Role of Radial Glia in Transformation of the Primitive Lumen to the Central Canal in the Developing Rat Spinal Cord

Abstract

In the last quarter of the embryonic development of rat and shortly after a termination of neurogenesis, the transformation of the spinal cord primitive lumen (pL) to the central canal (CC) occurs. In this work, we show that this phenomenon is not an insignificant event but it is directly associated with the processes of gliogenesis. Using a light microscopy and immunohistochemistry, we monitored the development of the rat embryonic spinal cord from the end of the neurogenesis on the embryonic day 17 until the maturation of the spinal cord during the first postnatal weeks. Our observations demonstrate the importance of the transformation of the pL to the CC and its connection with gliogenesis, and the mechanism of this transformation is proposed. It is found that a segregation of the glutamate transporter (GLAST) immunopositive cells from the alar plates and transformation of the radial glial cells to the fibrous and protoplasmic astrocytes play presumably a key role in the diminution of the ventricular zone. Results indicate that the very transformation and migration of the radial glial cells during gliogenesis could result in a transformation of the pL to the CC.

Stretching Morphogenesis of the Roof Plate and Formation of the Central Canal

“…4D–I). Thus, the reduction of the primitive lumen and extension of the RP in zebrafish correlates with formation of the GFAP-positive radial scaffold similar to that in mammals [13]. In contrast, the direction of the body curvature in different mutants shows no correlation with the RP extension.…”

“…This process also known as “obliteration” of the primitive lumen was described in cat, mouse and rat [14], [43], [44]. It is accompanied by formation of the dorsal glial septum represented by the RP and other cells [9], [13]. In zebrafish prior to 24 hpf two continuous apical membranes form along the midline and define the inconspicuous primitive lumen or neurocoel extending along all spinal cord [45].…”

“…RP). In contrast, Sevc et al [13] recognized interdependence of RP elongation and conversion of the primitive lumen into the central canal in rat, but suggested that the rearrangement and migration of radial glial cells is behind the transformation of the primitive lumen into the central canal. These authors along with others also recognized a role of two other factors behind conversion of the primitive lumen into central canal: cell proliferation in the neural tube and build-up of axonal pathways.…”

“…While it was shown that the RP elongates during conversion of the primitive lumen into the central canal [9], [13], there are no detailed studies describing this complex process in vivo . Historically, a relationship between the stretching of the RP and conversion of the primitive lumen into the central canal was a matter of some controversy.…”

Regional differences of proliferation activity in the spinal cord ependyma of adult rats

“…Besides the brain, the spinal cord, mainly the central canal (CC) region, also exhibits some limited degree of proliferation activity. Although the most intensive proliferation takes place during embryogenesis and the early postnatal period [2,3], several works brought evidence that cells within the spinal cord ependyma proliferate even in adulthood [4][5][6][7].…”