The cells came from the endometrium, which lines the inside of the uterus. Endometrium has a deeper basal layer that remains intact and an upper functional layer that is shed during menstruation.

The cells typically surround blood vessels and play a vital role in repairing and regenerating the top layer of tissue that is sheds each month. The researchers' hypothesis is that one of the factors contributes to endometriosis, a painful disease that affects 190 million women and girls around the world.