The gastrointestinal (GI) tract is a vital organ that digests food, absorbs nutrients, and excretes waste. Normal GI motility is the basis for these functions. The interstitial cells of Cajal (ICC) in the GI muscularis layer promote GI motility together with the enteric nervous system and smooth muscle cells. Since GI motility results from complex coordination of these heterogeneous cells, failure of any one of them can lead to GI dysmotility. Knowledge about ICC in physiological conditions has accumulated in recent decades, while the pathophysiology of ICC in GI inflammatory diseases, such as inflammatory bowel disease, is not well understood. In this review, we summarize the previous studies about the pathophysiological changes of ICC in inflammatory diseases and discuss the inflammatory mediators that induce ICC dysfunction.

Esophageal achalasia is classified into three subtypes according to manometric findings. Since several factors, including clinical characteristics and treatment response, have been reported to differ among the subtypes, the underlying pathogenesis may also differ. However, a comprehensive understanding regarding the differences is still lacking. We therefore performed a systematic review of the differences among the three subtypes of achalasia to clarify the current level of comprehension. In terms of clinical features, type III, which is the least frequently diagnosed of the three subtypes, showed the oldest age and most severe symptoms, such as chest pain. In contrast, type I showed a higher prevalence of lung complications, and type II showed weight loss more frequently than the other types. Histopathologically, type I showed a high loss of ganglion cells in esophagus, and on a molecular basis, type III had elevated serum pro-inflammatory cytokine levels. In addition to peristalsis and the lower esophageal sphincter (LES) function, the upper esophageal sphincter (UES) function of achalasia has attracted attention, as an impaired UES function is associated with severe aspiration pneumonia, a fatal complication of achalasia. Previous studies have indicated that type II shows a higher UES pressure than the other subtypes, while an earlier decline in the UES function has been confirmed in type I. Differences in the treatment response are also crucial for managing achalasia patients. A number of studies have reported better responses in type II cases and less favorable responses in type III cases to pneumatic dilatation. These differences help shed light on the pathogenesis of achalasia and support its clinical management according to the subtype.

Distinct sex differences in the prevalence and symptoms of abnormal bowel habits in patients with irritable bowel syndrome (IBS) have been reported. We have elucidated the sex differences in the regulation of colorectal motility via the central nervous system. Noxious stimuli in the colorectum of anesthetized male rats enhance colorectal motility by activating monoaminergic neurons in descending pain inhibitory pathways from the brainstem to the lumbosacral spinal cord. These monoaminergic neurons release serotonin and dopamine into the lumbosacral spinal cord, resulting in the increment of colorectal motility. In female rats, in contrast, noxious stimuli in the colorectum have no effect on colorectal motility. We clarified that GABAergic inhibition in the lumbosacral spinal cord masks the enhancement of colorectal motility induced by monoamines in female animals. Considering that IBS patients often show visceral hypersensitivity and hyperalgesia, our studies suggest that differences in the descending neurons that respond to painful stimuli are involved in various sex differences in abnormal bowel habits.