Immunohistochemical Study on Localization of Tenascin in the Cervical Region of Rat Spinal Cord During Development.

Abstract

Tenascin (TN) is transiently expressed in some organs and tumors at various developmental stages. It has also been reported that tenascin was a major extracellular matrix component in a developing nervous system, and played an important role in neurite outgrowth and pattern formation of the cerebral and cerebellar cortices.In the present study, we examined, under light and electron microscopes, the localization of TN in the cervical region of rat spinal cord during the late prenatal and early postnatal stages by means of conventional and immunohistochemical methods. In the specimens stained with hematoxylin-eosin and thionin, the following results were obtained: the structure of spinal cord was developing at the postnatal stages and attained a definite form around the 5th day after birth. Nissl bodies in neurons were maturing during this period and the processes of neurons elongated toward white matter. Concomitantly, neuroglia were also increased in the white matter.In accordance with it, luxol fast blue (LFB) and sudan black B stainable substances appeared in the white matter, especially ventral and lateral funiculi around the 5th day of age.The results of immuno-light microscopical observation showed that TN-labeling was observed only in the gray matter of the spinal cord at the 18th day of gestation, but both in gray and white matters from the 20th day of gestation to the 5th day after birth. The most intense TN-labeling was detected in the boundary of gray and white matter in the ventral and lateral funicili at the 2nd to 5th day after birth. As the development proceeded, up to the 2nd week after birth, TN-labeling was mainly distributed in the white matter except for the ventral region of dorsal funiculus and almost completely disappeared from the gray matter. Here, it was also noticed that the ventral region of dorsal funiculus became stainable with LFB or sudan black B between the 2nd and 3rd week after birth and at the same stage of development, TN-labeling became detectable in this region.At the electron microscopical level, TN-labeling was detected in the intercellular spaces of the gray matter during the 1st to 10th day of age. That is, TN was expressed associating with the cytoplasmic membrane and processes of neurons and neuroglia. TN-labeling was also observed along the cytoplasmic membrane of myelinating oligodendrocytes and in the cytoplasm of neuroglia, especially oligodendrocytes in the white matter at the 10th day to the 2nd week after birth. Clear reaction products for TN could not be detected in the synaptic region.From this evidence, it is concluded that TN mediates the interaction of neuron and neuroglia during late prenatal and early postanatal stages and plays an important role in elongation of neuronal processes and migration of neuroglia as well as the myelination in the developing rat spinal cord.