Table 1.
Trophoblast cell types.
| Cell type | Speciesa | Placentation site location | Principal function(s) |
|---|---|---|---|
| Trophectoderm | Mouse, rat, human | Outer cellular layer of blastocyst | Embryo implantation; inner cell mass/epiblast protection; source of trophoblast stem and progenitor cells |
| Trophoblast stem progenitor cells | Mouse, rat | Prominently located in extraembryonic ectoderm; ectoplacental cone | Seed differentiated trophoblast lineages |
| Cytotrophoblast | Human | Beneath syncytiotrophoblast layer (villous compartment); Base of extravillous trophoblast column (extravillous compartment) | Trophoblast stem and progenitor cell population; seed differentiated trophoblast lineages; also, postmitotic component of villous compartment |
| Primary syncytium | Human | Multinucleated trophoblast at the embryo implantation site of early pregnancy | Invasion/facilitating embryo interstitial implantation into the uterine decidua |
| Trophoblast giant cell | Mouse, rat | Junctional zone: uterine-placental interface (primary), labyrinth zone (secondary) | Endocrine activity: steroid and peptide hormonogenesis |
| Glycogen trophoblast cell | Mouse, rat | Junctional zone (transient) | Energy reserve |
| Spongiotrophoblast cell | Mouse, rat | Junctional zone | Endocrine activity: peptide hormonogenesis |
| Endovascular invasive trophoblast cell | Mouse, rat, human | Intrauterine: intravascular; extravillous compartment (human) | Uterine spiral artery restructuring |
| Interstitial invasive trophoblast cell | Mouse, rat, human | Intrauterine: extravascular; extravillous compartment (human) | Placental anchor; uterine stroma remodeling |
| Syncytiotrophoblast | Mouse, rat, human | Labyrinth zone (mouse, rat); villous compartment (human) | Barrier/transport (mouse, rat, human); endocrine activity: steroid and peptide hormonogenesis (human) |
aTrophoblast cell types found in mouse, rat, and human.