Wellcome Image of the Month: Mr Muscle

With the Olympics just around the corner, here’s a bit of biology essential for any gold medal-chasing athlete…

This image is a scanning electron micrograph showing three interstitial cells of Cajal (ICC, left) and a single smooth muscle cell (right). The cells have been isolated from the muscle layer of the portal vein, a large blood vessel that supplies the liver with nutrient-rich blood from the gastrointestinal (GI) tract.

ICCs are named after the Nobel laureate Santiago Ramón y Cajal, and are characterised by their irregular shape and several membrane processes branching into secondary and tertiary extensions. Two layers of interstitial cells are found within the muscle layer of the gastrointestinal tract and are involved in generating the spontaneous electrical signals required for gastric movement. This pacemaker activity manifests as a slow-wave electrical rhythm that spreads from the ICC to the smooth muscle cells, leading to muscle contraction of the gut.

These rhythmic electrical signals control the frequency and propagation of gut contractions, forming the basis of peristalsis and segmentation along the gastrointestinal tract. Mice who have had ICC removed from their gastric muscles develop a swollen stomach and prominent bowel obstruction. The loss of interstitial cells in disease may lead to GI disorders such as irritable bowel syndrome and chronic constipation. ICCs are also thought to be the cells from which gastrointestinal stromal tumours (GISTs) arise.

We’re not sure exactly how an Olympian’s interstitial cells can be flexed to improve performance, but regular gastrointestinal flow can’t be a bad thing can it?

References

• Thomsen L, Robinson TL, Lee JC, Farraway LA, Hughes MJ, Andrews DW, & Huizinga JD (1998). Interstitial cells of Cajal generate a rhythmic pacemaker current. Nature medicine, 4 (7), 848-51 PMID: 9662380
• M Kenton, Sang Don Koh Sanders, & Sean M Ward (2006). Interstitial cells of Cajal as pacemakers in the gastrointestinal tract Annual Review of Physiology, 68, 307-343 DOI: 10.1146/annurev.physiol.68.040504.094718

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Image Credit: M Harhun, D Gordienko T Bolton, Wellcome Images