Expression Pattern of LGR5, a Recently Described Intestinal Stem Cell Marker, in Human Duodenum and Duodenal Adenomas
AC Iuga, G Levi, M Sabour, V Ghali, N Theise. St. Luke's Roosevelt Hospital Center and Beth Israel Medical Center, New York, NY
Background: No well-defined marker of human intestinal stem cells has been described. Previously suggested stem cell markers have been too broadly expressed to be specific and the role of stem cells in intestinal neoplasia remains to be determined. LGR5, an orphan G-protein coupled receptor related to glycoprotein hormone ligands such as TSH, FSH and LH receptors, has been identified as a Wnt target gene with restricted crypt expression. In murine studies, the LGR5+ crypt based columnar cells (CBCs) show features unique to stem cells: label-retention, pluripotency, and the capacity to maintain epithelial renewal over extended periods of time. We aim to evaluate expression of LGR5 in human small intestine and contrast this with its expression in adenomatous proliferations of the duodenum.
Design: 10 cases of duodenal tubular adenomas and 7 controls (unremarkable duodenum, chronic duodenitis) were analyzed by LGR5 immunohistochemistry. The specificity of the antibody (Abcam, Cambridge, MA) was confirmed by blocking it with the immunogenic peptide. We strictly defined LGR5+ CBCs as cells with crisp membranous and finely granular cytoplasmic staining. We analyzed LGR5+ non-adenomatous versus adenomatous transversally sectioned glands comparing the ratio of positive cells to the total number of cells per gland between the two groups. Statistical significance was assessed with student T-test.
Results: Duodenum stains positive for LGR5+ CBCs with a particular morphology: slender pyramidal cells with large nucleus and few delicate apical projections, located mostly, but not exclusively, in the crypt base. In normal duodenum, there are 1-2 LGR5+ CBCs in a positive gland (5 LGR5+ CBCs per 100 cells). 6/10 duodenal tubular adenomas showed areas with an absolute increased number of LGR5+ cells (12 LGR5+ CBCs in 100 cells), averaging 10 CBCs per positive adenomatous gland. This difference between non-adenomatous and adenomatous glands was significant (p<0.05). Four adenomas showed no staining.
Conclusions: Based on previous mouse studies, LGR5 immunostaining in normal human duodenum confirms the presence of intestinal stem cells and highlights their morphologic characteristics. The increased absolute number of LGR5+ cells in positive adenomatous glands suggests that dysregulation of stem cell activity may be involved in duodenal adenoma pathogenesis. The lack of staining in some adenomas could be explained by sampling or may be indicative of non-stem cell pathways for adenoma development.
Monday, March 9, 2009 9:30 AM
Poster Session I Stowell-Orbison/Autopsy Award # 97, Monday Morning