Polyploidy in the murine colonic pericryptal fibroblast sheath

The cause of the apparently paradoxical occurrence of relatively high levels of labelling and low levels of mitotic activity in the pericryptal fibroblast sheath (PCFS) was investigated. Analysis of the distribution of grain densities over epithelial cells and the PCFS in the colon demonstrated that, although the former had a unimodal peak, the PCFS had a multi-peak distribution. The PCFS nuclei with the higher grain densities gradually disappeared with time, due not to proliferation but to lateral migration into the lamina propria. Photodensitometric analysis confirmed the existence of polyploid cells in the colonic PCFS, but not in the epithelium.