitro fertilized bovine embryos

Abstract

This experiment was designed to determine whether the stimulatory effects of bovine oviductal epithelial cells (BOEC) on development of early bovine embryos are due to platelet-derived growth factor (PDGF). Four hundred and twenty five 8-cell bovine embryos derived from in vitro maturation and in vitro fertilization procedures were equally and randomly allotted to one of the following culture treatment groups: control medium alone (Menezo's B2 medium; MB2), MB2 with 1 ng PDGF ml-1 (PDGF), 1 ng PDGF ml-1 and 10 μg anti-PDGF antibody ml-1 (PDGF + Ab), BOEC or BOEC and 10 μg anti-PDGF antibody ml-1 (BOEC + Ab). All embryos were cultured in 100 μl of serum-free MB2 medium supplemented with 2 mg fatty-acid-free bovine serum albumin ml-1. Embryos for all treatment groups were incubated at 39°C and 5% CO2 in humidified air in groups of five embryos per well in 96-well culture plates until 7 days after in vitro insemination. A higher proportion of embryos developed to > 8-cell and to the morula stage following culture with PDGF, BOEC or BOEC + Ab than with MB2 alone. Incubation of PDGF and BOEC-treated embryos with anti-PDGF reduced development to the morula and blastocyst stages. However, anti-PDGF did not completely inhibit blastocyst development when added to BOEC. In addition, embryos incubated with BOEC and anti-PDGF contained a reduced number of inner cell mass cells compared with embryos incubated with BOEC alone. These results indicate that PDGF provides a developmental stimulus similar to BOEC for bovine embryos at the fourth cell cycle. The addition of PDGF antibodies appears to reduce early embryo development by inhibiting PDGF action. However, BOEC may also produce factors other than PDGF that are beneficial to early bovine embryo development during in vitro culture.