Vibrational spectroscopy methods reveal biochemical changes associated with the glial scar formation after traumatic brain injury.

Traumatic brain injury (TBI) is a serious clinical and social problem. Millions of TBI cases, that require hospitalization and consequently burden social security systems, are reported each year. Analysis of the time course of changes that occur in the brain after primary injury may help indicate therapeutic goals and treatment directions that will minimize severe secondary effects of TBI. Existing animal models simulating the development of TBI in human are divided into two main groups, namely into diffuse and local models. Diffuse injury models are ideal for studying concussions and long-term effects of TBI, as they replicate global changes occurring in brain. Local injury models excel in examining focal brain damage and testing region-specific therapies, they also offer greater control and reproducibility. In our study local induction of TBI enabled better control of the extent of the damage and thus reduced the number of animals needed for the experiment. As part of the work, Fourier transform infrared microspectroscopy and complementary Raman microscopy were used to track the time course of biochemical changes that occur in the rat cerebral cortex as a result of its local mechanical damage. Comparative studies, carried out for the injury site and microscopically unaffected area of the cerebral cortex, indicated some anomalies in the accumulation and structure of organic compounds, including a reduction of the level of cholesterol/cholesterol esters (approx. 30 % in first two examined periods after TBI) and the compounds containing phosphate groups (approx. 25 %), as well as the conformational changes of proteins and lipids in the injury site comparing to unchanged cortex tissue. The comparison of the glial scar development in male and female rats showed only a very subtle differences between sexes. Among them it is necessary to mention the diminished unsaturation degree of lipids within the scar in case of female rats that was not found in males. The obtained results substantiated that vibrational microspectroscopy methods represent powerful, non-destructive tool of high-resolution biomolecular analysis of brain tissue. These techniques enable the identification of biochemical alterations linked to glial scarring following TBI, allow for the monitoring of the dynamics of this process, and provide insights into the sex-dependence of the recorded anomalies. This knowledge could prove instrumental in identifying potential diagnostic and prognostic biomarkers of TBI, as well as in the development of new therapeutic strategies for managing this condition.