Confocal raman microspectral imaging of ex vivo human spinal cord tissue

Abstract

Confocal Raman microspectral imaging (CRMI) provides a versatile tool to illustrate the biochemical nature and structure of biological tissue without introducing any external labels. In this work, a precise correlation was established between the biochemical profile and histological architecture of ex vivo human spinal cord tissue by using CRMI with 633nm excitation. After precisely linking the spectral features to the chemical constituents, much information about the molecular composition of both gray and white matter were revealed. Two-dimensional Raman images were generated by integrating the intensities of the characteristic Raman bands in the area of the intermediate column and ventral horn. K-mean cluster analysis was further applied to visualize the underlying morphological basis of spinal cord tissue by chemical component types and their distribution pattern. Lipid-rich white matter could be visually distinguished from gray matter considering a CH2 bending/scissoring band at 1445cm−1 and an amide III band at 1250cm−1. Meanwhile, the formation and distribution pattern of perineuronal nets (PNNs) in the scanning area was validated by the integration of saccharides (617cm−1) and amide III bands. Moreover, the heme profile indicated a higher degree of vascularization in gray matter. All of the results obtained testified to the possibility that gray matter could be more susceptible to spinal cord injury (SCI) because of capillary network distribution and glycosaminoglycans (GAGs) aggregation. These findings are important for interpreting the morphological specificity of human spinal cord tissue, and also for studying the molecular basis of SCI.