Morphology and Cell Proliferation of Subepithelial Fibroblasts in Adult Mouse Jejunum: II. Radioautographic studies

Abstract

Cell proliferation and migration of subepithelial fibroblasts in the jejunal mucosa of adult mice was studied by high resolution light- microscopic radioautography in animals that had received six injections of [3H]thymidine at hourly intervals. During the first 12 hr after exposure to isotope, labeled subepithelial fibroblasts were found only in the crypt region, indicating that only pericryptal fibroblasts synthesized DNA and proliferated. By 24 hr, labeled fibroblasts were seen in the proximal and middle thirds of the villi, and by 36 hr, labeled fibroblasts first appeared in the distal third of the villi. Thus, there appeared to be migration of subepithelial fibroblasts from the pericryptal lamina through the subepithelial tissues of the villi toward the villous tips. In contrast, endothelial cells were labeled at all levels of the mucosa 6 hr after exposure to [3H]thymidine, indicating that these cells are capable of proliferation regardless of their location within the mucosa. Fibroblasts and epithelial cells migrated in synchrony to the base of the villi; thereafter, labeled fibroblasts appeared to migrate more rapidly to the tips of villi than did labeled epithelial cells.