Expression of Neural Cell Adhesion Molecule and Polysialic Acid in Cultured Spiral Ganglion Neurons

Purpose: Neural cell adhesion molecules (NCAM) and polysialic acid (polySia) are known to function in cell adhesion and cell migration processes. In neural development, polysialylated NCAM (polySia-NCAM) are closely associated with axon pathfinding, synaptogenesis, neural cell migration, differentiation, and myelination. The purpose of this explorative study was to determine if NCAM and polySia were expressed in spiral ganglion neuron and Schwann cells. Method: Guinea pig spiral ganglion cells were harvested and cultured in vitro. The cells were grown and differentiated in a culture medium together with brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT-3), and glial cell-derived neurotrophic factor (GDNF). After 1 week of growth, the cells were fixed and immunocytochemically stained with antibodies specific for the detection of β-III tubulin, S-100, polySia, and NCAM. Result: In spiral ganglion cultures, the neurons showed staining for β-III tubulin, NCAM, and some of them expressed polySia. S-100 positive glial cells (Schwann cells) showed different levels of NCAM expression, yet no expression of polySia. Some NCAM-positive neurons and Schwann cells showed adhesion to each other. Conclusion: These findings provide further evidence that NCAM may play an important role in neural cell adhesion, myelination, fasciculation, and ganglion formation, but that polySia expression is not obligatory for the adhesive function of adult glial cells. The absence of polySia expression in the adult is consistent with the known neural developmental expression of this glycotope that occurs primarily during the early stages of embryogenesis. The differential expression of NCAM in Schwann cells suggests that their immunocytochemical characteristics and adhesive functions are different than in CNS glial cells, astrocytes, and oligodendrocytes.