The endometrium is the inner lining of the uterus. Every month, the endometrium thickens, then matures, and unless the woman becomes pregnant, the mature endometrium degenerates. This is known as the menstrual cycle and it is regulated by changing levels of two female hormones, estrogen and progesterone.

This monthly menstrual cycle is disrupted by diseases of the uterus, such as endometrial atrophy (thinning of the lining) and endometrial cancer. In the past, these diseases could not be fully studied because of the lack of good culture models of the endometrial tissue.

In a new study published in the journal Development, scientists at KU Leuven (University of Leuven), Belgium, show that individual or small group of cells from uterus biopsies can be made to grow into three-dimensional structures in a lab dish. This new technique allows the extensive examination of the endometrial organoids that are now bigger in size compared to the endometrial biopsies that are usually very small.

The scientists were also able to mimic the menstrual cycle in a dish. The researchers reported that the three-dimensional structures showed many features of the womb lining, including the ability to produce mucus. These endometrial organoids respond to the female hormones estrogen (this thickens the tissue), and progesterone (this induces maturation of the tissue), in a way similar to the endometrium in the body. The subsequent removal of the two hormones mimics the shedding of the menstrual cycle. The endometrial organoids represent only a part of the uterus. The researchers hope that it will soon be possible to grow the endometrial organoids together with other cells, for a complete model of the uterus.

According to Hugo Vankelekom, the lead author on this study, aside from successfully expanding the size of endometrial biopsies, thereby allowing an extensive study of the endometrium and the menstrual cycle, their method will also make it possible for researchers to grow endometrial organoids from patients with uterine diseases. This will lead to an extensive study of the malfunctions of the endometrium, which will further lead to better treatment of uterine diseases such as endometrial cancer and endometrial atrophy, as well as fertility problems. This study will be very helpful in testing the efficiency and toxicity of drugs.