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Axonal regeneration of RGC is a dream for many. Transcorneal electrical stimulation (TES) may be a great step to the dream. Tagami et al. reported repetitive TES can elongate the axon after the optic nerve crush dependent on the enhancement of IGF-1, whereas the RGC survival was independent from IGF-1. It is interesting that the mechanisms of axonal extension and RGC survival are different in point of IGF-1. In the results, the authors showed only sagittal section of optic nerves. However, they should show the coronal section of optic nerve at the crush site and the evaluated positions. The reasons are follows. 1. In this model, the optic nerve was crushed by the forceps, where the axon damage may vary dependent on the holding site around the optic nerve sheath. The reproducibility of the axon damage in the crush model should be confirmed. Thus, the coronal section will be more impressive compared to the sagittal section. 2. Regenerated site in the optic nerve section should be clarified. Vulnerability against the axon damage may be different in the anatomical structure or vascular factors of the optic nerve in addition to the holding site by forceps.
It should be noted that axonal regeneration is still far from the true reconstruction of the original structure and function. Even if the elongated axons connect to the following nerve, this transmission may be a misdirection often seen after the brain stem infarction. These limitations of TES should be discussed more. Many challenges are still present in TES, but this procedure advances methods for neuroregeneration, in point of its feasibility to apply the stimulation without severe complications and surgical procedure.