Different distribution of S-100 protein and glial fibrillary acidic protein (GFAP) immunoreactive cells and their relations with nitrergic neurons inthe human fetal small intestine

The appearance, distribution and some histochemical features of non-neurona l cells (NN cells) associated with the myenteric plexus of human fetal smal l intestine have been studied by means of S-100 protein and GFAP immunocyto chemistry between the 10th and 17th week of gestation. In addition, double labelling immunocytochemistry using an antibody raised against a constituti ve isoform of nitric oxid synthase (bNOS) in combination with an S-100 prot ein antibody was applied to investigate the morphological relations between NN cells and nitrergic neurons in the developing gut wall. Cells with immu noreactivity for both glial-specific proteins are already present in the 10 th week of gestation. While cells with S-100 protein immunoreactivity are l ocated within the circular muscle layer as well as in the myenteric, and su bmucous plexuses, cells with GFAP immunopositivity are mainly restricted to the side of the myenteric plexus adjacent to the longitudinal muscle layer . In contrast to the dense network formed by S-100 protein immunopositive s tructures the GFAP immunopositive cells appear singly and do not connect in to a network. Double-labelling immunocytochemistry reveals nitrergic fibers (NOS-IR) in close relation to the S-100 protein immunoreactive glial netwo rk. NOS-IR varicosities are in close association with the surface of those cells both in the circular muscle layer (CM) and in the tertiary plexus. It is concluded that two populations of NN cells with different locations and different immunohistochemical characters appear and develop together with the enteric ganglia in the human fetal intestine. The close morphological r elation of NOS-IR fibers with S-100 protein immunopositive cellular network indicate a functional relationship between S-100 protein immunopositive ce lls and the nitrergic nerves during the early development of human enteric nervous system (ENS).