Do astrocytes participate in rat spinal cord myelination?

Astrocytes play an important role in CNS development phenomena, such as neuron migration and blood-brain barrier formation, but only a little is known of their role in the process of myelination. The aim of our investigation was to examine the relationship between astrocytes and myelin formation. We evaluated rat spinal cords using hematoxylin-eosin and Klüver-Barrera staining methods as well as immunohistochemical methods with antibodies against myelin basic protein (MBP), glial fibrillary acidic protein (GFAP) and lamins A/C and B2. Our investigation revealed that myelination in the rat spinal cord tracts began between the 6th and 9th postnatal day involving the anterior funiculi, then the lateral funiculi and later the posterior ones. The process of myelination finished about the 25th postnatal day. More GFAP immunoreactive astrocytes were detected in parallel to the increase of MBP reactivity. We suggest that the temporary increase of GFAP positive cells accompanying the process of myelination is necessary for normal myelin development and may be connected with local secretion of growth factors by astrocytes.