Resorption pits formed by CFU-O–derived colonies in the c-kit^high cell population. (A) Cells from a colony developed in the presence of CESJ medium were cocultured with a dentine slice on ST2 cells for 14 days as described in the Materials and Methods section. Pits, indicated by arrowheads, were visualized by staining with Coomassie blue. (B) A control dentine slice incubated only with ST2 cells for 14 days. Multiple dark dots and lines seen throughout the specimen are dentinal tubules, whereas parallel regular lines are saw marks. Scale bars represent 100 μm (A and B).