IMMUNOHISTOCHEMICAL STUDY OF SKIN REINNERVATION BY REGENERATIVE AXONS

The time sequence of sensory and sudomotor nerve regeneration to the m ouse footpad was studied between one and seven weeks after crush or se ction of the sciatic nerve. Protein gene product 9.5, vasoactive intes tinal peptide, substance P, and calcitonin gene-related peptide were l ocalized in thick sections by using indirect immunofluorescence techni ques and imaged by confocal microscopy. Nerve regeneration was visuall y assessed in all nerves and quantified in sweat glands. After denerva tion, protein gene product 9.5 immunoreactivity remained as dim fluore scence within thick fibers of dermal nerve trunks, whereas thin nerve fibers to sweat glands and to epidermis disappeared. By 14 days postcr ush and 35 days postsection, the first protein gene product 9.5 immuno reactive regenerating axons appeared in large nerve trunks, quickly ex tending to epidermis and sweat glands. Reinnervation of Meissner's cor puscles occurred nearly simultaneous with return of epidermal free ner ve endings and sudomotor network. Calcitonin gene-related peptide, vas oactive intestinal peptide, and substance P immunoreactivity disappear ed completely one week after denervation, then reappeared at 17-18 day s postcrush and 35 days postsection. Fewer nerve fibers were immunorea ctive to these peptides than to protein gene product 9.5. The overall density of reinnervation, although reduced, more closely resembled nor mal in the sweat glands and Meissner's corpuscles than in the epidermi s. Reinnervation was more successful after crush than after nerve sect ion. The time course for functional return of sweating paralleled the return of protein gene product 9.5 immunoreactivity, whereas reappeara nce of vasoactive intestinal peptide was delayed by several days. (C) 1997 Wiley-Liss, Inc.