Appearance of interstitial cells of Cajal in the human midgut.

Several subtypes of the interstitial cells of Cajal (ICC) form networks that play a role in gastrointestinal motor control. ICC express c-kit and depend on signaling via Kit receptors for development and phenotype maintenance. At 7-8 weeks of development, c-kit-immunoreactive (c-kit-IR) cells are present in the human oesophagus, stomach and proximal duodenum wall. In the remaining small and large bowel, c-kit-IR cells appear later. The object of the present study is to determine the timing of the appearance of c-kit-IR ICC in the parts of the digestive tube originating from the midgut (distal duodenum, jejunum, ileum and proximal colon). Specimens were obtained from eight human embryos and 11 fetuses at 7-12 weeks of gestational age. The specimens were exposed to anti-c-kit antibodies to investigate ICC differentiation. The differentiation of enteric neurons and smooth muscle cells was immunohistochemically examined by using anti-PGP9,5 and anti-desmin antibodies, respectively. In the distal duodenum, jejunum and ileum, c-kit-IR cells emerged at week 9 at the level of the myenteric plexus in the form of a thin row of cells encircling the inception of the ganglia. These cells were multipolar or spindle-shaped with two long processes and corresponded to the ICC of the myenteric plexus. In the proximal colon, c-kit-IR cells emerged at week 9-10 in the form of two parallel belts of cells extending at the submucosal plexus and the myenteric plexus levels. We conclude that ICC develop following two different patterns in the human midgut.