Fig. 1

(A) Immunostaining for phosphorylated Smad3 (pSmad3) after SCI. Wild-type SC sections at 7, 14, and 21 dpi and uninjured controls are shown. Cross-sections 450 μm from the lesion are shown. A horizontal dotted line at the center of the central canal demarcates dorsal (D) and ventral (V) SC domains throughout the study. Arrows point to pSmad3⁺ nuclei in D SC domains.

(B) pSmad3 quantification in D sections of wild-type SCs. The proportions of pSmad3⁺ cells (percent) were normalized to the total number of nuclei for each section.

(C) pSmad3 and Sox2 immunostaining in wild-type SCs at 7 dpi. Single-channel micrographs are shown in high-magnification views. Arrowheads point to pSmad3⁺ Sox2⁺ progenitors.

(D) pSmad3 quantification in D Sox2⁺ progenitors. The proportions of pSmad3⁺ Sox2⁺ cells (percent) were normalized to the numbers of pSmad3⁺ cells for each section.

(E-G) mstnb expression in wild-type SC sections after SCI. mstnb fluorescence in situ hybridization was followed by immunostaining for Sox2 or HuC/D antibodies. mstnb quantifications in DSC tissues are shown in (E). For these quantifications, the integrated density of mstnb⁺ signals was quantified for each section and averaged across animals. Cross-sections 450 μm from the lesion are shown at 7, 14, and 21 dpi and for uninjured controls in (F). Arrows in (F) point to domains of mstnb expression in D SCs. Dotted ovals delineate central canal edges. High-magnification views of D progenitor domains at 7 dpi are shown in (G).

For all quantifications, SC sections 450 μm rostral to the lesion were analyzed. Sample sizes represent the number of animals quantified and are indicated in parentheses. Error bars depict SEM, and statistical significance was determined by one-way ANOVA. *p < 0.05, **p < 0.01. Scale bars, 50 μm (A–F) and 10 μm (G).