Interstitial cell of Cajal

Overview
The Interstitial cell of Cajal (ICC) is a type of cell found in the gastrointestinal tract. It serves as a pacemaker that triggers gut contraction.

Many types of smooth muscle tissues have now been shown to contain ICC, but with few exceptions the function of these cells is not known and an area of active research. An international society (International Society for ICC, www.isicc.org) has recently been formed to provide a forum to discuss research in ICC in a variety of tissues.

Role in slow wave activity
ICC serve as electrical pacemakers and generate spontaneous electrical slow waves in the gastrointestinal (GI) tract. Electrical slow waves spread from ICC to smooth muscle cells and the resulting depolarization initiates calcium ion entry and contraction. Slow waves organize gut contractions into phasic contractions that are the basis for peristalsis and segmentation.

Frequency of ICC pacemaker cells
The frequency of ICC pacemaker activity differs in different regions of the GI tract:
 * 3 per minute in the stomach
 * 12 per minute in the duodenum
 * 10 per minute in the ileum
 * 3 per hour in the colon

ICC also mediate neural input from enteric motor neurons. Animals lacking ICC have greatly reduced responses to the transmitter, acetylcholine, released from excitatory motor neurons, and to the transmitter, nitric oxide, released from inhibitory motor neurons. Loss of ICC in disease, therefore, may interrupt normal neural control of gastrointestinal (GI) contractions and lead to functional GI disorders, such as irritable bowel syndrome.

ICC also express mechano-sensitive mechanisms that cause these cells to respond to stretch. Stretching GI muscles can affect the resting potentials of ICC and affect the frequency of pacemaker activity.

ICC are also critical in the propagation of electrical slow waves. ICC form a network through which slow wave activity can propagate actively. If this network is broken, then 2 regions of muscle will function independently.

Pathology
ICCs are thought to be the cells from which gastrointestinal stromal tumours (GISTs) arise. Also, abnormalities in the ICC network is one cause of chronic intestinal pseudo-obstruction.

Eponym
The interstitial cells of Cajal are named after Santiago Ramón y Cajal, a Spanish pathologist and Nobel laureate.