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The occurrence of S100 proteins in neurons of the mammalian peripheral nervous system is still controversial. This study was designed to investigate this topic in dorsal root ganglia (DRG) and the enteric nervous system (ENS) of several mammalian species (horse, buffalo, cow, sheep, pig, dog, rabbit and rat), as well as in DRG, paravertebral sympathetic ganglia (SG) and ENS of the adult man. Rat embryos of E17 and E19 were also examined. The material was fixed in Bouin's fixative, paraffin-embedded and processed for immunohistochemistry, combined with image analysis, using a panel of mono and polyclonal antibodies against S100alpha, S100beta or S100alpha + beta (referred to here as S100) proteins. In all species examined, strong S100 protein immunoreactivity (IR) was found in satellite glial cells and Schwann cells, which also showed S100alpha and S100beta IR in humans. Furthermore, faint S100 protein IR was observed in a subpopulation of DRG intermediate- and large-sized sensory neurons in humans, buffalo, sheep, and pig. The rat was the only species showing clear S100 and S100beta in neurons, labelling in about 30-35% in adults (small, intermediate and large in size), and about 88% at E17 and 42% at E19, respectively. Weak S100alpha protein IR was observed in most of human SG neurons. In ENS, S100 protein IR was restricted to enteric glial and Schwann cells, with the exception of cow and goat in which a subset of neurons in both the myenteric and submucous plexuses displayed strong S100 protein IR. Neuronal S100alpha IR and glial S100beta IR was found in the human ENS. The present results demonstrate intra- and inter-specific differences in the expression of S100 proteins by neurons of the peripheral nervous system among mammalian species. Furthermore, they also suggest that neuronal S100 protein, at least in humans, consists of both S100alpha and S100beta.

This study was aimed at analyzing the changes in cutaneous sensory corpuscles from the territory of lesioned nerves and clinically denervated skin of patients with spinal cord injury using immunohistochemical methods. The morphological and biochemical characteristics of the Schwann-related cells of the mature sensory corpuscles (lamellar cells of Meissner corpuscles and inner-core of Pacinian corpuscles) depend upon the axon. To clarify whether this dependence requires structural and/or functional integrity of sensory axons we analyzed immunohistochemically some axonal, Schwann cell and perineurial cell antigens in cutaneous sensory corpuscles from i) the underlesional levels of patients with spinal cord injury affecting dorsal and lateral funiculi; ii) peripheral nerve entrapment, iii) sectioned and grafted nerves. Skin biopsy samples from the hand or feet were processed for peroxidase-antiperoxidase immunohistochemistry using monoclonal antibodies directed against neurofilament proteins (to label the axons), S-100 protein (to label Schwann-related cells), epithelial membrane antigen (to label the perineurial derivatives), vimentin (to label both Schwann cell and perineurial derivatives). Meissner and Pacinian corpuscles of subjects suffering from spinal cord lesions showed an immunohistochemical profile close to normality, although in many of them S-100 protein was unevenly distributed or absent. Sensory corpuscles of the cutaneous territory of entrapped nerves were in most cases similar to those of normally innervated skin. The most striking finding in these subjects was the hyperinnervation of blood vessels and sweat glands. Finally, nerve section and subsequent unsuccessful graft repair resulted in absence of immunostaining for all the assessed antigens in sensory corpuscles. The present results suggest that structural, but not functional, integrity of the axon is essential in maintaining some immunohistochemical characteristics of the human cutaneous sensory corpuscles. Morphological findings are correlated and discussed in relation to the clinical evaluation of the sensitivity.