Sudan black: a fast, easy and non‐toxic method to assess myelin repair in demyelinating diseases
Recently, by using different high‐throughput in vitro methods, a number of drugs which could potentially enhance remyelination were identified 8. However, these candidate drugs need to be tested in vivo for their remyelination potential prior to clinical investigation in human patients 11.
Myelin sheaths that are thinner than expected for the corresponding axon diameter are often taken as the hallmark of regenerated myelin at the sites of myelin injury 12. The gold standard to demonstrate this is either on toluidine blue‐stained semithin sections or by electron microscopy. Both techniques require plastic embedding, small blocks, and highly toxic substances and are labour intensive. Besides that, immunostainings can be very challenging in plastic embedded tissue. Luxol Fast Blue (LFB), the most commonly used myelin stain, on the other hand is used on paraffin sections, but does not allow single axon resolution in a way that reliably demonstrates remyelinated axons. Hence, in order to efficiently screen for remyelinating candidates in vivo, it would be of great interest to have a staining method that combines optimal resolution of myelin structure with the quickness, simplicity and the large block faces of cryosections. Moreover, the potential to combine such an approach with immunostainings would open new possibilities in dissecting underlying disease mechanisms of neuro‐inflammatory disorders or mode of actions of specific remyelinating drugs.