Background: Little is known about the stem cell organisation of the normal oesophagus or Barrett's metaplastic oesophagus. Using non-pathogenic mitochondrial DNA mutations as clonal markers, the authors reveal the stem cell organisation of the human squamous oesophagus and of Barrett's metaplasia and determine the mechanism of clonal expansion of mutations.
Methods: Mutated cells were identified using enzyme histochemistry to detect activity of cytochrome c oxidase (CCO). CCO-deficient cells were laser-captured and mutations confirmed by PCR sequencing. Cell lineages were identified using immunohistochemistry.
Results: The normal squamous oesophagus contained CCO-deficient patches varying in size from around 30 μm up to about 1 mm. These patches were clonal as each area within a CCO-deficient patch contained an identical mitochondrial DNA mutation. In Barrett's metaplasia partially CCO-deficient glands indicate that glands are maintained by multiple stem cells. Wholly mutated Barrett's metaplasia glands containing all the expected differentiated cell lineages were seen, demonstrating multilineage differentiation from a clonal population of Barrett's metaplasia stem cells. Patches of clonally mutated Barrett's metaplasia glands were observed, indicating glands can divide to form patches. In one patient, both the regenerating squamous epithelium and the underlying glandular tissue shared a clonal mutation, indicating that they are derived from a common progenitor cell.
Conclusion: In normal oesophageal squamous epithelium, a single stem cell clone can populate large areas of epithelium. Barrett's metaplasia glands are clonal units, contain multiple multipotential stem cells and most likely divide by fission. Furthermore, a single cell of origin can give rise to both squamous and glandular epithelium suggesting oesophageal plasticity.