Identification of Lineage-Uncommitted, Long-Lived, Label-Retaining Cells in Healthy Human Esophagus and Stomach, and in Metaplastic Esophagus

Abstract

Background & Aims:The existence of slowly-cycling, adult stem cells has been challenged by the identification of actively cycling cells. We investigated the existence of uncommitted, slowly cycling cells by tracking 5-iodo-2'-deoxyuridine (IdU) label-retaining cells (LRCs) in normal esophagus, Barrett's esophagus (BE), esophageal dysplasia, adenocarcinoma, and healthy stomach tissues from patients.Methods: Four patients (3 undergoing esophagectomy, 1 undergoing esophageal endoscopic mucosal resection for dysplasia and an esophagectomy for esophageal adenocarcinoma) received intravenous infusion of IdU (200 mg per m 2 body surface area, maximum dose of 400 mg) over a 30-min period; the IdU had a circulation t 1/2 of 8hs. Tissues were collected at 7, 11, 29 and 67 days following infusion, from regions of healthy esophagus, BE, dysplasia, adenocarcinoma, and healthy stomach; they were analyzed by in situ hybridization, flow cytometry, and immunohistochemical analyses. Results:No LRCs were found in dysplasias or adenocarcinomas, but there were significant numbers of LRCs in the base of glands from BE tissue, in the papillae of the basal layer of the esophageal squamous epithelium, and in the neck/isthmus region of healthy stomach. These cells cycled slowly, because IdU was retained for at least 67 days and co-labeling with Ki-67 was infrequent. In glands from BE tissues, most cells did not express defensin-5, Muc-2, or chromogranin A, indicating that they were not lineage committed. Some cells labeled for endocrine markers and IdU at 67 days; these cells represented a small population (<0.1%) of epithelial cells at this timepoint. The epithelial turnover time of the healthy esophageal mucosa was approximately 11 days (twice that of the intestine). Conclusions:LRCs of human esophagus and stomach have many features of stem cells (long lived, slow cycling, uncommitted, and multipotent), and can be found in a recognized stem cell niche. Further analyses of these cells, in healthy and metaplastic epithelia is required.4

Identification and genetic manipulation of human and mouse oesophageal stem cells

“…have observed that oesophageal and lung epithelial cells can change marker expression as early as the first in vitro passage (data not shown), underscoring the importance of analysing cells immediately after removal from patients. Previous studies have suggested the presence of CD34 expressing quiescent basal stem cells in papilla tips of the human oesophageal epithelium 5 9. However, these cells did not show greater clonogenicity compared with other epithelial subpopulations including suprabasal cells, suggesting they may not be enriched for stem cells.…”

Esophageal development and epithelial homeostasis

“…This suggests that a population of label-retaining stem cells may indeed be absent from the murine esophageal epithelium. In humans such a LRC might be present, since one study described the identification of LRCs after 5-iodo-2=-deoxyuridine labeling in patients undergoing esophagectomy (63).…”

Mechanisms of Barrett's oesophagus: Intestinal differentiation, stem cells, and tissue models

“…In a very novel in vivo study in humans, a rare slow-cycling LRC population, representing <0.1% of epithelial cells, has been detected in the crypt base in BE. Moreover, >99% of these LRC do not express lineage-specific markers such as defensin-5, MUC2 and chromogranin A (44). BE stem cells have also been investigated in a mouse model with genetic fate mapping, identifying a Lgr5+ gastric cardia stem cell which may serve as the stem cell in this BE-like metaplasia (45).…”