Quantitative study of the development and maturation of human oesophageal innervation

By 8 wk gestation, the human fetal oesophagus is identifiable as a hollow epithelium-lined tube with primitive nerve and muscle precursors present. From 8-16 wk gestation, the muscle layers and innervation mature until fetal swallowing commences at 16 wk. This study examines quantitatively the development and maturation of nerve fibres and cell bodies within the oesophagus using histochemistry. Oesophageal samples (n = 35) from 8 wk gestation to 28 months of age and adults (n = 3) were immunostained using antisera for the general nerve marker, protein gene product (PGP 9.5), the glial tissue marker S100, and the synaptic vesicle protein synaptophysin (p38). Histochemical staining for NADH diaphorase enzyme activity was also used to identify neurons. Computer-assisted image analysis of the muscularis externa permitted detailed quantification of cell size, nerve density and myenteric (plexus) fraction. At 8 wk gestation, PGP and synaptophysin were present in immature neurons throughout the cytoplasm, but from 10 wk synaptophysin was localised solely at nerve synapses. S100 immunoreactivity was also detected from 8 wk gestation onwards and was confined to glial tissue. Nerve cell size increased with maturation from 6 microns at 8 wk gestation to 20 microns at term and 21 microns at 28 months. The numbers of cells, nerve density (% area occupied by nerves throughout section) and myenteric fraction (% area occupied by ganglion cells and nerve fibres within the myenteric plexus) all peaked at 16-20 wk gestation and, whereas the number and density then fell towards adult levels, the myenteric fraction fell during the late second trimester and became constant from 30 wk gestation.(ABSTRACT TRUNCATED AT 250 WORDS)