Immunocytochemical characterization of astrocytosis along the spinal cord of loop-tail/curly-tail mice with myelomeningocele.

Background: The neurological deficits of myelomeningocele (MMC) have been attributed both to a primary neurulation defect and to a secondary injury of the placode in the intrauterine environment. Since astrocytes are involved in glial scar formation after spinal cord injury, the characterization of astrocyte density along the spinal cord upstream of the MMC can be used as a surrogate marker of the extension of the injury beyond the MMC.

Methods: The curly-tail/loop-tail murine model was applied to obtain newborn mice with MMC. The astrocyte density and topography both at the MMC placode level and at the upper segments of the spinal cord was characterized by immunolabeling using the anti-glial fibrillary acidic protein antibody. This was followed by a qualitative evaluation of immunolabeled cells and morphometric analysis of the samples.

Results: The topography of astrocytes in the spinal cord of MMC newborn mice was compared with that of newborn control mice (without spina bifida aperta) (n = 8/group). The anti-glial fibrillary acidic protein immunoreactivity was significantly increased in the MMC samples in comparison with the normal spinal cord, indicating the presence of an astrocytic response. Increased astrocytosis was also observed in the transitional area located above the MMC. The astrocytosis decreased progressively along the MMC spinal cord until matching the pattern of the control spinal cords. This transitional area involved a segment of the spinal cord with a length of 240 microm in the newborn mouse.

Conclusions: MMC newborn mice show spinal cord injury that is located upstream of the exposed placode and is characterized by proliferation of astrocytes. This finding offers further support for the hypothesis of a tethering mechanism as part of the spinal cord injury observed in MMC newborns.