Morphogenetic maturation of chicken chorioallantoic membrane (CAM) and its disruption by tumor xenografts.
Journal
Developmental biology
Journal Volume
529
Start Page
154
End Page
166
ISSN
1095-564X
Date Issued
2026
Author(s)
Ismagulov, Galym
Takahashi, Yukie
Ishiyama, Eri
Ogasawara, Katsutoshi
Sakai, Keiichi
Chan, Yat Nok
Fukuda, Takaichi
Sheng, Guojun
Abstract
Chorioallantoic membrane (CAM) functions as embryonic "lung" in birds/reptiles and forms through fusion of the chorion and allantois, two extraembryonic membranes conserved in amniotic vertebrates. Modified CAM gives rise to the placenta, performing similar roles in mammalian development. Despite its importance, cellular morphogenesis leading to CAM maturation is poorly understood. In particular, it is unclear how mesoderm-derived capillary cells are positioned within the chorionic ectoderm layer in mature CAM. In this work, using a combination of live imaging, histology, immunofluorescence and electron microscopy approaches, we carried out a systematic analysis of chicken CAM morphogenesis from embryonic day 4.5 (D4.5; soon after its initial formation) to D15 (when it reaches its fully mature architecture). We show that CAM chorionic ectoderm establishes physical contact with the acellular soft shell from D7.5. CAM mesoderm-derived capillary vessels shift from a sub-chorionic ectodermal position to an intra-chorionic ectodermal one from D11 onward. This is mediated by the downward movement of a subset of chorionic ectoderm cells (termed chorionic basal cells) from D9 through inter-capillary spaces, eventually enveloping all superficial capillaries basally and leading to a seemingly mesoderm-out/ectoderm-in topology. All CAM superficial capillary vessels are covered by a thin layer (<1 μm) of chorionic ectodermal cell (capillary covering cell) processes. Another type of superficial chorionic ectodermal cell (villous cavity cell) contains numerous apical villi. Detailed immunofluorescence and electron microscopy studies revealed that germ layer organization and epithelial cell polarity were maintained during CAM morphogenesis and maturation. Heterogeneity in CAM ectoderm, mesoderm and endoderm cells was observed. Cell proliferation was seen in all three germ layers during early maturation, but became more prominent in chorionic basal cells during later maturation. CAM-tumor graft data suggested that this mature CAM architecture could be modulated as a result of dynamic host-graft tissue interactions.
SDGs
Type
journal article