Trophoblastic cell lines generated from tumour necrosis factor receptor-deficient mice reveal specific functions for the two tumour necrosis factor receptors

In mice and humans, expression of the tumour necrosis factor receptor-1 (TN F-R1) gene in placental trophoblast cells is constitutive whereas expressio n of the TNF-R2 gene is developmentally programmed. In order to study the i ndividual functions of TNF-R1 and -R2 in this lineage, cell lines were gene rated from placental explants of homozygous matings of gestation day 10 out bred mice (Swiss-Webster), TNF-R1-deficient (TNF-R1 (- / -)) and TNF-R2 (- / -) transgenic mice as well as the background strain for the TNF-R2 (- / - ) mice (WT, C57BL/6 x 129). All of the cells exhibited trophoblast markers; they contained cytokeratin intermediate filaments, expressed alkaline phos phatase activity and displayed transferrin receptors, but were negative for vimentin filaments and the macrophage marker, F4/80. Analysis of DNA by po lymerase chain reaction demonstrated the expected TNF-R genotype in each li ne. In experiments testing the effects of recombinant mouse TNF-alpha (rmTN F-alpha) on viability and proliferation of the cell lines, rmTNF-alpha mode stly but dose-dependently inhibited the growth of WT and TNF-R2 (- / -) cel ls while having no effect on TNF-R1 (- / -) cells. Actinomycin D-treated WT and, to a lesser extent, TNF-R2 (- / -) cells, were more sensitive to grow th inhibition than untreated cells whereas TNF-R1 (- / -) cell responses re mained unchanged. These data indicated that rmTNF-alpha inhibits growth of trophoblastic cells through TNF-R1 and that newly synthesized protein(s) pr ovide partial protection against toxicity. In contrast to the receptor spec ies-specific effects on cell growth exerted by rmTNF-alpha, both TNF-R medi ated inhibition of alkaline phosphatase activity. Collectively, the observa tions support the postulate that receptor expression is the key factor whic h determines the nature and extent of TNF-alpha effects on trophoblast cell growth and function. (C) 1999 W. B. Saunders Company Ltd.