Control of interferon-tau secretion by in vitro-derived bovine blastocysts during extended culture and outgrowth formation.

A series of experiments was conducted to examine the pattern of interferon-tau (IFN-tau) secretion by bovine blastocysts during extended culture in vitro. In the first experiment, blastocysts were cultured individually for three 48-hour periods. The day of blastocyst formation affected how much IFN-tau was produced during the first two culture periods, but not during the third period. The overall secretion of IFN-tau during the 6-day period increased significantly and well beyond what could be accounted for by the concomitant increase in cell numbers. In the second experiment, blastocysts were initially cultured in individual droplets for 48 hr, then plated into 48-well plates. Medium concentrations of IFN-tau were determined after 48 hr and again after 6 and 12 days of culture. Initial IFN-tau secretion did not affect the ability to form outgrowths or their final size, and initial differences in secretion between groups of blastocysts had disappeared by the second and third analyses. In the third experiment, blastocysts were cultured individually for 48 hr in droplets containing the medium that had been flushed through the uteri of non-pregnant sheep on days 10, 12, and 15 of the estrous cycle. Culture in the medium obtained from the Day 15 flush significantly increased the number of cells that blastocysts contained, as well as IFN-tau secretion.