ROLE OF PLATELET-DERIVED GROWTH-FACTOR IN DEVELOPMENT OF INVITRO MATURED AND INVITRO FERTILIZED BOVINE EMBRYOS

This experiment was designed to determine whether the stimulatory effe cts of bovine oviductal epithelial cells (BOEC) on development of earl y bovine embryos are due to platelet-derived growth factor (PDGF). Fou r hundred and twenty five 8-cell bovine embryos derived from in vitro maturation and in vitro fertilization procedures were equally and rand omly allotted to one of the following culture treatment groups: contro l medium alone (Menezo's B2 medium; MB2), MB2 with 1 ng PDGF ml-1 (PDG F), 1 ng PDGF ml-1 and 10 mug anti-PDGF antibody ml-1 (PDGF + Ab), BOE C or BOEC and 10 mug anti-PDGF antibody ml-1 (BOEC + Ab). All embryos were cultured in 100 mul of serum-free MB2 medium supplemented with 2 mg fatty-acid-free bovine serum albumin ml-1. Embryos for all treatmen t groups were incubated at 39-degrees-C and 5% CO2 in humidified air i n groups of five embryos per well in 96-well culture plates until 7 da ys after in vitro insemination. A higher proportion of embryos develop ed to > 8-cell and to the morula stage following culture with PDGF, BO EC or BOEC + Ab than with MB2 alone. Incubation of PDGF and BOEC-treat ed embryos with anti-PDGF reduced development to the morula and blasto cyst stages. However, anti-PDGF did not completely inhibit blastocyst development when added to BOEC. In addition, embryos incubated with BO EC and anti-PDGF contained a reduced number of inner cell mass cells c ompared with embryos incubated with BOEC alone. These results indicate that PDGF provides a developmental stimulus similar to BOEC for bovin e embryos at the fourth cell cycle. The addition of PDGF antibodies ap pears to reduce early embryo development by inhibiting PDGF action. Ho wever, BOEC may also produce factors other than PDGF that are benefici al to early bovine embryo development during in vitro culture.