Figure 7.

Spinal growth factor treatment in primates ameliorates cortical neuronal atrophy: stereological assessment. A, Retrograde labeling with CTB indicates that a majority of identified layer V corticospinal neurons exhibit a somal area of >500 μm² (see text). B, Frequency distribution of all thionin-stained neurons within layer V. The number of neurons within 100-μm²-sized bins is uniformly reduced after spinal cord injury (red line), and these numbers are restored by BDNF/NT-3 treatment (blue line) compared with intact animals (black line). C, C7 lesions induce a significant reduction in the proportion of large cortical motor neurons (>500 μm²), and treatment with BDNF/NT-3 substantially prevents this neuronal atrophy (NTF graft plus vector: BDNF/NT-3-secreting cell grafts in lesion cavity plus lenti-BDNF and lenti-NT-3 vector injections in host spinal cord parenchyma; NTF graft: BDNF/NT-3-secreting graft in lesion site; ANOVA, p < 0.001; post hoc Fisher's, *p < 0.001). Furthermore, neurotrophin treatment prevents atrophy of a range of layer V somal sizes. D–F, Somal sizes were divided into largest 20% (D), middle 20% (E), and smallest 20% (F). The size of layer V neurons after lesion only were significantly smaller compared with intact monkeys. BDNF/NT-3 treatment prevented the atrophy of both the middle 20% and the smallest 20% and partially prevented atrophy of the largest 20% of neurons. *p < 0.05, intact versus lesion and NTF graft plus vector. Error bars indicate SEM. Scale bar: A, 25 μm.