Tumor necrosis factor or decreases the viability of mouse blastocysts in vitro and in vivo

Mouse blastocysts were exposed for 24 h to various concentrations of recomb inant mouse tumor necrosis factor alpha (TNF alpha) and observed for their capacity to implant in vitro on a fibronectin-coated substrate or to develo p in vivo after their transfer into surrogate females. Compared with findin gs in control blastocysts, exposure to TNF alpha resulted in a significant reduction in the average number of cells in the inner cell mass (ICM) linea ge. This effect was associated with a significant increase in the frequency of cells identified as engaged in apoptosis by means of the terminal deoxy nucleotidyl transferase-mediated dUTP nick end-labeling technique. No diffe rence was found in the incidence of nuclear fragmentation between control a nd TNF alpha-exposed blastocysts. When TNF alpha-pretreated blastocysts wer e allowed to implant in vitro, significantly fewer embryos were able to mai ntain a structured ICM cluster at the center of the trophectoderm outgrowth . Although no difference was found in the average surface area of the outgr owths, implants derived from TNF alpha-treated blastocysts contained signif icantly fewer nuclei than implants from control embryos. After transfer int o recipient mice, TNF alpha-pretreated blastocysts implanted at about the s ame rate as control embryos, but a significantly higher rate of resorption was found among fetuses after exposure to the cytokine. In addition, the we ight of the surviving fetuses was significantly lower than for control fetu ses. These data indicate that the impact of TNF alpha on blastocysts is spe cifically aimed at the ICM lineage and that TNF alpha decreases the ability of embryos to differentiate into fetuses after implantation.