Oral Presentation ESA-SRB-NZSE-CaSR 2026 in conjunction with ENSA

Modified hESC-derived placentoid cultures form structures with primitive syncytium-like characteristics  (144068)

Matilda Janssen 1 , Ashley Williams 1 , Georgia Kafer 1
  1. School of Health, University of the Sunshine Coast, Moreton Bay, QLD, Australia

1.Introduction 

The primitive syncytium is the first syncytiotrophoblast (STB) lineage to form during early placentation, arising from primitive cytotrophoblast (CTB) at the maternal-fetal interface. Primitive syncytium establishment is essential for successful pregnancy, yet it is among the hardest stages to model in vitro as trophoblast organoids and stem cell-systems poorly recapitulate primitive syncytium and early villous formation1-3. We set out to evaluate whether placentoids derived from human embryonic stem cells (hESCs) on topographically patterned scaffolds could form primitive syncytium-like structures.  

 

2.Methods 

Human ESCs were seeded onto polydimethylsiloxane (PDMS;1:10) scaffolds patterned with ‘villous’ areas and flat regions. Cells were primed for differentiation in StemPro-based minimal medium (EMIM) supplemented with basic fibroblast growth factor (12ng/mL), then transdifferentiated into trophoblast lineages using EMIM with BMP4 (10ng/mL), SB431542 (20µM), and SU5402 (20µM). All cultures were maintained in a humidified environment (5% CO2 in atmospheric (20%) O2). Trophoblast markers and markers of apoptosis and oxidative stress were profiled at differentiation days 4, 7 and 14 by western blot (iBright 1500). In parallel, placentoids were fixed (4% paraformaldehyde) and cellular architecture was assessed using immunofluorescent imaging (Olympus FV3000 , APX100). 

 

3.Results 

Human ESC-derived placentoids formed primitive syncytium-like structures at day 14. Western blotting (n=3) revealed gradual expression of STB (SDC1) and CTB markers (ITGA6) across placentoids maturation. Oxidative stress (Thioredoxin) also increased as placentoids matured, but we observed no indication of apoptosis (Cleaved Caspase 3) at any day assayed. Immunofluorescent imaging of day 14 placentoids (n=3) revealed primitive syncytium-like outgrowths preferentially occurring on flat PDMS regions, with typical ‘mature’ placentoids maintained on ‘villous’ areas. 

 

4.Conclusion 

We present evidence that altering the topography of placentoid scaffolds can alter placentoid architecture. These results suggest that we can tune in vitro methods to generate placentoid models to interrogate currently unanswered questions about human placental development and function.  

  1. Joshua J Fisher, Ashley Williams, Farhad Soheilmoghaddam, Georgia R Kafer, Advantages, limitations, and innovative considerations for established and emerging models of human placental syncytiotrophoblast, Human Reproduction Update, Volume 32, Issue 3, May-June 2026, Pages 333 355, https://doi.org/10.1093/humupd/dmaf034
  2. Haider S, Meinhardt G, Saleh L, et al. Self-renewing trophoblast organoids recapitulate the developmental program of the early human placenta. Stem Cell Reports. 2018;11(2):537-551. doi:10.1016/j.stemcr.2018.07.004
  3. Turco MY, Gardner L, Kay RG, et al. Trophoblast organoids as a model for maternal-fetal interactions during human placentation. Nature. 2018;564(7735):263-267. doi:10.1038/s41586-018-0753-3