Inhibition of trophoblast stem cell potential in chorionic ectoderm coincides with occlusion of the ectoplacental cavity in the mouse.
At the blastocyst stage of pre-implantation mouse development, close contact of polar trophectoderm with the inner cell mass (ICM) promotes proliferation of undifferentiated diploid trophoblast. However, ICM/polar trophectoderm intimacy is not maintained during post-implantation development, raising the question of how growth of undifferentiated trophoblast is controlled during this time. The search for the cellular basis of trophoblast proliferation in post-implantation development was addressed with an in vitro spatial and temporal analysis of fibroblast growth factor 4-dependent trophoblast stem cell potential. Two post-implantation derivatives of the polar trophectoderm - early-streak extra-embryonic ectoderm and late-streak chorionic ectoderm - were microdissected into fractions along their proximodistal axis and thoroughly dissociated for trophoblast stem cell culture. Results indicated that cells with trophoblast stem cell potential were distributed throughout the extra-embryonic/chorionic ectoderm, an observation that is probably attributable to non-coherent growth patterns exhibited by single extra-embryonic ectoderm cells at the onset of gastrulation. Furthermore, the frequency of cells with trophoblast stem cell potential increased steadily in extra-embryonic/chorionic ectoderm until the first somite pairs formed, decreasing thereafter in a manner independent of proximity to the allantois. Coincident with occlusion of the ectoplacental cavity via union between chorionic ectoderm and the ectoplacental cone, a decline in the frequency of mitotic chorionic ectoderm cells in vivo, and of trophoblast stem cell potential in vitro, was observed. These findings suggest that the ectoplacental cavity may participate in maintaining proliferation throughout the developing chorionic ectoderm and, thus, in supporting its stem cell potential. Together with previous observations, we discuss the possibility that fluid-filled cavities may play a general role in the development of tissues that border them.
Mammalian Development Laboratory, University of Oxford, Department of Zoology, South Parks Road, Oxford, OX1 3PS, UK. gary.uy@zoo.ox.ac.uk
Gary D
GD
Uy
Karen M
KM
Downs
Richard L
RL
Gardner
D000482:Allantois / Q000166:cytology; D000818:Animals; D002455:Cell Division; D002823:Chorion / Q000166:cytology* / Q000378:metabolism; D046508:Culture Techniques; D004475:Ectoderm / Q000166:cytology* / Q000378:metabolism; D005314:Embryonic and Fetal Development; D005260:Female; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D008938:Mitosis; D011247:Pregnancy; D015398:Signal Transduction; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism; D014327:Trophoblasts / Q000166:cytology* / Q000378:metabolism
C112971:fibroblast growth factor 14; D005346:Fibroblast Growth Factors