Vacuole histomorphology characteristics and their same immunophenotype with the gut wall: A histological study using human fetuses.

Background: Intestinal atresia (IA) has been associated with abnormal embryonic intestinal recanalization, a developmental process in which transient vacuoles form and merge with the developing mucosa. This study aimed to investigate the histomorphological characteristics of developing vacuoles and the immunophenotypic similarities between developing vacuoles and the gut wall. Methods: Serial sagittal sections from human fetuses of estimated gestational age (GA) of 8-12 weeks were examined by hematoxylin and eosin (H&E) staining and immunohistochemistry for CK19, CK5/6, and vimentin. Results: A total of eight human fetuses were included in this study. In fetuses at GA 8 weeks, HE staining showed that vacuoles were divided into two components: a peripheral basal compartment and a central luminal compartment, which were separated by a basal membrane. The basal compartment contained a single layer of columnar epithelial cells located on the basal membrane, whereas the luminal compartment contained scattered cells. Few histological changes were observed in fetuses at GA 10 weeks. Immunohistochemical staining showed cytokeratin 19- and cytokeratin 5/6-positive cells in both vacuolar epithelia and gut mucosal epithelium, and they were present continuously, whereas the vimentin-positive cells were present in the luminal compartment of vacuoles, as well as the lamina propria and submucosa of the gut wall. Conclusion: Vacuoles comprise both mesenchymal cells morphologically in the central luminal compartment and epithelial cells in the peripheral basal compartment. The basal compartment of vacuoles and gut mucosal epithelium have the same epithelial immunophenotype; the luminal compartment of vacuoles and the lamina propria and submucosa of the gut wall have the same mesenchymal immunophenotype.