Klaeyle, L. | bioRxiv Science

bioRxiv2025

A model of apical-out human first trimester trophoblast organoids to study regeneration after syncytial damage

The villous syncytiotrophoblast in humans is the interface between maternal blood and the placenta and its functions are essential for a successful pregnancy. The syncytium can be damaged in vivo focally by high-velocity and turbulent maternal blood flow, or more globally by oxidative stress. It then quickly regenerates, a process critical for the maintenance of placental functions including nutrient transfer and protection from infections. To investigate this process, we developed apical-out trophoblast organoids from first-trimester placentas and induced mechanical damage to the syncytium. We observed spontaneous regeneration of syncytiotrophoblast both morphologically and functionally. TNFRSF12A, the TWEAK receptor, was identified as a potential enhancer of syncytiotrophoblast regeneration. Supplementation with recombinant TWEAK in organoids increased the expression of cell proliferation and fusion markers, promoting syncytiotrophoblast formation. The source of TWEAK was found to be macrophages derived from maternal blood monocytes that adhere to sites of syncytiotrophoblast damage in vivo. This in vitro model that allows the exploration of syncytial biology has relevance for important pregnancy disorders including pre-eclampsia, where breaks occur more often, and vertical infections, where maternal monocytes could be a source of transmission.

developmental biology↗

bioRxiv2025

An organoid model of the menstrual cycle reveals the role of the luminal epithelium in regeneration of the human endometrium

Menstruation is an unusual physiological process whereby the human endometrium undergoes cyclical shedding yet scarless regeneration. Despite its pivotal role in reproductive health, the cellular states and interactions that coordinate this process are incompletely defined. Here, we establish an in vitro menstrual cycle (IVMC) protocol using human endometrial organoids that faithfully recapitulates the epithelium across the key phases of the menstrual cycle including differentiation, hormonal withdrawal, breakdown and regeneration. This IVMC protocol enables intricate study of the early phases of the cycle, which remain difficult to access in vivo. Using this system, we define transcriptional transitions in ciliated and non-ciliated epithelial cells during regeneration, revealing immediate stress-responsive states followed by wound-responsive ones that precede proliferation. We demonstrate that, in response to breakdown, organoids acquire a transcriptomic signature resembling the in vivo luminal epithelium in the menstrual and proliferative phases of the cycle. Luminal epithelial cells are crucial for this re-epithelialization and express factors such as WNT7A which we show to be required for long-term epithelial maintenance. Moreover, cell-cell communication analyses identify luminal epithelium as a signaling hub, interacting with endothelial and immune cells via pathways including CXCL8, consistent with promotion of angiogenesis and immune recruitment during the regenerative window. Taken together, our study establishes a physiologically relevant paradigm to dissect epithelial renewal and cell-cell interactions during menstruation with potential to extend towards modelling common and distressing conditions such as menstrual disorders and endometriosis.

cell biology↗