PGP 9.5 immunohistochemistry for axons in plantar hindpaw skin after sciatic nerve injury. Sections of glabrous hindpaw skin in wild-type (Figs. 9a, c and e) and knockout mice (Figs. 9 b and d) illustrating the extent of sensory reinnervation (PGP 9.5 immunopositive axons) after sciatic nerve crush. Figs. 9a and b show sections from uninjured wild-type and knockout mice, and Figs. 9c and d show similar areas of wild-type and knockout mouse skin 17 days after sciatic nerve crush. In the control material the sensory axons are concentrated in the superficial dermis (D) but are not present in the epidermis (E) or in subdermal musculature (M) and their distribution and extent is comparable in both wild-type and knockout mice. Seventeen days after nerve crush a few sensory axons have regenerated into the dermis to about the same extent in both wild-type and knockout animals. Figs. 9e and f are enlargements of the boxed areas in Figs. 9b and d, and illustrate the relative paucity of regenerating PGP 9.5+ axons in the dermis 17 days after sciatic nerve section (e.g. at arrow in Fig. 9f) compared with the dense innervation in control skin (e.g. at arrowheads in Fig. 9e). Bar in Fig. 9a = 100 μm and also applies to b – d; bar in Fig. 9e = 20 μm and applies to f also. Fig. 9g compares counts of PGP 9.5-positive axons in glabrous hindpaw skin 17 days after sciatic nerve crush, in wild-type (N = 6) versus knockout mice (N = 6). There is no significant difference.