The development and distribution of the interstitial cells of Cajal in the intestine of the equine fetus and neonate.

This study set out to determine the pattern of development and distribution of the interstitial cells of Cajal (ICC) in the intestinal tract of the equine fetus and neonate. Intestinal tissue samples from 12 naturally aborted equine fetuses and three euthanized neonates were collected and fixed in formalin prior to applying standard immunohistochemical labelling techniques targeting the c-Kit protein of the ICC. At 6 months of gestation, a network of ICC was present in the myenteric plexus region of both the small and the large intestine. ICC were also present within the circular muscle layer. In the large intestine, a proximal to distal gradient of distribution was evident, with few ICC observed in the more distal parts of the large intestine in the younger fetuses compared with the near-term animals. A transmural gradient of distribution was also evident within the large intestine, with the most luminal part of the muscularis externa being the last area to be colonized by ICC. This region did not appear fully developed until the early neonatal period. An increased density of ICC was noted throughout the large intestine in the regions of the taenial bands in all animals. This study is the first to describe ICC development and distribution in the equine fetus and neonate.