Figure 1. hGPCs Mediate Robust Myelination after Transplantation into the Adult shiverer Brain.

hGPCs proved both highly migratory and robustly myelinogenic, after delivery at 4–6 weeks of age to the hypomyelinated adult shiverer (MBP^shi/shi) 3 rag2^−/− brain.

(A) By 19–20 weeks of age—13–15 weeks after transplant—the injected cells had dispersed as broadly as is typically observed in similarly transplanted shiverer neonates (Windrem et al., 2008, 2014), with a near-uniform distribution of donor cells noted throughout the forebrain white matter.

(B) hGPCs delivered to myelin wild-type (WT) rag2^−/− mice distributed throughout both gray and white matter, although with less mitotic expansion than that noted in hypomyelinated shiverer recipients.

(C) Oligodendrocyte differentiation and myelinogenesis by donor hGPCs delivered to the shiverer × rag2^−/− brain at 6 weeks of age was robust, with dense myelination of the corpus callosum and fimbria by 19–20 weeks.

(D) A higher power image of (C) shows the high proportion of donor cells in the now humanized host white matter.

(E) Confocal imaging through the callosum of an adult-engrafted shiverer shows a dense array of myelinating human oligodendrocytes. (E’) A higher-power field with orthogonal views.

(F) A single, oligodendrocyte myelinating multiple local axons in its vicinity. CNP, blue; MBP, green; hN, red.

(G and H) Both shiverer (shi) and myelin WT recipients exhibited substantial donor hGPC colonization after adult transplantation, whereas the callosal densities of all human cells (G) and PDGFαR-defined hGPCs (H) were significantly higher in shiverer rather than WT recipients. In the latter, the densities of all donor cells and identified hGPCs (G and H) did not differ between 5 and 12 months of age, suggesting that donor cell expansion in the adult WT brain occurred within the first several months after transplant. *p < 0.05; ***p < 0.001.

(I) The density of transferrin (TF)-defined human oligodendroglia was 5- to 10-fold higher in adult-transplanted shiverers than in WT hosts, when both were assessed 3 months after graft, at 5 months of age. *p < 0.05; ***p < 0.001.

(J) A smaller proportion of the donor cell population matured as GFAP-defined astrocytes; these were significantly more abundant in the shiverer than in WT hosts.

*p < 0.05.

(K–M) Representative images of anti-human NG2-defined donor-derived hGPCs (K), anti-human GFAP-defined astrocytes (L), and TF/human nuclear antigen (hNA) co-expressing donor-derived oligodendrocytes (M), in 19-week-old shiverer white matter, 13 weeks after transplant. Scale bars: 100 μm (C and D) and 50 μm (I–K).