Raman spectroscopy was used to study temporal molecular changes associated with spinal cord injury (SCI) in a rat model. Raman spectra of saline-perfused, injured, and healthy rat spinal cords were obtained and compared. Two injury models, a lateral hemisection and a moderate contusion were investigated. The net fluorescence and the Raman spectra showed clear differences between the injured and healthy spinal cords. Based on extensive histological and biochemical characterization of SCI available in the literature, these differences were hypothesized to be due to cell death, demyelination, and changes in the extracellular matrix composition, such as increased expression of proteoglycans and hyaluronic acid, at the site of injury where the glial scar forms. Further, analysis of difference spectra indicated the presence of carbonyl containing compounds, hypothesized to be products of lipid peroxidation and acid catalyzed hydrolysis of glycosaminoglycan moieties. These results compared well with in vitro experiments conducted on chondroitin sulfate sugars. Since the glial scar is thought to be a potent biochemical barrier to nerve regeneration, this observation suggests the possibility of using near infrared Raman spectroscopy to study injury progression and explore potential treatments ex vivo, and ultimately monitor potential remedial treatments within the spinal cord in vivo.
Comparative Raman spectra of ex vivo, saline-perfused, injured and healthy rat spinal cord as well as experiments using
enzymatic digestion suggest that proteoglycan over expression may be observable in injured tissue. Comparison with
authentic materials in vitro suggest the occurrence of side reactions between products of cord digestion with
chondroitinase (cABC) that produce lactones and similar species with distinct Raman features that are often not
overlapped with Raman features from other chemical species. Since the glial scar is thought to be a biochemical and
physical barrier to nerve regeneration, this observation suggests the possibility of using near infrared Raman
spectroscopy to study disease progression and explore potential treatments ex vivo and if potential treatments can be
designed, perhaps to monitor potential remedial treatments within the spinal cord in vivo.