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Background: The placenta is a temporary organ that develops throughout pregnancy, connecting a developing fetus to the maternal uterine wall. The placenta’s structure is species specific and complex, resulting in recent advancements with in vitro models to help study this dynamic organ. The main cell type composing the placenta, trophoblast cells, serve several roles and have been incorporated within biomaterials and devices to recapitulate the placental microenvironment. Summary: This review highlights in vitro 2D, 3D, and on-a-chip models of two placental interfaces: the interface between the endometrium and extravillous trophoblast cells and the interface between the chorionic villi and intervillous space. First, an overview of placental cell types and in vitro model types used in the discussed studies is provided. Next, models of invasive trophoblasts cells at the endometrium where the placenta is anchored and the spiral arteries are remodeled are discussed. Next, the review highlights models of the chorionic villi and intervillous space, an interface where cytotrophoblast cells fuse into syncytiotrophoblasts. Finally, we discuss key takeaways and future directions in creating representative placental models.Key Messages: The combination of biomaterial and engineering approaches has led to the development of physiologically relevant models, allowing placental trophoblast functions to be investigated with more clarity. Each cell type (e.g. trophoblast cell line vs. stem cells vs. primary placental cells) and biomaterial system (e.g. organoid vs. on-a-chip) that is selected for a given model has a unique combination of advantages and limitations, which are detailed within this review. Overall, the placental models discussed enable trophoblast cell behavior to be studied in vitro with the inclusion of extracellular matrix materials, growth factors, and other environmental cues. While one model alone does not fully recapitulate every function of the placenta, individual models are tailored to inform on specific placental trophoblast behaviors.
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Cell wall polymers in the Phaeoceros placenta reflect developmental and functional differences across generations
The placenta of hornworts is unique among bryophytes in the restriction of transfer cells that are characterized by elaborate wall labyrinths to the gametophyte generation. During development, cells around the periphery of the sporophyte foot elongate, forming smooth-walled haustorial cells that interdigitate with gametophyte cells. Using immunogold labeling with 22 antibodies to diverse cell wall polymers, we examined compositional differences in the developmentally and morphologically distinct cell walls of gametophyte transfer cells and sporophyte haustorial cells in the placenta of Phaeoceros. As detected by Calcofluor White fluorescence, cellulose forms the cell wall scaffolding in cells on both sides of the placenta. Homogalacturonan (HG) and rhamnogalacturonan I (RG-I) pectins are abundant in both cell types, and haustorial cells are further enriched in methyl-esterified HGs. The abundance of pectins in placental cell walls is consistent with the postulated roles of these polymers in cell wall porosity and in maintaining an acidic apoplastic pH favorable to solute transport. Xyloglucan hemicellulose, but not mannans or glucuronoxylans, are present in cell walls at the interface between the two generations with a lower density in gametophytic wall ingrowths. Arabinogalactan proteins (AGPs) are diverse along the plasmalemma of placental cells and are absent in surrounding cells in both generations. AGPs in placental cell walls may play a role in calcium binding and release associated with signal transduction as has been speculated for these glycoproteins in other plants. Callose is restricted to thin areas in cell walls of gametophyte transfer cells. In contrast to studies of transfer cells in other systems, no reaction to the JIM12 antibody against extensin was observed in Phaeoceros.
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- Award ID(s):
- 1758497
- PAR ID:
- 10285988
- Date Published:
- Journal Name:
- Bryophyte Diversity and Evolution
- Volume:
- 43
- Issue:
- 1
- ISSN:
- 2381-9677
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.11646/bde.43.1.19
