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World J Gastroenterol. Dec 21, 2008; 14(47): 7160-7162
Published online Dec 21, 2008. doi: 10.3748/wjg.14.7160
Crypt region localization of intestinal stem cells in adults
Hugh James Freeman
Hugh James Freeman, Department of Medicine (Gastroen-terology), University of British Columbia, Vancouver V6T 1W5, Canada
Author contributions: Freeman HJ contributed all to this paper.
Correspondence to: Dr. Hugh James Freeman, MD, FRCPC, FACP, Department of Medicine (Gastroenterology), University of British Columbia Hospital, 2211 Wesbrook Mall, Vancouver V6T 1W5, Canada. hugfree@shaw.ca
Telephone: +1-604-8227216 Fax: +1-604-8227236
Received: August 30, 2008
Revised: October 23, 2008
Accepted: October 30, 2008
Published online: December 21, 2008
Abstract

The intestinal epithelial lining plays a central role in the digestion and absorption of nutrients, but exists in a harsh luminal environment that necessitates continual renewal. This renewal process involves epithelial cell proliferation in the crypt base and later cell migration from the crypt base to the luminal surface. This process is dependent on multi-potent progenitor cells, or stem cells, located in each crypt. There are about 4 to 6 stem cells per crypt, and these stem cells are believed to generate distinct end-differentiated epithelial cell types, including absorptive cells, goblet cells, enteroendocrine cells and Paneth cells, while also maintaining their own progenitor cell state. Earlier studies suggested that intestinal stem cells were located either in the crypt base interspersed between the Paneth cells [i.e. crypt base columnar (CBC) cell model] or at an average position of 4 cells from the crypt base [i.e. label-retaining cells (LRC +4) model]. Recent studies have employed biomarkers in the in vivo mammalian state to more precisely evaluate the location of these progenitor cells in the intestinal crypt. Most notable of these novel markers are Lgr5, a gene that encodes a G-protein-coupled receptor with expression restricted to CBC cells, and Bmi 1, which encodes a chromatin remodeling protein expressed by LRC. These studies raise the possibility that there may be separate stem cell lines or different states of stem cell activation involved in the renewal of normal mammalian intestinal tract.

Keywords: Crypt base columnar cells, Intestinal epithelial cell renewal, Lgr5 gene, Polycomb bmi1 protein, Progenitor cells, Stem cells, +4 stem cell model