COCULTURE OF INVITRO FERTILIZED BOVINE EMBRYOS WITH DIFFERENT CELL MONOLAYERS

The effects of different cell monolayers on in vitro development of early bovine embryos derived from in vitro maturation and fertilization were examined in this study. Early embryos (four to eight cells) were randomly allocated to bovine granulosa cell (GC), oviductal cell (OC), or uterine cell (UC) monolayers in Exp. 1 and to GC, skin cell (SC; from 10-d-old chicken embryos), testicular cell (TC; from 10-d-old mouse), and liver cell (LC; from 10-d-old chicken embryos) monolayers in Exp. 2, and cultured for 6 d at 38.6-degrees-C in a humidified atmosphere of 5% CO2 in air. The culture medium was 12.5 mM HEPES TCM 199 supplemented with 1% calf serum and 1 mM sodium pyruvate. In Exp. 1, the percentage of four-to eight-cell embryos that developed to blastocysts on GC, OC, and UC monolayers was 26.9 (28/104), 37.5 (39/104), and 39.2 (40/102), respectively. In Exp. 2, the percentage of four- to eight-cell embryos that developed to blastocysts on GC, SC, TC, and LC monolayers was 53.3 (40/75), 42.9 (33/77), 49.3 (37/75), and 44.3 (35/79), respectively. There were no significant differences in development among groups in either experiment. Embryos co-cultured with bovine OC developed faster, and those co-cultured with mouse TC developed slower, because the percentage (100 x number of blastocysts obtained by d 5/number of blastocysts obtained by d 6) of blastocysts developing by d 5 of culture on GC, OC, and UC monolayers was 50.0 (14/28), 82.0 (32/39), and 67.5 (27/40), respectively, and those on GC, SC, TC, and LC monolayers were 80.0 (32/40), 81.8 (27/33), 48.6 (18/37), and 74.3 (26//35), respectively. The results of this study suggest that the embryotrophic or embryo-regulating factors may not be strictly oviduct- and species-specific.