Human newborn and adult myenteric plexus grows in different patterns.

Whilst embedded within the gut wall the inaccessibility of the enteric nervous system (ENS) is a major drawback for the establishment of an in vitro model for the human ENS. Using a method which combines collagenase digestion, mechanical agitation and manual dissection it was possible to dissect myenteric plexus from human colon of patients at all ages, from newborn to old-age. While complex networks of ganglia and their interconnecting strands could be isolated from newborn gut, the adult tissue allowed only single or small groups of ganglia to be dissected coherently. Pieces of plexus were cultivated on glass coverslips or on plastic sheets respectively. Explants from newborn or older patients displayed different growth patterns. The cytological behaviour of the newborn explants is characterized by an intensive neurite outgrowth. After 1 to 2 days in culture, glial cells start to leave the explant while proliferating and forming a dense cellular carpet. The axons appear partly arranged in bundles, expanding above the glial carpet. Single neurites can leave the carpet and attach directly on the substrate. Semithin sections and EM studies reveal the existence of numerous neurons within the ganglia. The characteristic dense arrangement of neurons, glial cells and neuropil of the myenteric ganglia in vivo was only partly conserved in newborns while in cultured adult ganglia the cells were sparsely scattered throughout the explant with large clefts between the single cells. The ganglia of the adults do not show any considerable neurite outgrowth, which correlates with the low amount of neurons within the ganglia. The migratory behaviour of the adult glial cells is rather moderate, also the proliferation rate compared to the newborn cultures. In general single cells leave the explant without forming an glial carpet as seen in the newborn cultures. The described method delivers an in vitro paradigm for the study of human myenteric plexus. It underlines the differences in growth pattern, neurite outgrowth and glial proliferation from newborn and older children, as well as from adult patients, thus establishing a base line for future studies.