Cytotrophoblast differentiation in the first trimester of pregnancy: evidence for separate progenitors of extravillous trophoblasts and syncytiotrophoblast.
It is commonly accepted that a single pool of villous cytotrophoblasts are precursors of both syncytiotrophoblast and extravillous trophoblasts during the first trimester. Here we present evidence that these two trophoblast subpopulations arise from separate progenitors that have different survival characteristics when studied in villous explant cultures. Dual staining with chloromethylfluorescin diacetate and ethidium bromide revealed degeneration of the syncytiotrophoblast by non-apoptotic mechanisms within 4 h of culture. The syncytiotrophoblast had regenerated within 48 h but at this point the vast majority of the cytotrophoblast and cells of the mesenchymal core were dead. Despite this extensive cytotrophoblast death, explants are able to produce extravillous trophoblast outgrowth for up to 3 weeks in culture. We believe that the villous cytotrophoblasts in the tips of anchoring villi are resistant to the factors that cause the death of the majority of villous cytotrophoblasts in culture. We speculate that as early as 8 weeks of gestation there are two separate villous cytotrophoblast populations, one committed to differentiate into syncytiotrophoblast and the second committed to the extravillous differentiation pathway.
Department of Obstetrics and Gynecology, Room 3241 C/-, Department of Surgery, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92109, Auckland, New Zealand. j.james@auckland.ac.nz
Joanna L
JL
James
Peter R
PR
Stone
Lawrence W
LW
Chamley
D017209:Apoptosis; D016923:Cell Death; D002454:Cell Differentiation; D004396:Coloring Agents; D005260:Female; D005562:Formazans; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D018613:Microscopy, Confocal; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D013778:Tetrazolium Salts; D046509:Tissue Culture Techniques; D014327:Trophoblasts / Q000166:cytology*
D004396:Coloring Agents; D005562:Formazans; D013778:Tetrazolium Salts; C079782:MTT formazan