Renewal of the epithelium in the descending colon of the mouse. I. Presence of three cell populations: Vacuolated‐columnar, mucous and argentaffin

Abstract

Abstract The epithelium of the descending colon was examined in the mouse using one‐micron thick Epon embedded sections of formaldehyde‐fixed tissues stained with the periodic acid‐Schiff and iron‐hematoxylin techniques, and radioautographed at various time intervals after a single injection of tritium labeled thymidine. Four cell types may be described: vacuolated cells located in the lower twothirds of the crypts, columnar cells in the upper third and on the surface, mucous cells and argentaffin (granule‐containing) cells distributed throughout crypt and surface. One hour after injection of 3 H‐thymidine, only some vacuolated and mucous cells are labeled; cells of both types may show mitotic figures, but only in the lower two‐thirds of the crypts. By 36 hours, label appears in cells of the upper third of the crypts; some of these cells are intermediate between vacuolated and columnar, while others are full‐fledged columnar cells. Labeled mucous cells also appear at this level. Occasionally, a labeled argentaffin cell may be found at that time toward the base of the crypts. By three days, labeled columnar and mucous cells are found on the surface. Extrusion of such labeled cells is usually seen toward the fourth day. It is concluded that the epithelium of the descending colon of the mouse includes three cell lines. In the first one, vacuolated cells divide to produce more vacuolated cells, but as they migrate upwards, they lose their vacuoles while ceasing to divide and become typical columnar cells. Together they make up the vacuolated‐columnar cell line . The mucous cells arise from mitosis of cells with a small amount of mucus. As daughter cells migrate upwards, their theca swells, presumably because production of mucus exceeds release, whereas, on the surface, the theca becomes narrow as release predominates. In the third cell line, the argentaffin cells do not divide and appear to originate from poorly differentiated vacuolated cells at the base of the crypts. The latter cells may also give rise to the young mucous cells capable of division. The three cell lines would thus have a common stem cell.