Growth-associated Protein-43 (GAP-43) Expression In Ganglionic and Aganglionic Colon

Abstract Objectives: Because of its specificity for nerve fibers of the enteric nervous system, calretinin is an effective adjunctive marker in the assessment for Hirchsprung disease. Growth associated protein (GAP-43) has been shown to be expressed in nerve fibers within the intestinal lamina propria. No prior report compares GAP-43 expression in ganglionic versus aganglionic intestine. Methods: Six consecutive Hirschsprung endorectal pull through specimens were retrieved from our archives. In addition 3 controls were selected from colonic resections for reasons other than Hirschsprung Disease. Immunoperoxidase for GAP-43 was carried out on the ganglionic and aganglionic segments of all cases and controls. Submucosal ganglion soma positivity and nerve fiber positivity within the lamina propria were graded on a subjective scale of 1-3 that incorporated both strength and density. Data: GAP-43 strongly stained submucosal ganglion cells and nerve fibers within the lamina propria in 6/6 of the ganglionic segments and 3/3 of the normally innervated controls . GAP-43 did not show any ganglion cell body positivity within the aganglionic segments; however, all 6 aganglionic segment lamina propria were positive for nerve fiber staining. There was a small subjective increase in the amount of nerve fiber positivity for GAP-43 in ganglionic segments and controls versus aganglionic segments. Conclusion: GAP-43 marks mucosal nerve fibers in ganglionic intestine but also aganglionic intestine and thus is less useful than calretinin as a marker for Hirschsprung Disease. The abundant mucosal nerves highlighted by GAP-43 requires further characterization.