Objective: For continuous regeneration of human endometrium in menstrual cycles, endometrial stem cells are assumed to supply differentiating endometrial glandular cells. To elucidate the origin of endometrial stem cells, we examined the presence of donor-derived cells in endometria from patients who received bone marrow transplantation from male donors.
Study design: Endometrial specimens biopsied after hormone replacement therapy were obtained and examined using fluorescent in situ hybridization analysis targeting X or Y chromosomes.
Results: All recipients had donor-derived Y chromosome-positive endometrial cells, accounting for 0.6-8.4% of glandular epithelial cells and 8.2-9.8% of stromal cells. Most of the endometrial glands were chimeric, consisting of both donor-derived and recipient cells.
Conclusion: Donor-derived cells are capable of composing endometrium in recipients, even those of the opposite sex. These results suggest unexpected plasticity of bone marrow stem cells as well as a potential origin of endometrial stem cells.