Decreased Nav1.9 channel expression in Hirschsprung's disease

Voltage-gated sodium channel subtype 9 (Nav1.9) are expressed in dorsal root ganglion neurons and are known to be involved in pain during inflammation. Animal studies have reported Nav1.9 channel expression in myenteric intrinsic primary afferent neurons (IPANs). More recently, a study involving Nav1.9 knockout mice showed clear evidence of colonic dysmotility. However, there are no data regarding the expression of these channels in the human intestine, thus, the aim of our study was to determine Nav1.9 channel expression within the human colon and to elucidate if Nav1.9 channel expression is altered in Hirschsprung's disease (HD).

HD tissue specimens (n=10) were collected at the time of pull-through surgery, while normal controls were obtained at the time of colostomy closure in patients with imperforate anus (n=10). Nav1.9 immunofluorescence was visualized using confocal microscopy to assess the distribution of the protein. Western blot analysis was undertaken to determine Nav1.9 protein quantification.

Confocal microscopy revealed Nav1.9-immunoreactive neurons within the submucosal and myenteric plexus in normal controls, with a reduction in the HD specimens. Calbindin double-labeling showed that Nav1.9-immunoreactive neurons were IPANs. Nav1.9 channels were also seen to be co-localized on smooth muscle cells in all tissues. Western blotting revealed high levels of Nav1.9 protein expression in normal controls, while there was a marked decrease in Nav1.9 protein expression in the HD tissue.

Our results show the expression of Nav1.9 channels within the human colon for the first time. Furthermore, Nav1.9 channel expression is decreased in HD versus normal controls.