Description and basic cell kinetics of the murine pericryptal fibroblast sheath.

The size of the pericryptal fibroblast sheath (PCFS) population was determined by scoring serial sections. There are 38 and 124 PCFS cells per murine small intestinal and colonic crypt, respectively. The cells of the PCFS are slightly weighted towards the lower two-thirds of the crypt in their distribution. The ratio of epithelial cells to PCFS cells is approximately 6.5:1. The in vivo cell kinetics were analysed under control and stressed (fasted-refed) conditions. The control labelling index increases from 8.9% in the small intestine and 7.0% in the colon to peaks 49% and 113% respectively above these values 24 hours after 3HTdR administration. Labelling is observed at all crypt levels equally, and no evidence of vertical migration of labelled PCFS cells was found. Colonic epithelial and PCFS cells show a similar pattern of response to feeding after a fast of 72 hours with respect to time, but a different distribution of response in terms of crypt position.