Autoradiographic localization of [3H]-thymidine incorporation in developing human esophagus

Cell proliferation in the developing human esophagus was investigated by autoradiography using organ culture. The sites of [3H]-thymidine uptake were localized in the epithelium, the mesenchyme, and the muscularis externa of fetal esophageal explants from 10 to 16 weeks of gestation. Proliferating cells were abundant throughout the stratified epithelium at 10 weeks of gestation. Many labeled nuclei in the mesenchyme and the muscular layer were observed. With the development of the stratified columnar ciliated epithelium, a confinement of the proliferating zone in the basal cell layers occurred, and ciliated cells never appeared labeled. The quantitation of proliferating cells showed a labeling index at its highest value between 10 and 12 weeks; this drastically decreased between 12 and 14 weeks' gestation. A similar pattern was noted for the mesenchyme, while the labeling index in the muscularis externa peaked during the 11-14 weeks period. In all fetuses, the highest labeling index was always recorded in the epithelium. The biochemical quantitation of the [3H]-thymidine uptake into the total esophageal DNA clearly supported the continuous decrease of the cell proliferation determined by autoradiography between 10 and 16 weeks of gestation. The present investigation provides for the first time basic quantitative data regarding cell proliferation during a particular developmental phase of the human esophagus.