Proceedings of The Physiological Society

University of Cambridge (2004) J Physiol 555P, C87


The development of the interstitial cells of Cajal in the equine fetus: an immunohistochemical study

C. Fintl, G.T. Pearson, I.G. Mayhew, S.W. Ricketts* and N.P.H. Hudson

Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh and * Rossdale & Partners, Beaufort Cottage Stables, Newmarket, Suffolk

The interstitial cells of Cajal (ICC) are integral to the coordination of gastrointestinal motility by generating pacemaker activity and mediating neurotransmission in the gastrointestinal tract (Sanders 1996). There is currently no information available on the development of the ICC in the equine fetus. This study was carried out in order to determine whether ICC are detectable in the equine fetus, and if so, whether there are age-related changes in the patterns of ICC distribution, with respect to both the transmural and rostro-caudal distribution of ICC.

Tissues from 12 naturally aborted equine fetuses were used in this study. The ages of the fetuses ranged from 6-11 months (normal gestation length in the horse is 11 months). Sections of ileum, caecal base, pelvic flexure and distal small colon were obtained from each animal. All material was collected at post mortem and was surplus to that required for the routine investigation into the cause of abortion. Collected tissue was fixed in formalin and standard immunohistochemical labelling techniques were applied using an antibody against the c-Kit protein of the ICC (Oncogene Research Products, Cambridge, MA, USA).

ICC were present throughout the equine gastrointestinal tract at 6 months of gestation. The distribution of ICC in the small intestine was similar to that of the neonatal animal while in the large intestine changes were observed during development. A rostro-caudal gradient of immunoreactivity was evident, with the more distal part of the large intestine being less densely colonised by ICC in the younger fetuses compared to the near-term animals. A transmural gradient of ICC distribution was also evident within the large intestine, with the most luminal part of the muscularis externa appearing to be the last area of the intestine to be colonised by these cells. Indeed, even in the full term fetus this region did not appear fully developed compared to the neonatal animal. This transmural gradient observed in the horse does not appear to be present in other mammalian species that have been studied. Considering the proposed location of the pacemaker ICC at the submucosal border of the circular muscle layer (Rae et al. 1998), this may be of importance when investigating commonly observed problems in the equine neonate such as meconium impactions and motility disorders observed in dysmature and premature foals.

This work was supported by the HBLB.

Where applicable, experiments conform with Society ethical requirements