Widespread twi/CNP-EGFP grafts in the shi spinal cord at 4 months of age. (A) Distribution of twi/CNP-EGFP OL/myelin was visible to the naked eye as white patches in the spinal cord of shi mice. Epifluorescence at 488 nm excitation (Insets) corresponds to the white patches, confirming that the myelinating cells were of donor origin. (B) In the cross section of A, the donor OLs/myelin spread over almost the whole white matter, shown by EGFP fluorescence (green), MBP immunolabeling (red), and their merged image. (C) MBP immunolabeling of the thoracolumbar spinal cord of 45-day-old moribund twi, 4-month-old wild-type, and 4-month-old untransplanted shi mice. (D) Toluidine blue myelin staining of the ventral column of thoracolumbar spinal cord. Despite severe demyelination in the 42-day-old moribund twi mouse, the transplanted twi/CNP-EGFP OLs myelinated numerous axons in the shi host. Myelin sheaths were absent in the untransplanted shi mouse. twi/CNP-EGFP OLs myelinated shi axons extensively in the dorsal (E), lateral (F), and ventral (G) columns. (H) Representative electron micrographs from the engrafted ventral column of shi spinal cord. (Inset) A higher magnification of the area indicated with *, showing well compacted myelin. [Scale bars: 1 mm (A), 200 μm (B and C), 20 μm (D), 10 μm (E-G), 5 μm (H), and 200 nm (H Inset).]