- Interstitial cells of Cajal (ICC) play a critical role in the control of gastrointestinal motility as pacemaker cells and as regulators of enteric innervation. ICC are one of the first cell types that are injured during an inflammatory process and maintenance of ICC health or promotion of growth and development maybe crucial in recovery after injury. The aim of this study was to evaluate the role of IL-9 in the growth, development and maintenance of ICC in culture. IL-9 in concentrations from 0.02 to 1 microg/ml promoted individual ICC growth and maintenance of the ICC network structure inside tissue explants under culture conditions. The number of ICC grown out of the explants increased significantly at day 4 of culture in the presence of 0.02, 0.5 and 1 microg/ml IL-9. In the presence of 0.5 microg/ml IL-9, explants in culture maintained a higher frequency and stabilized the frequency of spontaneous contractile activity. The ultrastructure of the ICC after 4 days in culture was similar to that in situ. Our data indicate that IL-9 promotes ICC growth in culture and it can be hypothesized that IL-9 is a critical factor in the maintenance of ICC health and ICC repair after injury.