Tissue degeneration in ALS affected spinal cord evaluated by Raman spectroscopy with 457 nm excitation

The Raman spectral features from spinal cord tissue sections of transgenic, ALS model mice and nontransgenic mice were compared using 457 nm excitation line, profiting from the favourable signal intensity obtained in the molecular fingerprint region at this wavelength. Transverse sections from four SOD1G93A mice at 75 days and from two at 90 days after birth were analysed and compared with sections of similarly aged control mice. The spectra acquired within the grey matter of tissue sections from the diseased mice is markedly different from the grey matter signature of healthy mice. In particular, we observe an intensity increase in the spectral windows 450-650 cm-1 and 1050-1200 cm-1, accompanied by an intensity decrease in the lipid contributions at ~1660 cm-1, ~1440 cm-1 and ~1300 cm-1. Axons demyelination, loss of lipid structural order and the proliferation and aggregation of branched proteoglycans are related to the observed spectral modifications. Furthermore, the grey and white matter components of the spinal cord sections could also be spectrally distinguished, based on the relative intensity of characteristic lipid and protein bands. Raman spectra acquired from the white matter regions of the SOD1G93A mice closely resembles those from control mice.