Saturday, 21 February 2015

Imaging Myelination

Turati L, Moscatelli M, Mastropietro A, Dowell NG, Zucca I, Erbetta A, Cordiglieri C, Brenna G, Bianchi B, Mantegazza R, Cercignani M, Baggi F, Minati L.In vivo quantitative magnetization transfer imaging correlates with histology during de- and remyelination in cuprizone-treated mice.NMR Biomed. 2015 Jan 9. doi: 10.1002/nbm.3253. [Epub ahead of print]

The pool size ratio measured by quantitative magnetization transfer MRI is hypothesized to closely reflect myelin density, but their relationship has so far been confirmed mostly in ex vivo conditions. We investigate the correspondence between this parameter measured in vivo at 7.0 T, with staining for myelin fibres, and with myelin basic protein and beta-tubulin immunofluorescence in a hybrid longitudinal study of C57BL/6 and SJL/J mice treated with cuprizone, a neurotoxicant causing relatively selective myelin loss followed by spontaneous remyelination upon treatment suspension. Our results confirm that pool size ratio measurements correlate with myelin content, with the correlation coefficient depending on strain and staining method, and demonstrate the in vivo applicability of this MRI technique to experimental mouse models of multiple sclerosis. 

Imaging myelination and importantly remyelination is one of the road blocks to monitoring repair. Magnetization transfer (MT), refers to the transfer of longitudinal magnetization from the hydrogen nuclei of water (protons) that has restricted motion to the hydrogen nuclei of water that moves with many degrees of freedom. The water with restricted motion is generally conceived as being bound to macromolecules,such as proteins and lipids and hence myelin. Electrophysiology of the optic nerve is the gold standard test for remyelination, but  it is difficult to recruit people  into studies, So using MTR may be an easier option. Lets hope so, otherwise a few remyelination trials will be doomed.

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