Expression of bcl-2 in enteric neurons in normal human bowel and Hirschsprung disease

The bcl-2 protein has the functional role of blocking apoptosis, ie, programmed cell death. This protein is widely expressed in the developing central and peripheral nervous systems. The purpose of this study was to map bcl-2 expression in the human enteric nervous system, as this has not previously been done.

Rectal specimens were obtained at autopsy of 13 fetuses at 13 to 31 weeks of gestation. Normal colon was also obtained from 5 children and 2 adults, and, in addition, ganglionic and aganglionic bowel resected in 11 patients with Hirschsprung disease was examined. Specimens were fixed in formalin, embedded in paraffin, and analyzed with immunohistochemical methods, using antibodies raised against bcl-2 and neuron-specific enolase (NSE).

The bcl-2 protein was expressed in myenteric and submucous ganglion cells in fetuses, children, and adults. Nerve fibers of the enteric plexuses that were bcl-2 immunoreactive were few compared with the number of NSE-immunoreactive nerve fibers. In aganglionic bowel no bcl-2-or NSE-immunoreactive ganglion cells were revealed. Results of NSE immunohistochemistry showed clearly stained hypertrophic nerve bundles, known to be of extrinsic origin, which were only weakly bcl-2 immunoreactive.

Expression of bcl-2 in enteric ganglion cells of the myenteric and submucous plexuses is displayed in the fetus and during childhood and is also retained in adult bowel. Immunohistochemical analysis of bcl-2 provides a good marker for identification of ganglion cells in Hirschsprung disease and may also be valuable for the diagnosis of disorders characterized by hypoganglionosis or hyperganglionosis.