Spinal Cord Contusion Research

             The National Spinal Cord Injury Association estimates that 450,000 Americans have a spinal cord injury (AANS). They have also reported that that just over half of this population is made up of young adult (16 to 30 years of age) males and the most common cause for young adult males and females is vehicular collisions (AANS).

One type of spinal cord injury is a spinal cord contusion (or bruise), that is, the crushing of the ventral nerve fibers to the extent that it is severed (Ju et al., 2014). Naturally, the body has evolved an immune response to spinal cord contusions or generally to insults to the CNS. Initially, hemostasis and inflammation occur, and reactive gliosis is triggered. Eventually, an astrocyte scar is formed around the site of injury, functioning as a barrier containing the spread of infection and inflammation-inducing molecules (which would otherwise damage healthy tissue). For the astrocyte scar to form, the proliferation and hypertrophy of astrocytes are triggered, which results in a high concentration of axon-regeneration-inhibiting molecules (Yu & He, 2006). So, the same mechanism that is meant to heal spinal cord contusions also inhibits it. The inhibition of axonal regeneration eventually results in the formation of a cavity in the car and the subsequent collapse of it (Li et al., 2020).

            Due to the body’s flawed response to focal CNS insults, it is not possible to fully heal from contusions to the spinal cord. In a study, Xiaowei Li et al. (2020) investigated a technology that could be used to promote axonal regeneration. The technology that was tested was a nano-hydrogel composite that was developed by Li and their team. The gel was designed to have two main components that distinguish it from previous iterations and allow to promote axonal regeneration; it was designed to have enough rigidity to prevent the collapse of the cavity and to also have sufficient porosity that allows for a microenvironment in which regeneration is possible (Li et al., 2020).

            In a different study, Yi Li et al. (2020) provided evidence that a spinal cord crush injury in mice could be healed without the formation of an astrocyte scar. In depleting the concentration of neonatal microglia in the injury site they found that axonal regeneration is inhibited. This lead them to discover that microglia have 2 crucial roles in the healing of a spinal cord contusion without the formation of an astrocyte scar: “…secrete fibronectin and its binding proteins to form bridges of extracellular matrix…” and “…express several extracellular and intracellular peptidase inhibitors, as well as other molecules that are involved in resolving inflammation”(Li et al., 2020).

References

AANS. (n.d.). Spinal Cord Injury. AANS. Retrieved December 16, 2021, from https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Spinal-Cord-Injury

Ju, G., Wang, J., Wang, Y., & Zhao, X. (2014, April 15). Spinal Cord Contusion. Neural regeneration research. Retrieved December 16, 2021, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4146247/

Li, X., Zhang, C., Haggerty, A. E., Yan, J., Lan, M., Seu, M., Yang, M., Marlow, M. M., Maldonado-Lasunción, I., Cho, B., Zhou, Z., Chen, L., Martin, R., Nitobe, Y., Yamane, K., You, H., Reddy, S., Quan, D.-P., Oudega, M., & Mao, H.-Q. (2020). The effect of a nanofiber-hydrogel composite on Neural Tissue Repair and regeneration in the contused spinal cord. Biomaterials, 245, 119978. https://doi.org/10.1016/j.biomaterials.2020.119978

Li, Y., He, X., Kawaguchi, R., Zhang, Y., Wang, Q., Monavarfeshani, A., Yang, Z., Chen, B., Shi, Z., Meng, H., Zhou, S., Zhu, J., Jacobi, A., Swarup, V., Popovich, P. G., Geschwind, D. H., & He, Z. (2020). Microglia-organized scar-free spinal cord repair in neonatal mice. Nature, 587(7835), 613–618. https://doi.org/10.1038/s41586-020-2795-6

Yiu, G., & He, Z. (2006). GLIAL inhibition of CNS axon regeneration. Nature Reviews Neuroscience, 7(8), 617–627. https://doi.org/10.1038/nrn1956