Die benignen adenomatösen kolorektalen Polypen gehen mit einem Verlust der noradrenergen und sensiblen Nervenfasern sowie mit einem Anstieg von SP+ Zell-Cluster hervor. Dies führt höchst wahrscheinlich zu einem Übergewicht der SP über Noradrenalin und somit zum Entstehen einer pro-proliferativen und gefäßerweiternden Umgebung. Axonlenkungsmoleküle der sympathischen (SEMA3F) und sensiblen (SEMA3A) Nervenfasern könnten eine wichtige Rolle für den fortschreitenden Verlust der Nervenfasern spielen. Ob die erhöhte Expression dieser Signalmoleküle und der folgende Verlust der Nervenfasern ein frühes Stadium der Polypentwicklung darstellt, sollte ein Schwerpunkt der weiteren Forschung werden.

Background Nerve fibers can exert trophic/anti-trophic effects on epithelial cells. Substance P (SP) is a pro-proliferative neuropeptide, whereas sympathetic noradrenaline is anti-proliferative at high concentrations.

Methods Density of noradrenergic and sensory nerve fibers and presence of nerve repellent factors specific for noradrenergic (semaphorin 3F) and sensory nerve fibers (semaphorin 3A) were investigated in colorectal adenomas.

Key Results The pedunculus was innervated by noradrenergic fibers, whereas the mucosa was sparsely innervated. The control submucosa compared with control mucosa demonstrated increased density of noradrenergic fibers. Control tissue was much better innervated than the polyp. This was accompanied by strong expression of semaphorin 3F in epithelial cells. Density of sensory SP+ nerve fibers was higher in control colon mucosa compared with polyp mucosa, and SP+ cell clusters and semaphorin 3A-positive cells appeared in the intercrypt space in polyps, but not in control tissue.

Conclusions & Inferences This study demonstrated a marked loss of noradrenergic and sensory nerve fibers in polyp mucosa, which was associated with a strong increase of semaphorin 3F and 3A. Up-regulation of the sympathetic repellent semaphorin 3F in the polyps possibly triggers sympathetic repulsion and polyp growth due to the loss of anti-proliferative noradrenaline and presence of SP from local SP+ cells.