Morphologic changes in the cytoskeleton and adhesion apparatus during the conversion from pseudostratified single columnar to stratified squamous epithelium in the developing mouse esophagus

Mammalian esophageal stratified tissue homeostasis is maintained distinctively by the epithelial pluripotent p63+Sox2+ and p63-Sox2+ cell populations

Self-renewing, damage-repair and differentiation of mammalian stratified squamous epithelia are subject to tissue homeostasis, but the regulation mechanisms remain elusive. Here, we investigate the esophageal squamous epithelial tissue homeostasis in vitro and in vivo. We establish a rat esophageal organoid (rEO) in vitro system and show that the landscapes of rEO formation, development and maturation trajectories can mimic those of rat esophageal epithelia in vivo. Single-cell RNA sequencing (scRNA-seq), snapshot immunostaining and functional analyses of stratified "matured" rEOs define that the epithelial pluripotent stem cell determinants, p63 and Sox2, play crucial but distinctive roles for regulating mammalian esophageal tissue homeostasis. We identify two cell populations, p63+Sox2+ and p63-Sox2+, of which the p63+Sox2+ population presented at the basal layer is the cells of origin required for esophageal epithelial stemness maintenance and proliferation, whereas the p63-Sox2+ population presented at the suprabasal layers is the cells of origin having a dual role for esophageal epithelial differentiation (differentiation-prone fate) and rapid tissue damage-repair responses (proliferation-prone fate). Given the fact that p63 and Sox2 are developmental lineage oncogenes and commonly overexpressed in ESCC tissues, p63-Sox2+ population could not be detected in organoids formed by esophageal squamous cell carcinoma (ESCC) cell lines. Taken together, these findings reveal that the tissue homeostasis is maintained distinctively by p63 and/or Sox2-dependent cell lineage populations required for the tissue renewing, damage-repair and protection of carcinogenesis in mammalian esophagi.

Cerebrospinal fluid may flow out from the brain through the frontal skull base and choroid plexus: a gold colloid and cadaverine injection study in mouse fetus

PURPOSE

It has been commonly accepted for a long time that the cerebrospinal fluid (CSF) drains into arachnoid granulations from the subarachnoid space to the dural venous sinus unidirectionally. However, recently, periventricular capillaries and lymphatic concepts have been introduced. The CSF moves along the perivascular space and drains into the capillary vessels or meningeal lymphatic tissues. CSF is involved in removing brain waste out of the brain. In this study, we investigated the outflow mechanism of substances in the CSF from the brain.

METHODS

We investigated the movement of CSF by injection of gold colloid conjugates (2, 40, and 200 nm) into the lateral ventricles of mouse fetuses and evaluated the deposition by silver stain with tissue transparency and electron microcopy. Cadaverine was also injected into the lateral ventricle to determine its movement tract.

RESULTS

The gold particle deposition was mainly observed in the frontal skull base. Electron microscopic study showed that the gold particle deposition was observed on the choroid plexus and ependyma in the lateral ventricle and also red blood cells in the heart and liver. Two-nanometer particles were exclusively observed in the liver. Cadaverine injection study demonstrated that cadaverine was observed at the extracranial frontal skull base, choroid plexus, ependymal surface, and perivascular area in the brain white matter.

CONCLUSION

The particles in the CSF were shown to move from the brain to the frontal skull base and also into the blood stream through the choroid plexus in the fetus. The outflow of particles in the CSF may be regulated by molecular size. This new information will contribute to the prevention of brain degeneration due to brain waste deposition.

Histomorphometric analysis of the epithelial lumen, mesenchyme, smooth muscle cell layers, and mesentery of the mouse developing duodenum in relation with the macroscopic morphogenesis

Integral analysis of the development of the epithelium, mesenchyme, and smooth muscle cell (SMC) layers, i.e., the inner circular (IC) and outer longitudinal layers, as well as their relation with the mesentery is necessary to understand macroscopic gut development. We here focused on the proximal duodenum with the characteristic "C"-shaped loop and analyzed the duodenum down to the duodenojejunal flexure in C57BL/6J mouse embryos at embryonic days (E) 13.5, 15.5, and 17.5 by histomorphometric analysis. We examined the angle of the axis of the epithelial lumen, which was oval at E13.5 against the mesentery, along with the epithelial cell nuclear shape, the adjacent mesenchymal cell density in relation to the epithelial lumen axis, and the development of SMC layers. The luminal axis of the oval epithelial lumen at E13.5 rotated clockwise against the mesentery in the proximal duodenum. The shape of epithelial nuclei was longer and thinner at the long axis but shorter and broader at the short axis, whereas mesenchymal density was significantly lower in the area on the luminal long axis than that on the short axis. The number of SMC layers in the IC at E13.5, E15.5, and E17.5 showed a regional difference in relation to the mesentery, but no regional difference along the long axis of the duodenum. These findings suggest that epithelial lumen winding against the mesentery and the corresponding changes in the epithelial cell shape and surrounding mesenchymal density may be involved in the formation of the "C" loop of the proximal duodenum.