Neuropeptide-containing nerves in painful hypertrophic human scar tissue

Specimens of hypertrophic scar tissue (n = 9), non-hypertrophic, flat scar tissue (n = 5) and control skin (n = 3) were obtained from eight adult females (aged 22-56) and three adult males (aged 22-59). The specimens were studied histologically and immunohistochemically for vasoactive intestinal polypeptide, neuropeptide Y, calcitonin gene-related peptide, substance P, somatostatin, [Met]enkephalin, [Leu]enkephalin, and the enzyme dopamine beta-hydroxylase. The non-hypertrophic scar tissues were not dissimilar to the control tissue, but contained connective tissue in bundles with a greater number of collagen fibres. In the hypertrophic scar tissue of some patients, the dermis contained adipose tissue displaced upwards from the hypodermis. The connective tissue contained densely packed collagen fibres and fibroblasts; this region was devoid of hair follicles, sweat glands and blood vessels, although they were observed in the region of loosely packed connective tissue. The normal skin contained all the neuropeptides studied, except somatostatin-, and dopamine beta-hydroxylase-immunoreactive nerves, which were seen as single fibres or in nerve bundles, and were associated with blood vessels in the dermis. Neuropeptide Y-immunoreactive nerves were found in the arrector pili muscle, and neuropeptide Y-, vasoactive intestinal polypeptide-, calcitonin gene-related peptide-, [Met]enkephalin- and dopamine beta-hydroxylase-containing nerves were found within sweat glands. In patients with flat, non-hypertrophic scar tissue, neuropeptides and dopamine beta-hydroxylase-containing nerves were absent. In patients with hypertrophic scars, the density of neuropeptide Y-, vasoactive intestinal polypeptide-, substance P-, calcitonin gene-related peptide- and dopamine beta-hydroxylase-immunoreactive nerves was greater in the dermis when compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)