Element imaging in formalin fixed slices of human mesencephalon

The scarcity of native frozen pathological and healthy human brain tissue is actually one of the major bottlenecks concerning the investigation of neuropsychiatric diseases. Therefore it is of some interest to make formalin fixed tissue specimens accessible to mass spectrometric analytical techniques. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and matrix matched standards were employed to generate quantitative element maps of human mesencephalon slices that had been stored in formalin for more than 10 years of a single subject. The characteristic distribution patterns of Cu and Zn were completely blunted but Fe was clearly enriched in the substantia nigra (SN) – especially in the matrix of the pars compacta – and the nucleus ruber (NR) at concentrations of 179 μg g−1, 231 μg g−1 and 187 μg g−1 (wet weight), respectively, very similar to literature values obtained from homogenates of fresh tissue. Mn and Ca congruently reflected the distribution of melanised SN neurons. Interestingly, the distribution of Pb was congruent to that of Fe reaching 0.8 μg g−1 in the SN, 1.1 μg g−1 in the matrix and 0.9 μg g−1 in the NR. Images of C and P reflected the gray matter-white matter partition of the tissue. These results suggest that a meaningful quantitative assessment of Fe, Mn and Pb is possible in tissue samples which have previously been stored in buffered formalin solution.

Quantitative element maps of formalin fixed sections of one human mesencephalon were generated using bioimaging by laser ablation inductively coupled plasma mass spectrometry.Figure optionsDownload high-quality image (192 K)Download as PowerPoint slideHighlights
► LA-ICP-MS imaging of formalin fixed tissue yielded specific element distributions of Fe, Mn, Pb, Ni and Ca while Cu and Zn were washed out.
► Concentrations of Fe, Mn, were similar to those reported for fresh tissue.
► Fe and Pb follow a matrix-nigrosome distribution while Mn and Ca colocalize with clusters of melanised cell bodies.