Restitution of single-cell defects in the mouse colon epithelium differs from that of cultured cells

1 Department of Clinical Physiology and 2 Department of Gastroenterology, Charité, Campus Benjamin Franklin, Berlin; and 3 Jena University of Applied Sciences, Jena, Germany Submitted 30 June 2005 ; accepted in final form 5 January 2006 Integrity of colon epithelium is of crucial importance and, as small defects occur constantly, rapid repair (restitution) is essential. To investigate the mechanism of restitution, single-cell lesions were induced in mouse colonic surface epithelia by iontophoretic injection of Ca 2+ . Closure of the resulting defects was monitored using confocal laser scanning microscopy (CLSM), and functional sealing by electrophysiological techniques. Restitution was evaluated as the time constant of the exponential decrease in conductance of an induced leak and amounted to 0.28 min under control conditions. After 4 min, the leak was completely sealed. Repair was thus considerably faster than in previously investigated HT-29/B6 cells ( = 5.73 min). As in cultured cells, cytochalasin D delayed restitution in native colon epithelia ( = 0.69 min), indicating the involvement of actin in the healing process; however, no accumulation of actin surrounding the lesion was detected. Long-term incubation of epithelia with IFN- alone or in combination with TNF- increased to 0.49 and 0.59 min, respectively. In contrast to cultured cells, TNF- alone did not affect restitution. A brief (