Immunocytochemical Characterization of Astrocytosis along the Spinal Cord of Loop-Tail/Curly-Tail Mice with Myelomeningocele

Abstract

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 µm 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.

Prevalence of supratentorial anomalies assessed by magnetic resonance imaging in fetuses with open spina bifida

“…Similar to the two‐hit hypothesis, which assumes a combination of primary damage in the neural tube and further damage due to exposure of the spinal cord to the intrauterine environment 44 , we propose the concept of a third hit that might be considered for brain anomalies in the context of OSB. Obstructive hydrocephalus secondary to CM‐II could be the key factor for the development of other brain anomalies.…”

Premature Neural Progenitor Cell Differentiation Into Astrocytes in Retinoic Acid-Induced Spina Bifida Rat Model

“…Excitingly, our results suggest that inhibiting NPC differentiation into astrocytes through modulation of Notch/BMP signaling or patterning factors could be a promising neuroprotective strategy. Astrocytosis has been described previously in other spina bifida animal models (Reis et al, 2007(Reis et al, , 2008Oria et al, 2018); however, the response to injury as early as E15 has not been investigated until now. Therefore, the gestation time points chosen (E15, E17, and E20), when comparing groups studied in this report, provide significant knowledge about the timeline of astrocytosis in spina bifida.…”

Hydrogel and neural progenitor cell delivery supports organotypic fetal spinal cord development in an ex vivo model of prenatal spina bifida repair

“…22,[53][54][55][56][57] In our study, we also found minimal glial responses after hydrogel treatment, which is not a trivial finding given that previous histopathologic studies of the MMC placode have shown a paucity of mature neurons but with more extensive gliosis and fibrosis consistent with secondary injury. 58,59 The MMC slice culture model is relatively simple to establish, easy to reproduce, and convenient for observing real-time changes in fetal spinal cord repair and regeneration. Further investigations in this model should allow us to test the effect of different neuroregenerative biomaterials and cell populations on different stages of development of the MMC spinal cord in a more controlled setting than what has been previously attempted.…”

“… 22 , 53 – 57 In our study, we also found minimal glial responses after hydrogel treatment, which is not a trivial finding given that previous histopathologic studies of the MMC placode have shown a paucity of mature neurons but with more extensive gliosis and fibrosis consistent with secondary injury. 58 , 59 …”