Figure 1.

Illustration of stem cell populations in the myometrium and fibroid tissue. Stem cells are self-renewing and are involved in the proliferation of both normal myometrium and fibroid tissue. It is thought that a genetic hit, such as a mutation in the MED12 gene, can lead to the transformation of a myometrial stem cell into a fibroid stem cell. Fibroids are hormone-responsive tissues. However, fibroid stem cells, which are mainly responsible for proliferation and fibroid growth, are devoid of estrogen and progesterone receptors. Thus, stem cell replication and growth is likely regulated via paracrine signals, which lead to fibroid growth. ERα indicates estrogen receptor alpha; PR, progesterone receptor.