Expression of Tumor Necrosis Factor-alpha (TNF Alpha) Receptors and Selective Effect of TNF Alpha on the Inner Cell Mass in Mouse Blastocysts

The presence of tumor necrosis factor-alpha (TNF alpha) receptors was demonstrated at the cell surface of mouse blastocysts by indirect immunofluorescence. Amplification of total cDNA from these embryos indicated that only the p60 form of the TNF alpha receptor was expressed. Amplification of the p80 form remained negative. Blastocysts were cultured with 0.5, 5.0, or 50 ng/ml TNF alpha and examined for their morphology and cell proliferation rate. Doses of 5.0 and 50 ng/ml delayed the morphological development after 24 h, but this effect was no longer detected after 48 h. Overall cell proliferation was decreased by 15% with 50 ng/ml TNF alpha after 24 h and with all three concentrations after 48 h. Differential staining of the two embryonic cell lineages revealed that the reduction in cell number was at the expense of the inner cell mass, the cell group responsible for forming the fetal layers after implantation. This inhibition was not mediated by cytotoxicity, as the proportion of dead ICM cells remained low in the presence of TNF alpha. Our data indicate that the expression of TNF alpha receptors is developmentally regulated before implantation, and that preimplantation embryos are responsive to TNF alpha.